llvm/docs/CommandGuide/llvm-extract.md

# llvm-extract - extract a function from an LLVM module

```{program} llvm-extract
```

## SYNOPSIS

{program}`llvm-extract` \[*options*\] **--func** *function-name* \[*filename*\]

## DESCRIPTION

The {program}`llvm-extract` command takes the name of a function and extracts
it from the specified LLVM bitcode file. It is primarily used as a debugging
tool to reduce test cases from larger programs that are triggering a bug.

In addition to extracting the bitcode of the specified function,
{program}`llvm-extract` will also remove unreachable global variables,
prototypes, and unused types.

The {program}`llvm-extract` command reads its input from standard input if
filename is omitted or if filename is `-`. The output is always written to
standard output, unless the **-o** option is specified (see below).

## OPTIONS

:::{option} --alias <alias-name>
Extract the alias named *function-name* from the LLVM bitcode. May be
specified multiple times to extract multiple alias at once.
:::

:::{option} --ralias <alias-regular-expr>
Extract the alias matching *alias-regular-expr* from the LLVM bitcode.
All alias matching the regular expression will be extracted. May be
specified multiple times.
:::

:::{option} --bb <basic-block-specifier>
Extract basic blocks(s) specified in *basic-block-specifier*. May be
specified multiple times. Each \<function:bb[;bb]> specifier pair will create
a function. If multiple basic blocks are specified in one pair, the first
block in the sequence should dominate the rest.
:::

:::{option} --delete
Delete specified Globals from Module.
:::

:::{option} -f
Enable binary output on terminals. Normally, {program}`llvm-extract` will
refuse to write raw bitcode output if the output stream is a terminal. With
this option, {program}`llvm-extract` will write raw bitcode regardless of the
output device.
:::

:::{option} --func <function-name>
Extract the function named *function-name* from the LLVM bitcode. May be
specified multiple times to extract multiple functions at once.
:::

:::{option} --rfunc <function-regular-expr>
Extract the function(s) matching *function-regular-expr* from the LLVM bitcode.
All functions matching the regular expression will be extracted. May be
specified multiple times.
:::

:::{option} --glob <global-name>
Extract the global variable named *global-name* from the LLVM bitcode. May be
specified multiple times to extract multiple global variables at once.
:::

:::{option} --rglob <glob-regular-expr>
Extract the global variable(s) matching *global-regular-expr* from the LLVM
bitcode. All global variables matching the regular expression will be
extracted. May be specified multiple times.
:::

:::{option} --keep-const-init
Preserve the values of constant globals.
:::

:::{option} --recursive
Recursively extract all called functions
:::

:::{option} -help
Print a summary of command line options.
:::

:::{option} -o <filename>
Specify the output filename. If filename is "-" (the default), then
{program}`llvm-extract` sends its output to standard output.
:::

:::{option} -S
Write output in LLVM intermediate language (instead of bitcode).
:::

## EXIT STATUS

If {program}`llvm-extract` succeeds, it will exit with 0. Otherwise, if an error
occurs, it will exit with a non-zero value.

## SEE ALSO

{manpage}`llvm-reduce(1)`