LLVM TableGen Kernel

This notebook is running llvm-tblgen.

%reset
// This is some tablegen
class Foo {}

------------- Classes -----------------
class Foo {
}
------------- Defs -----------------

Errors printed to stderr are shown.

%reset
This is not tablegen.

<stdin>:1:1: error: Unexpected token at top level
This is not tablegen.
^

Add some classes to get some output.

%reset
class Stuff {}
def thing : Stuff {}

------------- Classes -----------------
class Stuff {
}
------------- Defs -----------------
def thing {	// Stuff
}

By default cells are connected. Meaning that we cache the code and magic directives from the previously run cells.

This means that the next cell still sees the Stuff class.

def other_thing : Stuff {}

------------- Classes -----------------
class Stuff {
}
------------- Defs -----------------
def other_thing {	// Stuff
}
def thing {	// Stuff
}

You can use the magic %reset to clear this cache and start fresh.

%reset
def other_thing : Stuff {}

<stdin>:1:19: error: Couldn't find class 'Stuff'
def other_thing : Stuff {}
                  ^

You can also configure the default reset behaviour using the %config magic.

%config cellreset on
class Thing {}

------------- Classes -----------------
class Thing {
}
------------- Defs -----------------

// The cache is reset here so this is an error.
def AThing: Thing {}

<stdin>:2:13: error: Couldn't find class 'Thing'
def AThing: Thing {}
            ^

The default value is off, meaning cells are connected. If you want to override the default for one cell only, use the %reset or %noreset magic. These always override the default.

class Thing {}

------------- Classes -----------------
class Thing {
}
------------- Defs -----------------

%noreset
// This works because of the noreset above.
def AThing: Thing {}

------------- Classes -----------------
class Thing {
}
------------- Defs -----------------
def AThing {	// Thing
}

// This does not because we're not changing the default.
def AnotherThing: Thing {}

<stdin>:2:19: error: Couldn't find class 'Thing'
def AnotherThing: Thing {}
                  ^

%config cellreset off
%reset
// Here we have an empty cache and default reset behaviour.

------------- Classes -----------------
------------- Defs -----------------

It is not valid to have %reset and %noreset in the same cell.

%reset
%noreset

%reset and %noreset in the same cell is not allowed. Use only one, or neither.

Consider setting cellreset to the majority usecase for your notebook. For example a tutorial building a large example across many cells will likely want it off. One with many standalone examples, on.

There is a “magic” directive %args that you can use to send command line arguments to llvm-tblgen.

For example, here we have some code that shows a warning.

%reset
class Thing <int A, int B> {
    int num = A;
}

<stdin>:1:25: warning: unused template argument: Thing:B
class Thing <int A, int B> {
                        ^

We can pass an argument to ignore that warning.

%args --no-warn-on-unused-template-args

------------- Classes -----------------
class Thing<int Thing:A = ?, int Thing:B = ?> {
  int num = Thing:A;
}
------------- Defs -----------------

If you have a run of cells without a %reset, the most recent %args is used.

// This passes --no-warn-on-unused-template-args

------------- Classes -----------------
class Thing<int Thing:A = ?, int Thing:B = ?> {
  int num = Thing:A;
}
------------- Defs -----------------

%args
// Now we're not passing the argument so the warning comes back.

<stdin>:1:25: warning: unused template argument: Thing:B
class Thing <int A, int B> {
                        ^

If there are many %args in a cell, the last one is used.

%reset
%args --no-warn-on-unused-template-args
%args
class Thing <int A, int B> {}

<stdin>:1:18: warning: unused template argument: Thing:A
class Thing <int A, int B> {}
                 ^
<stdin>:1:25: warning: unused template argument: Thing:B
class Thing <int A, int B> {}
                        ^