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              <title>Source Level Debugging with LLVM</title>

            
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            <div class="doc_title">Source Level Debugging with LLVM</div>


            <table class="layout" style="width:100%">

            
              <tr class="layout">

            
                <td class="left">

            
            <ul>

            
              <li><a href="#introduction">Introduction</a>

            
              <ol>

            
                <li><a href="#phil">Philosophy behind LLVM debugging information</a></li>

            
                <li><a href="#consumers">Debug information consumers</a></li>

            
                <li><a href="#debugopt">Debugging optimized code</a></li>

            
              </ol></li>

            
              <li><a href="#format">Debugging information format</a>

            
              <ol>

            
                <li><a href="#debug_info_descriptors">Debug information descriptors</a>

            
                <ul>

            
                  <li><a href="#format_compile_units">Compile unit descriptors</a></li>

            
                  <li><a href="#format_global_variables">Global variable descriptors</a></li>

            
                  <li><a href="#format_subprograms">Subprogram descriptors</a></li>

            
                  <li><a href="#format_blocks">Block descriptors</a></li>

            
                  <li><a href="#format_basic_type">Basic type descriptors</a></li>

            
                  <li><a href="#format_derived_type">Derived type descriptors</a></li>

            
                  <li><a href="#format_composite_type">Composite type descriptors</a></li>

            
                  <li><a href="#format_subrange">Subrange descriptors</a></li>

            
                  <li><a href="#format_enumeration">Enumerator descriptors</a></li>

            
                  <li><a href="#format_variables">Local variables</a></li>

            
                </ul></li>

            
                <li><a href="#format_common_intrinsics">Debugger intrinsic functions</a>

            
                  <ul>

            
                  <li><a href="#format_common_stoppoint">llvm.dbg.stoppoint</a></li>

            
                  <li><a href="#format_common_func_start">llvm.dbg.func.start</a></li>

            
                  <li><a href="#format_common_region_start">llvm.dbg.region.start</a></li>

            
                  <li><a href="#format_common_region_end">llvm.dbg.region.end</a></li>

            
                  <li><a href="#format_common_declare">llvm.dbg.declare</a></li>

            
                </ul></li>

            
                <li><a href="#format_common_stoppoints">Representing stopping points in the

            
                                                       source program</a></li>

            
              </ol></li>

            
              <li><a href="#ccxx_frontend">C/C++ front-end specific debug information</a>

            
              <ol>

            
                <li><a href="#ccxx_compile_units">C/C++ source file information</a></li>

            
                <li><a href="#ccxx_global_variable">C/C++ global variable information</a></li>

            
                <li><a href="#ccxx_subprogram">C/C++ function information</a></li>

            
                <li><a href="#ccxx_basic_types">C/C++ basic types</a></li>

            
                <li><a href="#ccxx_derived_types">C/C++ derived types</a></li>

            
                <li><a href="#ccxx_composite_types">C/C++ struct/union types</a></li>

            
                <li><a href="#ccxx_enumeration_types">C/C++ enumeration types</a></li>

            
              </ol></li>

            
            </ul>

            
            </td>

            
            <td class="right">

            
            <img src="img/venusflytrap.jpg" alt="A leafy and green bug eater" width="247"

            
            height="369">

            
            </td>

            
            </tr></table>


            <div class="doc_author">

            
              <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>

            
                        and <a href="mailto:jlaskey@mac.com">Jim Laskey</a></p>

            
            </div>


            <!-- *********************************************************************** -->

            
            <div class="doc_section"><a name="introduction">Introduction</a></div>

            
            <!-- *********************************************************************** -->


            <div class="doc_text">


            <p>This document is the central repository for all information pertaining to

            
               debug information in LLVM.  It describes the <a href="#format">actual format

            
               that the LLVM debug information</a> takes, which is useful for those

            
               interested in creating front-ends or dealing directly with the information.

            
               Further, this document provides specific examples of what debug information

            
               for C/C++.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="phil">Philosophy behind LLVM debugging information</a>

            
            </div>


            <div class="doc_text">


            <p>The idea of the LLVM debugging information is to capture how the important

            
               pieces of the source-language's Abstract Syntax Tree map onto LLVM code.

            
               Several design aspects have shaped the solution that appears here.  The

            
               important ones are:</p>


            <ul>

            
              <li>Debugging information should have very little impact on the rest of the

            
                  compiler.  No transformations, analyses, or code generators should need to

            
                  be modified because of debugging information.</li>


              <li>LLVM optimizations should interact in <a href="#debugopt">well-defined and

            
                  easily described ways</a> with the debugging information.</li>


              <li>Because LLVM is designed to support arbitrary programming languages,

            
                  LLVM-to-LLVM tools should not need to know anything about the semantics of

            
                  the source-level-language.</li>


              <li>Source-level languages are often <b>widely</b> different from one another.

            
                  LLVM should not put any restrictions of the flavor of the source-language,

            
                  and the debugging information should work with any language.</li>


              <li>With code generator support, it should be possible to use an LLVM compiler

            
                  to compile a program to native machine code and standard debugging

            
                  formats.  This allows compatibility with traditional machine-code level

            
                  debuggers, like GDB or DBX.</li>

            
            </ul>


            <p>The approach used by the LLVM implementation is to use a small set

            
               of <a href="#format_common_intrinsics">intrinsic functions</a> to define a

            
               mapping between LLVM program objects and the source-level objects.  The

            
               description of the source-level program is maintained in LLVM global

            
               variables in an <a href="#ccxx_frontend">implementation-defined format</a>

            
               (the C/C++ front-end currently uses working draft 7 of

            
               the <a href="http://www.eagercon.com/dwarf/dwarf3std.htm">DWARF 3

            
               standard</a>).</p>


            <p>When a program is being debugged, a debugger interacts with the user and

            
               turns the stored debug information into source-language specific information.

            
               As such, a debugger must be aware of the source-language, and is thus tied to

            
               a specific language or family of languages.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="consumers">Debug information consumers</a>

            
            </div>


            <div class="doc_text">


            <p>The role of debug information is to provide meta information normally

            
               stripped away during the compilation process.  This meta information provides

            
               an LLVM user a relationship between generated code and the original program

            
               source code.</p>


            <p>Currently, debug information is consumed by the DwarfWriter to produce dwarf

            
               information used by the gdb debugger.  Other targets could use the same

            
               information to produce stabs or other debug forms.</p>


            <p>It would also be reasonable to use debug information to feed profiling tools

            
               for analysis of generated code, or, tools for reconstructing the original

            
               source from generated code.</p>


            <p>TODO - expound a bit more.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="debugopt">Debugging optimized code</a>

            
            </div>


            <div class="doc_text">


            <p>An extremely high priority of LLVM debugging information is to make it

            
               interact well with optimizations and analysis.  In particular, the LLVM debug

            
               information provides the following guarantees:</p>


            <ul>

            
              <li>LLVM debug information <b>always provides information to accurately read

            
                  the source-level state of the program</b>, regardless of which LLVM

            
                  optimizations have been run, and without any modification to the

            
                  optimizations themselves.  However, some optimizations may impact the

            
                  ability to modify the current state of the program with a debugger, such

            
                  as setting program variables, or calling functions that have been

            
                  deleted.</li>


              <li>LLVM optimizations gracefully interact with debugging information.  If

            
                  they are not aware of debug information, they are automatically disabled

            
                  as necessary in the cases that would invalidate the debug info.  This

            
                  retains the LLVM features, making it easy to write new

            
                  transformations.</li>


              <li>As desired, LLVM optimizations can be upgraded to be aware of the LLVM

            
                  debugging information, allowing them to update the debugging information

            
                  as they perform aggressive optimizations.  This means that, with effort,

            
                  the LLVM optimizers could optimize debug code just as well as non-debug

            
                  code.</li>


              <li>LLVM debug information does not prevent many important optimizations from

            
                  happening (for example inlining, basic block reordering/merging/cleanup,

            
                  tail duplication, etc), further reducing the amount of the compiler that

            
                  eventually is "aware" of debugging information.</li>


              <li>LLVM debug information is automatically optimized along with the rest of

            
                  the program, using existing facilities.  For example, duplicate

            
                  information is automatically merged by the linker, and unused information

            
                  is automatically removed.</li>

            
            </ul>


            <p>Basically, the debug information allows you to compile a program with

            
               "<tt>-O0 -g</tt>" and get full debug information, allowing you to arbitrarily

            
               modify the program as it executes from a debugger.  Compiling a program with

            
               "<tt>-O3 -g</tt>" gives you full debug information that is always available

            
               and accurate for reading (e.g., you get accurate stack traces despite tail

            
               call elimination and inlining), but you might lose the ability to modify the

            
               program and call functions where were optimized out of the program, or

            
               inlined away completely.</p>


            <p><a href="TestingGuide.html#quicktestsuite">LLVM test suite</a> provides a

            
               framework to test optimizer's handling of debugging information. It can be

            
               run like this:</p>


            <div class="doc_code">

            
            <pre>

            
            % cd llvm/projects/test-suite/MultiSource/Benchmarks  # or some other level

            
            % make TEST=dbgopt

            
            </pre>

            
            </div>


            <p>This will test impact of debugging information on optimization passes. If

            
               debugging information influences optimization passes then it will be reported

            
               as a failure. See <a href="TestingGuide.html">TestingGuide</a> for more

            
               information on LLVM test infrastructure and how to run various tests.</p>


            </div>


            <!-- *********************************************************************** -->

            
            <div class="doc_section">

            
              <a name="format">Debugging information format</a>

            
            </div>

            
            <!-- *********************************************************************** -->


            <div class="doc_text">


            <p>LLVM debugging information has been carefully designed to make it possible

            
               for the optimizer to optimize the program and debugging information without

            
               necessarily having to know anything about debugging information.  In

            
               particular, the global constant merging pass automatically eliminates

            
               duplicated debugging information (often caused by header files), the global

            
               dead code elimination pass automatically deletes debugging information for a

            
               function if it decides to delete the function, and the linker eliminates

            
               debug information when it merges <tt>linkonce</tt> functions.</p>


            <p>To do this, most of the debugging information (descriptors for types,

            
               variables, functions, source files, etc) is inserted by the language

            
               front-end in the form of LLVM global variables.  These LLVM global variables

            
               are no different from any other global variables, except that they have a web

            
               of LLVM intrinsic functions that point to them.  If the last references to a

            
               particular piece of debugging information are deleted (for example, by the

            
               <tt>-globaldce</tt> pass), the extraneous debug information will

            
               automatically become dead and be removed by the optimizer.</p>


            <p>Debug information is designed to be agnostic about the target debugger and

            
               debugging information representation (e.g. DWARF/Stabs/etc).  It uses a

            
               generic machine debug information pass to decode the information that

            
               represents variables, types, functions, namespaces, etc: this allows for

            
               arbitrary source-language semantics and type-systems to be used, as long as

            
               there is a module written for the target debugger to interpret the

            
               information. In addition, debug global variables are declared in

            
               the <tt>"llvm.metadata"</tt> section.  All values declared in this section

            
               are stripped away after target debug information is constructed and before

            
               the program object is emitted.</p>


            <p>To provide basic functionality, the LLVM debugger does have to make some

            
               assumptions about the source-level language being debugged, though it keeps

            
               these to a minimum.  The only common features that the LLVM debugger assumes

            
               exist are <a href="#format_compile_units">source files</a>,

            
               and <a href="#format_global_variables">program objects</a>.  These abstract

            
               objects are used by a debugger to form stack traces, show information about

            
               local variables, etc.</p>


            <p>This section of the documentation first describes the representation aspects

            
               common to any source-language.  The <a href="#ccxx_frontend">next section</a>

            
               describes the data layout conventions used by the C and C++ front-ends.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="debug_info_descriptors">Debug information descriptors</a>

            
            </div>


            <div class="doc_text">


            <p>In consideration of the complexity and volume of debug information, LLVM

            
               provides a specification for well formed debug global variables.  The

            
               constant value of each of these globals is one of a limited set of

            
               structures, known as debug descriptors.</p>


            <p>Consumers of LLVM debug information expect the descriptors for program

            
               objects to start in a canonical format, but the descriptors can include

            
               additional information appended at the end that is source-language

            
               specific. All LLVM debugging information is versioned, allowing backwards

            
               compatibility in the case that the core structures need to change in some

            
               way.  Also, all debugging information objects start with a tag to indicate

            
               what type of object it is.  The source-language is allowed to define its own

            
               objects, by using unreserved tag numbers.  We recommend using with tags in

            
               the range 0x1000 thru 0x2000 (there is a defined enum DW_TAG_user_base =

            
               0x1000.)</p>


            <p>The fields of debug descriptors used internally by LLVM (MachineModuleInfo)

            
               are restricted to only the simple data types <tt>int</tt>, <tt>uint</tt>,

            
               <tt>bool</tt>, <tt>float</tt>, <tt>double</tt>, <tt>i8*</tt> and

            
               <tt>{&nbsp;}*</tt>.  References to arbitrary values are handled using a

            
               <tt>{&nbsp;}*</tt> and a cast to <tt>{&nbsp;}*</tt> expression; typically

            
               references to other field descriptors, arrays of descriptors or global

            
               variables.</p>


            <div class="doc_code">

            
            <pre>

            
            %llvm.dbg.object.type = type {

            
              uint,   ;; A tag

            
              ...

            
            }

            
            </pre>

            
            </div>


            <p><a name="LLVMDebugVersion">The first field of a descriptor is always an

            
               <tt>uint</tt> containing a tag value identifying the content of the

            
               descriptor.  The remaining fields are specific to the descriptor.  The values

            
               of tags are loosely bound to the tag values of DWARF information entries.

            
               However, that does not restrict the use of the information supplied to DWARF

            
               targets.  To facilitate versioning of debug information, the tag is augmented

            
               with the current debug version (LLVMDebugVersion = 4 << 16 or 0x40000 or

            
               262144.)</a></p>


            <p>The details of the various descriptors follow.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_compile_units">Compile unit descriptors</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = type {

            
              i32,    ;; Tag = 17 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_compile_unit)

            
              {  }*,  ;; Compile unit anchor = cast = (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to {  }*)

            
              i32,    ;; DWARF language identifier (ex. DW_LANG_C89)

            
              i8*,    ;; Source file name

            
              i8*,    ;; Source file directory (includes trailing slash)

            
              i8*     ;; Producer (ex. "4.0.1 LLVM (LLVM research group)")

            
              i1,     ;; True if this is a main compile unit.

            
              i1,     ;; True if this is optimized.

            
              i8*,    ;; Flags

            
              i32     ;; Runtime version

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors contain a source language ID for the file (we use the DWARF

            
               3.0 ID numbers, such as <tt>DW_LANG_C89</tt>, <tt>DW_LANG_C_plus_plus</tt>,

            
               <tt>DW_LANG_Cobol74</tt>, etc), three strings describing the filename,

            
               working directory of the compiler, and an identifier string for the compiler

            
               that produced it.</p>


            <p>Compile unit descriptors provide the root context for objects declared in a

            
               specific source file.  Global variables and top level functions would be

            
               defined using this context. Compile unit descriptors also provide context

            
               for source line correspondence.</p>


            <p>Each input file is encoded as a separate compile unit in LLVM debugging

            
               information output. However, many target specific tool chains prefer to

            
               encode only one compile unit in an object file. In this situation, the LLVM

            
               code generator will include debugging information entities in the compile

            
               unit that is marked as main compile unit. The code generator accepts maximum

            
               one main compile unit per module. If a module does not contain any main

            
               compile unit then the code generator will emit multiple compile units in the

            
               output object file.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_global_variables">Global variable descriptors</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_global_variables">llvm.dbg.global_variable.type</a> = type {

            
              i32,    ;; Tag = 52 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_variable)

            
              {  }*,  ;; Global variable anchor = cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_global_variables">llvm.dbg.global_variables</a> to {  }*),

            
              {  }*,  ;; Reference to context descriptor

            
              i8*,    ;; Name

            
              i8*,    ;; Display name (fully qualified C++ name)

            
              i8*,    ;; MIPS linkage name (for C++)

            
              {  }*,  ;; Reference to compile unit where defined

            
              i32,    ;; Line number where defined

            
              {  }*,  ;; Reference to type descriptor

            
              i1,     ;; True if the global is local to compile unit (static)

            
              i1,     ;; True if the global is defined in the compile unit (not extern)

            
              {  }*   ;; Reference to the global variable

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors provide debug information about globals variables.  The

            
            provide details such as name, type and where the variable is defined.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_subprograms">Subprogram descriptors</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_subprograms">llvm.dbg.subprogram.type</a> = type {

            
              i32,    ;; Tag = 46 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subprogram)

            
              {  }*,  ;; Subprogram anchor = cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_subprograms">llvm.dbg.subprograms</a> to {  }*),

            
              {  }*,  ;; Reference to context descriptor

            
              i8*,    ;; Name

            
              i8*,    ;; Display name (fully qualified C++ name)

            
              i8*,    ;; MIPS linkage name (for C++)

            
              {  }*,  ;; Reference to compile unit where defined

            
              i32,    ;; Line number where defined

            
              {  }*,  ;; Reference to type descriptor

            
              i1,     ;; True if the global is local to compile unit (static)

            
              i1      ;; True if the global is defined in the compile unit (not extern)

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors provide debug information about functions, methods and

            
               subprograms.  They provide details such as name, return types and the source

            
               location where the subprogram is defined.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_blocks">Block descriptors</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_blocks">llvm.dbg.block</a> = type {

            
              i32,    ;; Tag = 13 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_lexical_block)

            
              {  }*   ;; Reference to context descriptor

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors provide debug information about nested blocks within a

            
               subprogram.  The array of member descriptors is used to define local

            
               variables and deeper nested blocks.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_basic_type">Basic type descriptors</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype.type</a> = type {

            
              i32,    ;; Tag = 36 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_base_type)

            
              {  }*,  ;; Reference to context (typically a compile unit)

            
              i8*,    ;; Name (may be "" for anonymous types)

            
              {  }*,  ;; Reference to compile unit where defined (may be NULL)

            
              i32,    ;; Line number where defined (may be 0)

            
              i64,    ;; Size in bits

            
              i64,    ;; Alignment in bits

            
              i64,    ;; Offset in bits

            
              i32,    ;; Flags

            
              i32     ;; DWARF type encoding

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors define primitive types used in the code. Example int, bool

            
               and float.  The context provides the scope of the type, which is usually the

            
               top level.  Since basic types are not usually user defined the compile unit

            
               and line number can be left as NULL and 0.  The size, alignment and offset

            
               are expressed in bits and can be 64 bit values.  The alignment is used to

            
               round the offset when embedded in a

            
               <a href="#format_composite_type">composite type</a> (example to keep float

            
               doubles on 64 bit boundaries.) The offset is the bit offset if embedded in

            
               a <a href="#format_composite_type">composite type</a>.</p>


            <p>The type encoding provides the details of the type.  The values are typically

            
               one of the following:</p>


            <div class="doc_code">

            
            <pre>

            
            DW_ATE_address       = 1

            
            DW_ATE_boolean       = 2

            
            DW_ATE_float         = 4

            
            DW_ATE_signed        = 5

            
            DW_ATE_signed_char   = 6

            
            DW_ATE_unsigned      = 7

            
            DW_ATE_unsigned_char = 8

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_derived_type">Derived type descriptors</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> = type {

            
              i32,    ;; Tag (see below)

            
              {  }*,  ;; Reference to context

            
              i8*,    ;; Name (may be "" for anonymous types)

            
              {  }*,  ;; Reference to compile unit where defined (may be NULL)

            
              i32,    ;; Line number where defined (may be 0)

            
              i32,    ;; Size in bits

            
              i32,    ;; Alignment in bits

            
              i32,    ;; Offset in bits

            
              {  }*   ;; Reference to type derived from

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors are used to define types derived from other types.  The

            
            value of the tag varies depending on the meaning.  The following are possible

            
            tag values:</p>


            <div class="doc_code">

            
            <pre>

            
            DW_TAG_formal_parameter = 5

            
            DW_TAG_member           = 13

            
            DW_TAG_pointer_type     = 15

            
            DW_TAG_reference_type   = 16

            
            DW_TAG_typedef          = 22

            
            DW_TAG_const_type       = 38

            
            DW_TAG_volatile_type    = 53

            
            DW_TAG_restrict_type    = 55

            
            </pre>

            
            </div>


            <p><tt>DW_TAG_member</tt> is used to define a member of

            
               a <a href="#format_composite_type">composite type</a>

            
               or <a href="#format_subprograms">subprogram</a>.  The type of the member is

            
               the <a href="#format_derived_type">derived

            
               type</a>. <tt>DW_TAG_formal_parameter</tt> is used to define a member which

            
               is a formal argument of a subprogram.</p>


            <p><tt>DW_TAG_typedef</tt> is used to provide a name for the derived type.</p>


            <p><tt>DW_TAG_pointer_type</tt>,<tt>DW_TAG_reference_type</tt>,

            
               <tt>DW_TAG_const_type</tt>, <tt>DW_TAG_volatile_type</tt>

            
               and <tt>DW_TAG_restrict_type</tt> are used to qualify

            
               the <a href="#format_derived_type">derived type</a>. </p>


            <p><a href="#format_derived_type">Derived type</a> location can be determined

            
               from the compile unit and line number.  The size, alignment and offset are

            
               expressed in bits and can be 64 bit values.  The alignment is used to round

            
               the offset when embedded in a <a href="#format_composite_type">composite

            
               type</a> (example to keep float doubles on 64 bit boundaries.) The offset is

            
               the bit offset if embedded in a <a href="#format_composite_type">composite

            
               type</a>.</p>


            <p>Note that the <tt>void *</tt> type is expressed as a

            
               <tt>llvm.dbg.derivedtype.type</tt> with tag of <tt>DW_TAG_pointer_type</tt>

            
               and <tt>NULL</tt> derived type.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_composite_type">Composite type descriptors</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> = type {

            
              i32,    ;; Tag (see below)

            
              {  }*,  ;; Reference to context

            
              i8*,    ;; Name (may be "" for anonymous types)

            
              {  }*,  ;; Reference to compile unit where defined (may be NULL)

            
              i32,    ;; Line number where defined (may be 0)

            
              i64,    ;; Size in bits

            
              i64,    ;; Alignment in bits

            
              i64,    ;; Offset in bits

            
              i32,    ;; Flags

            
              {  }*,  ;; Reference to type derived from

            
              {  }*,  ;; Reference to array of member descriptors

            
              i32     ;; Runtime languages

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors are used to define types that are composed of 0 or more

            
            elements.  The value of the tag varies depending on the meaning.  The following

            
            are possible tag values:</p>


            <div class="doc_code">

            
            <pre>

            
            DW_TAG_array_type       = 1

            
            DW_TAG_enumeration_type = 4

            
            DW_TAG_structure_type   = 19

            
            DW_TAG_union_type       = 23

            
            DW_TAG_vector_type      = 259

            
            DW_TAG_subroutine_type  = 21

            
            DW_TAG_inheritance      = 28

            
            </pre>

            
            </div>


            <p>The vector flag indicates that an array type is a native packed vector.</p>


            <p>The members of array types (tag = <tt>DW_TAG_array_type</tt>) or vector types

            
               (tag = <tt>DW_TAG_vector_type</tt>) are <a href="#format_subrange">subrange

            
               descriptors</a>, each representing the range of subscripts at that level of

            
               indexing.</p>


            <p>The members of enumeration types (tag = <tt>DW_TAG_enumeration_type</tt>) are

            
               <a href="#format_enumeration">enumerator descriptors</a>, each representing

            
               the definition of enumeration value for the set.</p>


            <p>The members of structure (tag = <tt>DW_TAG_structure_type</tt>) or union (tag

            
               = <tt>DW_TAG_union_type</tt>) types are any one of

            
               the <a href="#format_basic_type">basic</a>,

            
               <a href="#format_derived_type">derived</a>

            
               or <a href="#format_composite_type">composite</a> type descriptors, each

            
               representing a field member of the structure or union.</p>


            <p>For C++ classes (tag = <tt>DW_TAG_structure_type</tt>), member descriptors

            
               provide information about base classes, static members and member

            
               functions. If a member is a <a href="#format_derived_type">derived type

            
               descriptor</a> and has a tag of <tt>DW_TAG_inheritance</tt>, then the type

            
               represents a base class. If the member of is

            
               a <a href="#format_global_variables">global variable descriptor</a> then it

            
               represents a static member.  And, if the member is

            
               a <a href="#format_subprograms">subprogram descriptor</a> then it represents

            
               a member function.  For static members and member

            
               functions, <tt>getName()</tt> returns the members link or the C++ mangled

            
               name.  <tt>getDisplayName()</tt> the simplied version of the name.</p>


            <p>The first member of subroutine (tag = <tt>DW_TAG_subroutine_type</tt>) type

            
               elements is the return type for the subroutine.  The remaining elements are

            
               the formal arguments to the subroutine.</p>


            <p><a href="#format_composite_type">Composite type</a> location can be

            
               determined from the compile unit and line number.  The size, alignment and

            
               offset are expressed in bits and can be 64 bit values.  The alignment is used

            
               to round the offset when embedded in

            
               a <a href="#format_composite_type">composite type</a> (as an example, to keep

            
               float doubles on 64 bit boundaries.) The offset is the bit offset if embedded

            
               in a <a href="#format_composite_type">composite type</a>.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_subrange">Subrange descriptors</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_subrange">llvm.dbg.subrange.type</a> = type {

            
              i32,    ;; Tag = 33 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_subrange_type)

            
              i64,    ;; Low value

            
              i64     ;; High value

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors are used to define ranges of array subscripts for an array

            
               <a href="#format_composite_type">composite type</a>.  The low value defines

            
               the lower bounds typically zero for C/C++.  The high value is the upper

            
               bounds.  Values are 64 bit.  High - low + 1 is the size of the array.  If low

            
               == high the array will be unbounded.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_enumeration">Enumerator descriptors</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> = type {

            
              i32,    ;; Tag = 40 + <a href="#LLVMDebugVersion">LLVMDebugVersion</a> (DW_TAG_enumerator)

            
              i8*,    ;; Name

            
              i64     ;; Value

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors are used to define members of an

            
               enumeration <a href="#format_composite_type">composite type</a>, it

            
               associates the name to the value.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_variables">Local variables</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_variables">llvm.dbg.variable.type</a> = type {

            
              i32,     ;; Tag (see below)

            
              {  }*,   ;; Context

            
              i8*,     ;; Name

            
              {  }*,   ;; Reference to compile unit where defined

            
              i32,     ;; Line number where defined

            
              {  }*    ;; Type descriptor

            
            }

            
            </pre>

            
            </div>


            <p>These descriptors are used to define variables local to a sub program.  The

            
               value of the tag depends on the usage of the variable:</p>


            <div class="doc_code">

            
            <pre>

            
            DW_TAG_auto_variable   = 256

            
            DW_TAG_arg_variable    = 257

            
            DW_TAG_return_variable = 258

            
            </pre>

            
            </div>


            <p>An auto variable is any variable declared in the body of the function.  An

            
               argument variable is any variable that appears as a formal argument to the

            
               function.  A return variable is used to track the result of a function and

            
               has no source correspondent.</p>


            <p>The context is either the subprogram or block where the variable is defined.

            
               Name the source variable name.  Compile unit and line indicate where the

            
               variable was defined. Type descriptor defines the declared type of the

            
               variable.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="format_common_intrinsics">Debugger intrinsic functions</a>

            
            </div>


            <div class="doc_text">


            <p>LLVM uses several intrinsic functions (name prefixed with "llvm.dbg") to

            
               provide debug information at various points in generated code.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_common_stoppoint">llvm.dbg.stoppoint</a>

            
            </div>


            <div class="doc_text">

            
            <pre>

            
              void %<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint, uint, { }* )

            
            </pre>


            <p>This intrinsic is used to provide correspondence between the source file and

            
               the generated code.  The first argument is the line number (base 1), second

            
               argument is the column number (0 if unknown) and the third argument the

            
               source <tt>%<a href="#format_compile_units">llvm.dbg.compile_unit</a>*</tt>

            
               cast to a <tt>{&nbsp;}*</tt>.  Code following a call to this intrinsic will

            
               have been defined in close proximity of the line, column and file. This

            
               information holds until the next call

            
               to <tt>%<a href="#format_common_stoppoint">lvm.dbg.stoppoint</a></tt>.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_common_func_start">llvm.dbg.func.start</a>

            
            </div>


            <div class="doc_text">

            
            <pre>

            
              void %<a href="#format_common_func_start">llvm.dbg.func.start</a>( { }* )

            
            </pre>


            <p>This intrinsic is used to link the debug information

            
               in <tt>%<a href="#format_subprograms">llvm.dbg.subprogram</a></tt> to the

            
               function. It defines the beginning of the function's declarative region

            
               (scope). It also implies a call to

            
               %<tt><a href="#format_common_stoppoint">llvm.dbg.stoppoint</a></tt> which

            
               defines a source line "stop point". The intrinsic should be called early in

            
               the function after the all the alloca instructions.  It should be paired off

            
               with a closing

            
               <tt>%<a href="#format_common_region_end">llvm.dbg.region.end</a></tt>.

            
               The function's single argument is

            
               the <tt>%<a href="#format_subprograms">llvm.dbg.subprogram.type</a></tt>.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_common_region_start">llvm.dbg.region.start</a>

            
            </div>


            <div class="doc_text">

            
            <pre>

            
              void %<a href="#format_common_region_start">llvm.dbg.region.start</a>( { }* )

            
            </pre>


            <p>This intrinsic is used to define the beginning of a declarative scope (ex.

            
               block) for local language elements.  It should be paired off with a closing

            
               <tt>%<a href="#format_common_region_end">llvm.dbg.region.end</a></tt>.  The

            
               function's single argument is

            
               the <tt>%<a href="#format_blocks">llvm.dbg.block</a></tt> which is

            
               starting.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_common_region_end">llvm.dbg.region.end</a>

            
            </div>


            <div class="doc_text">

            
            <pre>

            
              void %<a href="#format_common_region_end">llvm.dbg.region.end</a>( { }* )

            
            </pre>


            <p>This intrinsic is used to define the end of a declarative scope (ex. block)

            
               for local language elements.  It should be paired off with an

            
               opening <tt>%<a href="#format_common_region_start">llvm.dbg.region.start</a></tt>

            
               or <tt>%<a href="#format_common_func_start">llvm.dbg.func.start</a></tt>.

            
               The function's single argument is either

            
               the <tt>%<a href="#format_blocks">llvm.dbg.block</a></tt> or

            
               the <tt>%<a href="#format_subprograms">llvm.dbg.subprogram.type</a></tt>

            
               which is ending.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="format_common_declare">llvm.dbg.declare</a>

            
            </div>


            <div class="doc_text">

            
            <pre>

            
              void %<a href="#format_common_declare">llvm.dbg.declare</a>( { } *, { }* )

            
            </pre>


            <p>This intrinsic provides information about a local element (ex. variable.) The

            
               first argument is the alloca for the variable, cast to a <tt>{ }*</tt>. The

            
               second argument is

            
               the <tt>%<a href="#format_variables">llvm.dbg.variable</a></tt> containing

            
               the description of the variable, also cast to a <tt>{ }*</tt>.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="format_common_stoppoints">

            
                 Representing stopping points in the source program

            
              </a>

            
            </div>


            <div class="doc_text">


            <p>LLVM debugger "stop points" are a key part of the debugging representation

            
               that allows the LLVM to maintain simple semantics

            
               for <a href="#debugopt">debugging optimized code</a>.  The basic idea is that

            
               the front-end inserts calls to

            
               the <a href="#format_common_stoppoint">%<tt>llvm.dbg.stoppoint</tt></a>

            
               intrinsic function at every point in the program where a debugger should be

            
               able to inspect the program (these correspond to places a debugger stops when

            
               you "<tt>step</tt>" through it).  The front-end can choose to place these as

            
               fine-grained as it would like (for example, before every subexpression

            
               evaluated), but it is recommended to only put them after every source

            
               statement that includes executable code.</p>


            <p>Using calls to this intrinsic function to demark legal points for the

            
               debugger to inspect the program automatically disables any optimizations that

            
               could potentially confuse debugging information.  To

            
               non-debug-information-aware transformations, these calls simply look like

            
               calls to an external function, which they must assume to do anything

            
               (including reading or writing to any part of reachable memory).  On the other

            
               hand, it does not impact many optimizations, such as code motion of

            
               non-trapping instructions, nor does it impact optimization of subexpressions,

            
               code duplication transformations, or basic-block reordering

            
               transformations.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="format_common_lifetime">Object lifetimes and scoping</a>

            
            </div>


            <div class="doc_text">

            
            <p>In many languages, the local variables in functions can have their lifetime

            
               or scope limited to a subset of a function.  In the C family of languages,

            
               for example, variables are only live (readable and writable) within the

            
               source block that they are defined in.  In functional languages, values are

            
               only readable after they have been defined.  Though this is a very obvious

            
               concept, it is also non-trivial to model in LLVM, because it has no notion of

            
               scoping in this sense, and does not want to be tied to a language's scoping

            
               rules.</p>


            <p>In order to handle this, the LLVM debug format uses the notion of "regions"

            
               of a function, delineated by calls to intrinsic functions.  These intrinsic

            
               functions define new regions of the program and indicate when the region

            
               lifetime expires.  Consider the following C fragment, for example:</p>


            <div class="doc_code">

            
            <pre>

            
            1.  void foo() {

            
            2.    int X = ...;

            
            3.    int Y = ...;

            
            4.    {

            
            5.      int Z = ...;

            
            6.      ...

            
            7.    }

            
            8.    ...

            
            9.  }

            
            </pre>

            
            </div>


            <p>Compiled to LLVM, this function would be represented like this:</p>


            <div class="doc_code">

            
            <pre>

            
            void %foo() {

            
            entry:

            
                %X = alloca int

            
                %Y = alloca int

            
                %Z = alloca int


                ...


                call void @<a href="#format_common_func_start">llvm.dbg.func.start</a>( %<a href="#format_subprograms">llvm.dbg.subprogram.type</a>* @llvm.dbg.subprogram )


                call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 2, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )


                call void @<a href="#format_common_declare">llvm.dbg.declare</a>({}* %X, ...)

            
                call void @<a href="#format_common_declare">llvm.dbg.declare</a>({}* %Y, ...)


                <i>;; Evaluate expression on line 2, assigning to X.</i>


                call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 3, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )


                <i>;; Evaluate expression on line 3, assigning to Y.</i>


                call void @<a href="#format_common_stoppoint">llvm.region.start</a>()

            
                call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 5, uint 4, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )

            
                call void @<a href="#format_common_declare">llvm.dbg.declare</a>({}* %X, ...)


                <i>;; Evaluate expression on line 5, assigning to Z.</i>


                call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 7, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )

            
                call void @<a href="#format_common_region_end">llvm.region.end</a>()


                call void @<a href="#format_common_stoppoint">llvm.dbg.stoppoint</a>( uint 9, uint 2, %<a href="#format_compile_units">llvm.dbg.compile_unit</a>* @llvm.dbg.compile_unit )


                call void @<a href="#format_common_region_end">llvm.region.end</a>()


                ret void

            
            }

            
            </pre>

            
            </div>


            <p>This example illustrates a few important details about the LLVM debugging

            
               information.  In particular, it shows how the various intrinsics are applied

            
               together to allow a debugger to analyze the relationship between statements,

            
               variable definitions, and the code used to implement the function.</p>


            <p>The first

            
               intrinsic <tt>%<a href="#format_common_func_start">llvm.dbg.func.start</a></tt>

            
               provides a link with the <a href="#format_subprograms">subprogram

            
               descriptor</a> containing the details of this function.  This call also

            
               defines the beginning of the function region, bounded by

            
               the <tt>%<a href="#format_common_region_end">llvm.region.end</a></tt> at the

            
               end of the function.  This region is used to bracket the lifetime of

            
               variables declared within.  For a function, this outer region defines a new

            
               stack frame whose lifetime ends when the region is ended.</p>


            <p>It is possible to define inner regions for short term variables by using the

            
               %<a href="#format_common_stoppoint"><tt>llvm.region.start</tt></a>

            
               and <a href="#format_common_region_end"><tt>%llvm.region.end</tt></a> to

            
               bound a region.  The inner region in this example would be for the block

            
               containing the declaration of Z.</p>


            <p>Using regions to represent the boundaries of source-level functions allow

            
               LLVM interprocedural optimizations to arbitrarily modify LLVM functions

            
               without having to worry about breaking mapping information between the LLVM

            
               code and the and source-level program.  In particular, the inliner requires

            
               no modification to support inlining with debugging information: there is no

            
               explicit correlation drawn between LLVM functions and their source-level

            
               counterparts (note however, that if the inliner inlines all instances of a

            
               non-strong-linkage function into its caller that it will not be possible for

            
               the user to manually invoke the inlined function from a debugger).</p>


            <p>Once the function has been defined,

            
               the <a href="#format_common_stoppoint"><tt>stopping point</tt></a>

            
               corresponding to line #2 (column #2) of the function is encountered.  At this

            
               point in the function, <b>no</b> local variables are live.  As lines 2 and 3

            
               of the example are executed, their variable definitions are introduced into

            
               the program using

            
               %<a href="#format_common_declare"><tt>llvm.dbg.declare</tt></a>, without the

            
               need to specify a new region.  These variables do not require new regions to

            
               be introduced because they go out of scope at the same point in the program:

            
               line 9.</p>


            <p>In contrast, the <tt>Z</tt> variable goes out of scope at a different time,

            
               on line 7.  For this reason, it is defined within the inner region, which

            
               kills the availability of <tt>Z</tt> before the code for line 8 is executed.

            
               In this way, regions can support arbitrary source-language scoping rules, as

            
               long as they can only be nested (ie, one scope cannot partially overlap with

            
               a part of another scope).</p>


            <p>It is worth noting that this scoping mechanism is used to control scoping of

            
               all declarations, not just variable declarations.  For example, the scope of

            
               a C++ using declaration is controlled with this and could change how name

            
               lookup is performed.</p>


            </div>


            <!-- *********************************************************************** -->

            
            <div class="doc_section">

            
              <a name="ccxx_frontend">C/C++ front-end specific debug information</a>

            
            </div>

            
            <!-- *********************************************************************** -->


            <div class="doc_text">


            <p>The C and C++ front-ends represent information about the program in a format

            
               that is effectively identical

            
               to <a href="http://www.eagercon.com/dwarf/dwarf3std.htm">DWARF 3.0</a> in

            
               terms of information content.  This allows code generators to trivially

            
               support native debuggers by generating standard dwarf information, and

            
               contains enough information for non-dwarf targets to translate it as

            
               needed.</p>


            <p>This section describes the forms used to represent C and C++ programs. Other

            
               languages could pattern themselves after this (which itself is tuned to

            
               representing programs in the same way that DWARF 3 does), or they could

            
               choose to provide completely different forms if they don't fit into the DWARF

            
               model.  As support for debugging information gets added to the various LLVM

            
               source-language front-ends, the information used should be documented

            
               here.</p>


            <p>The following sections provide examples of various C/C++ constructs and the

            
               debug information that would best describe those constructs.</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="ccxx_compile_units">C/C++ source file information</a>

            
            </div>


            <div class="doc_text">


            <p>Given the source files <tt>MySource.cpp</tt> and <tt>MyHeader.h</tt> located

            
               in the directory <tt>/Users/mine/sources</tt>, the following code:</p>


            <div class="doc_code">

            
            <pre>

            
            #include "MyHeader.h"


            int main(int argc, char *argv[]) {

            
              return 0;

            
            }

            
            </pre>

            
            </div>


            <p>a C/C++ front-end would generate the following descriptors:</p>


            <div class="doc_code">

            
            <pre>

            
            ...

            
            ;;

            
            ;; Define types used.  In this case we need one for compile unit anchors and one

            
            ;; for compile units.

            
            ;;

            
            %<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }

            
            %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = type { uint, {  }*, uint, uint, i8*, i8*, i8* }

            
            ...

            
            ;;

            
            ;; Define the anchor for compile units.  Note that the second field of the

            
            ;; anchor is 17, which is the same as the tag for compile units

            
            ;; (17 = DW_TAG_compile_unit.)

            
            ;;

            
            %<a href="#format_compile_units">llvm.dbg.compile_units</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 17 }, section "llvm.metadata"


            ;;

            
            ;; Define the compile unit for the source file "/Users/mine/sources/MySource.cpp".

            
            ;;

            
            %<a href="#format_compile_units">llvm.dbg.compile_unit1</a> = internal constant %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> {

            
                uint add(uint 17, uint 262144),

            
                {  }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to {  }*),

            
                uint 1,

            
                uint 1,

            
                i8* getelementptr ([13 x i8]* %str1, i32 0, i32 0),

            
                i8* getelementptr ([21 x i8]* %str2, i32 0, i32 0),

            
                i8* getelementptr ([33 x i8]* %str3, i32 0, i32 0) }, section "llvm.metadata"


            ;;

            
            ;; Define the compile unit for the header file "/Users/mine/sources/MyHeader.h".

            
            ;;

            
            %<a href="#format_compile_units">llvm.dbg.compile_unit2</a> = internal constant %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> {

            
                uint add(uint 17, uint 262144),

            
                {  }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_units</a> to {  }*),

            
                uint 1,

            
                uint 1,

            
                i8* getelementptr ([11 x i8]* %str4, int 0, int 0),

            
                i8* getelementptr ([21 x i8]* %str2, int 0, int 0),

            
                i8* getelementptr ([33 x i8]* %str3, int 0, int 0) }, section "llvm.metadata"


            ;;

            
            ;; Define each of the strings used in the compile units.

            
            ;;

            
            %str1 = internal constant [13 x i8] c"MySource.cpp\00", section "llvm.metadata";

            
            %str2 = internal constant [21 x i8] c"/Users/mine/sources/\00", section "llvm.metadata";

            
            %str3 = internal constant [33 x i8] c"4.0.1 LLVM (LLVM research group)\00", section "llvm.metadata";

            
            %str4 = internal constant [11 x i8] c"MyHeader.h\00", section "llvm.metadata";

            
            ...

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="ccxx_global_variable">C/C++ global variable information</a>

            
            </div>


            <div class="doc_text">


            <p>Given an integer global variable declared as follows:</p>


            <div class="doc_code">

            
            <pre>

            
            int MyGlobal = 100;

            
            </pre>

            
            </div>


            <p>a C/C++ front-end would generate the following descriptors:</p>


            <div class="doc_code">

            
            <pre>

            
            ;;

            
            ;; Define types used. One for global variable anchors, one for the global

            
            ;; variable descriptor, one for the global's basic type and one for the global's

            
            ;; compile unit.

            
            ;;

            
            %<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }

            
            %<a href="#format_global_variables">llvm.dbg.global_variable.type</a> = type { uint, {  }*, {  }*, i8*, {  }*, uint, {  }*, bool, bool, {  }*, uint }

            
            %<a href="#format_basic_type">llvm.dbg.basictype.type</a> = type { uint, {  }*, i8*, {  }*, int, uint, uint, uint, uint }

            
            %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = ...

            
            ...

            
            ;;

            
            ;; Define the global itself.

            
            ;;

            
            %MyGlobal = global int 100

            
            ...

            
            ;;

            
            ;; Define the anchor for global variables.  Note that the second field of the

            
            ;; anchor is 52, which is the same as the tag for global variables

            
            ;; (52 = DW_TAG_variable.)

            
            ;;

            
            %<a href="#format_global_variables">llvm.dbg.global_variables</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 52 }, section "llvm.metadata"


            ;;

            
            ;; Define the global variable descriptor.  Note the reference to the global

            
            ;; variable anchor and the global variable itself.

            
            ;;

            
            %<a href="#format_global_variables">llvm.dbg.global_variable</a> = internal constant %<a href="#format_global_variables">llvm.dbg.global_variable.type</a> {

            
                uint add(uint 52, uint 262144),

            
                {  }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_global_variables">llvm.dbg.global_variables</a> to {  }*),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([9 x i8]* %str1, int 0, int 0),

            
                i8* getelementptr ([1 x i8]* %str2, int 0, int 0),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                uint 1,

            
                {  }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to {  }*),

            
                bool false,

            
                bool true,

            
                {  }* cast (int* %MyGlobal to {  }*) }, section "llvm.metadata"


            ;;

            
            ;; Define the basic type of 32 bit signed integer.  Note that since int is an

            
            ;; intrinsic type the source file is NULL and line 0.

            
            ;;

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([4 x i8]* %str3, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                uint 5 }, section "llvm.metadata"


            ;;

            
            ;; Define the names of the global variable and basic type.

            
            ;;

            
            %str1 = internal constant [9 x i8] c"MyGlobal\00", section "llvm.metadata"

            
            %str2 = internal constant [1 x i8] c"\00", section "llvm.metadata"

            
            %str3 = internal constant [4 x i8] c"int\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="ccxx_subprogram">C/C++ function information</a>

            
            </div>


            <div class="doc_text">


            <p>Given a function declared as follows:</p>


            <div class="doc_code">

            
            <pre>

            
            int main(int argc, char *argv[]) {

            
              return 0;

            
            }

            
            </pre>

            
            </div>


            <p>a C/C++ front-end would generate the following descriptors:</p>


            <div class="doc_code">

            
            <pre>

            
            ;;

            
            ;; Define types used. One for subprogram anchors, one for the subprogram

            
            ;; descriptor, one for the global's basic type and one for the subprogram's

            
            ;; compile unit.

            
            ;;

            
            %<a href="#format_subprograms">llvm.dbg.subprogram.type</a> = type { uint, {  }*, {  }*, i8*, {  }*, bool, bool }

            
            %<a href="#format_anchors">llvm.dbg.anchor.type</a> = type { uint, uint }

            
            %<a href="#format_compile_units">llvm.dbg.compile_unit.type</a> = ...


            ;;

            
            ;; Define the anchor for subprograms.  Note that the second field of the

            
            ;; anchor is 46, which is the same as the tag for subprograms

            
            ;; (46 = DW_TAG_subprogram.)

            
            ;;

            
            %<a href="#format_subprograms">llvm.dbg.subprograms</a> = linkonce constant %<a href="#format_anchors">llvm.dbg.anchor.type</a> { uint 0, uint 46 }, section "llvm.metadata"


            ;;

            
            ;; Define the descriptor for the subprogram.  TODO - more details.

            
            ;;

            
            %<a href="#format_subprograms">llvm.dbg.subprogram</a> = internal constant %<a href="#format_subprograms">llvm.dbg.subprogram.type</a> {

            
                uint add(uint 46, uint 262144),

            
                {  }* cast (%<a href="#format_anchors">llvm.dbg.anchor.type</a>* %<a href="#format_subprograms">llvm.dbg.subprograms</a> to {  }*),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([5 x i8]* %str1, int 0, int 0),

            
                i8* getelementptr ([1 x i8]* %str2, int 0, int 0),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                uint 1,

            
                {  }* null,

            
                bool false,

            
                bool true }, section "llvm.metadata"


            ;;

            
            ;; Define the name of the subprogram.

            
            ;;

            
            %str1 = internal constant [5 x i8] c"main\00", section "llvm.metadata"

            
            %str2 = internal constant [1 x i8] c"\00", section "llvm.metadata"


            ;;

            
            ;; Define the subprogram itself.

            
            ;;

            
            int %main(int %argc, i8** %argv) {

            
            ...

            
            }

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="ccxx_basic_types">C/C++ basic types</a>

            
            </div>


            <div class="doc_text">


            <p>The following are the basic type descriptors for C/C++ core types:</p>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_type_bool">bool</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([5 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                uint 2 }, section "llvm.metadata"

            
            %str1 = internal constant [5 x i8] c"bool\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_char">char</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([5 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 8,

            
                uint 8,

            
                uint 0,

            
                uint 6 }, section "llvm.metadata"

            
            %str1 = internal constant [5 x i8] c"char\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_unsigned_char">unsigned char</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([14 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 8,

            
                uint 8,

            
                uint 0,

            
                uint 8 }, section "llvm.metadata"

            
            %str1 = internal constant [14 x i8] c"unsigned char\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_short">short</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([10 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 16,

            
                uint 16,

            
                uint 0,

            
                uint 5 }, section "llvm.metadata"

            
            %str1 = internal constant [10 x i8] c"short int\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_unsigned_short">unsigned short</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([19 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 16,

            
                uint 16,

            
                uint 0,

            
                uint 7 }, section "llvm.metadata"

            
            %str1 = internal constant [19 x i8] c"short unsigned int\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_int">int</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([4 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                uint 5 }, section "llvm.metadata"

            
            %str1 = internal constant [4 x i8] c"int\00", section "llvm.metadata"

            
            </pre></div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_unsigned_int">unsigned int</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([13 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                uint 7 }, section "llvm.metadata"

            
            %str1 = internal constant [13 x i8] c"unsigned int\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_long_long">long long</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([14 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 64,

            
                uint 64,

            
                uint 0,

            
                uint 5 }, section "llvm.metadata"

            
            %str1 = internal constant [14 x i8] c"long long int\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_unsigned_long_long">unsigned long long</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([23 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 64,

            
                uint 64,

            
                uint 0,

            
                uint 7 }, section "llvm.metadata"

            
            %str1 = internal constant [23 x 8] c"long long unsigned int\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_float">float</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([6 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                uint 4 }, section "llvm.metadata"

            
            %str1 = internal constant [6 x i8] c"float\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsubsection">

            
              <a name="ccxx_basic_double">double</a>

            
            </div>


            <div class="doc_text">


            <div class="doc_code">

            
            <pre>

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                8* getelementptr ([7 x 8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 64,

            
                uint 64,

            
                uint 0,

            
                uint 4 }, section "llvm.metadata"

            
            %str1 = internal constant [7 x 8] c"double\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="ccxx_derived_types">C/C++ derived types</a>

            
            </div>


            <div class="doc_text">


            <p>Given the following as an example of C/C++ derived type:</p>


            <div class="doc_code">

            
            <pre>

            
            typedef const int *IntPtr;

            
            </pre>

            
            </div>


            <p>a C/C++ front-end would generate the following descriptors:</p>


            <div class="doc_code">

            
            <pre>

            
            ;;

            
            ;; Define the typedef "IntPtr".

            
            ;;

            
            %<a href="#format_derived_type">llvm.dbg.derivedtype1</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {

            
                uint add(uint 22, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([7 x 8]* %str1, int 0, int 0),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                int 1,

            
                uint 0,

            
                uint 0,

            
                uint 0,

            
                {  }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> to {  }*) }, section "llvm.metadata"

            
            %str1 = internal constant [7 x 8] c"IntPtr\00", section "llvm.metadata"


            ;;

            
            ;; Define the pointer type.

            
            ;;

            
            %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {

            
                uint add(uint 15, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* null,

            
                {  }* null,

            
                int 0,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                {  }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> to {  }*) }, section "llvm.metadata"


            ;;

            
            ;; Define the const type.

            
            ;;

            
            %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {

            
                uint add(uint 38, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* null,

            
                {  }* null,

            
                int 0,

            
                uint 0,

            
                uint 0,

            
                uint 0,

            
                {  }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype1</a> to {  }*) }, section "llvm.metadata"


            ;;

            
            ;; Define the int type.

            
            ;;

            
            %<a href="#format_basic_type">llvm.dbg.basictype1</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                8* getelementptr ([4 x 8]* %str2, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                uint 5 }, section "llvm.metadata"

            
            %str2 = internal constant [4 x 8] c"int\00", section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="ccxx_composite_types">C/C++ struct/union types</a>

            
            </div>


            <div class="doc_text">


            <p>Given the following as an example of C/C++ struct type:</p>


            <div class="doc_code">

            
            <pre>

            
            struct Color {

            
              unsigned Red;

            
              unsigned Green;

            
              unsigned Blue;

            
            };

            
            </pre>

            
            </div>


            <p>a C/C++ front-end would generate the following descriptors:</p>


            <div class="doc_code">

            
            <pre>

            
            ;;

            
            ;; Define basic type for unsigned int.

            
            ;;

            
            %<a href="#format_basic_type">llvm.dbg.basictype</a> = internal constant %<a href="#format_basic_type">llvm.dbg.basictype.type</a> {

            
                uint add(uint 36, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([13 x i8]* %str1, int 0, int 0),

            
                {  }* null,

            
                int 0,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                uint 7 }, section "llvm.metadata"

            
            %str1 = internal constant [13 x i8] c"unsigned int\00", section "llvm.metadata"


            ;;

            
            ;; Define composite type for struct Color.

            
            ;;

            
            %<a href="#format_composite_type">llvm.dbg.compositetype</a> = internal constant %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> {

            
                uint add(uint 19, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([6 x i8]* %str2, int 0, int 0),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                int 1,

            
                uint 96,

            
                uint 32,

            
                uint 0,

            
                {  }* null,

            
                {  }* cast ([3 x {  }*]* %llvm.dbg.array to {  }*) }, section "llvm.metadata"

            
            %str2 = internal constant [6 x i8] c"Color\00", section "llvm.metadata"


            ;;

            
            ;; Define the Red field.

            
            ;;

            
            %<a href="#format_derived_type">llvm.dbg.derivedtype1</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {

            
                uint add(uint 13, uint 262144),

            
                {  }* null,

            
                i8* getelementptr ([4 x i8]* %str3, int 0, int 0),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                int 2,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                {  }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to {  }*) }, section "llvm.metadata"

            
            %str3 = internal constant [4 x i8] c"Red\00", section "llvm.metadata"


            ;;

            
            ;; Define the Green field.

            
            ;;

            
            %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {

            
                uint add(uint 13, uint 262144),

            
                {  }* null,

            
                i8* getelementptr ([6 x i8]* %str4, int 0, int 0),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                int 3,

            
                uint 32,

            
                uint 32,

            
                uint 32,

            
                {  }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to {  }*) }, section "llvm.metadata"

            
            %str4 = internal constant [6 x i8] c"Green\00", section "llvm.metadata"


            ;;

            
            ;; Define the Blue field.

            
            ;;

            
            %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> = internal constant %<a href="#format_derived_type">llvm.dbg.derivedtype.type</a> {

            
                uint add(uint 13, uint 262144),

            
                {  }* null,

            
                i8* getelementptr ([5 x i8]* %str5, int 0, int 0),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                int 4,

            
                uint 32,

            
                uint 32,

            
                uint 64,

            
                {  }* cast (%<a href="#format_basic_type">llvm.dbg.basictype.type</a>* %<a href="#format_basic_type">llvm.dbg.basictype</a> to {  }*) }, section "llvm.metadata"

            
            %str5 = internal constant [5 x 8] c"Blue\00", section "llvm.metadata"


            ;;

            
            ;; Define the array of fields used by the composite type Color.

            
            ;;

            
            %llvm.dbg.array = internal constant [3 x {  }*] [

            
                  {  }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype1</a> to {  }*),

            
                  {  }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype2</a> to {  }*),

            
                  {  }* cast (%<a href="#format_derived_type">llvm.dbg.derivedtype.type</a>* %<a href="#format_derived_type">llvm.dbg.derivedtype3</a> to {  }*) ], section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


            <!-- ======================================================================= -->

            
            <div class="doc_subsection">

            
              <a name="ccxx_enumeration_types">C/C++ enumeration types</a>

            
            </div>


            <div class="doc_text">


            <p>Given the following as an example of C/C++ enumeration type:</p>


            <div class="doc_code">

            
            <pre>

            
            enum Trees {

            
              Spruce = 100,

            
              Oak = 200,

            
              Maple = 300

            
            };

            
            </pre>

            
            </div>


            <p>a C/C++ front-end would generate the following descriptors:</p>


            <div class="doc_code">

            
            <pre>

            
            ;;

            
            ;; Define composite type for enum Trees

            
            ;;

            
            %<a href="#format_composite_type">llvm.dbg.compositetype</a> = internal constant %<a href="#format_composite_type">llvm.dbg.compositetype.type</a> {

            
                uint add(uint 4, uint 262144),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                i8* getelementptr ([6 x i8]* %str1, int 0, int 0),

            
                {  }* cast (%<a href="#format_compile_units">llvm.dbg.compile_unit.type</a>* %<a href="#format_compile_units">llvm.dbg.compile_unit</a> to {  }*),

            
                int 1,

            
                uint 32,

            
                uint 32,

            
                uint 0,

            
                {  }* null,

            
                {  }* cast ([3 x {  }*]* %llvm.dbg.array to {  }*) }, section "llvm.metadata"

            
            %str1 = internal constant [6 x i8] c"Trees\00", section "llvm.metadata"


            ;;

            
            ;; Define Spruce enumerator.

            
            ;;

            
            %<a href="#format_enumeration">llvm.dbg.enumerator1</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {

            
                uint add(uint 40, uint 262144),

            
                i8* getelementptr ([7 x i8]* %str2, int 0, int 0),

            
                int 100 }, section "llvm.metadata"

            
            %str2 = internal constant [7 x i8] c"Spruce\00", section "llvm.metadata"


            ;;

            
            ;; Define Oak enumerator.

            
            ;;

            
            %<a href="#format_enumeration">llvm.dbg.enumerator2</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {

            
                uint add(uint 40, uint 262144),

            
                i8* getelementptr ([4 x i8]* %str3, int 0, int 0),

            
                int 200 }, section "llvm.metadata"

            
            %str3 = internal constant [4 x i8] c"Oak\00", section "llvm.metadata"


            ;;

            
            ;; Define Maple enumerator.

            
            ;;

            
            %<a href="#format_enumeration">llvm.dbg.enumerator3</a> = internal constant %<a href="#format_enumeration">llvm.dbg.enumerator.type</a> {

            
                uint add(uint 40, uint 262144),

            
                i8* getelementptr ([6 x i8]* %str4, int 0, int 0),

            
                int 300 }, section "llvm.metadata"

            
            %str4 = internal constant [6 x i8] c"Maple\00", section "llvm.metadata"


            ;;

            
            ;; Define the array of enumerators used by composite type Trees.

            
            ;;

            
            %llvm.dbg.array = internal constant [3 x {  }*] [

            
              {  }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator1</a> to {  }*),

            
              {  }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator2</a> to {  }*),

            
              {  }* cast (%<a href="#format_enumeration">llvm.dbg.enumerator.type</a>* %<a href="#format_enumeration">llvm.dbg.enumerator3</a> to {  }*) ], section "llvm.metadata"

            
            </pre>

            
            </div>


            </div>


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              <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>

            
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