[llvm-commits] [PATCH] Add Pattern ID Information

[Chris Lattner]

On Aug 4, 2011, at 6:35 AM, David A. Greene wrote:

> Chris Lattner <clattner at apple.com> writes:
> 
>> On Aug 3, 2011, at 4:38 PM, David Greene wrote:
>>> I've got a patch series ready to implement support for printing asm comments
>>> about instruction selection.  For example:
>>> 
>>>       incq    %rdx                    # test.c:38
>>>                                       #  Src: (add:i64 GR64:i64:$src, 1:i64)
>>>                                       #  Dst: (INC64r:i64 GR64:i64:$src)
>> 
>> Out of curiosity, how is this any better than just listing the
>> 'INC64r' opcode?  We already have that accessible and don't need to
>> add anything to MachineInstr to get it.
> 
> Because sometimes multiple patterns map to an instruction.  Think of
> Pat<> patterns.  It's helpful to know which pattern matched to generate
> the instruction.

I guess I don't see the value in distinguishing which of several possible Pat<> patterns matched a specific instruction.  If you need that level of detail, you'll be looking at dag dumps anyway.

-Chris