[llvm-commits] [llvm] r126538 - in /llvm/trunk/utils/TableGen: AsmWriterEmitter.cpp AsmWriterEmitter.h

[Chris Lattner]

On May 22, 2011, at 4:58 PM, Bill Wendling wrote:
>> That makes sense for the movsx vs movswl, but the point of this is that tblgen should be able to automatically prune these things out as well.  This is good because it reduces the code size of the generated alias stuff.
>> 
> Okay. The simplest heuristic would be to omit printing an alias which has more operands than the thing it's aliasing. I'll do that and then we can adjust the heuristic afterwards.

This sounds like a great start.  If they have the same number of operands and the mnemonic is longer, then it also makes sense to prune it.

>> What do you mean impossible?  My point is this instruction *always* has zero instructions, so this check is always true and shouldn't be generated.
>> 
> Sure. If I can get the information that an instruction will always take a specific number of instructions, then I'll omit that check.

Ok, tblgen should have this.  Thanks Bill,

-Chris