[PATCH] D11880: AMDGPU/SI: Only look at live out SGPR defs

[Matt Arsenault via llvm-commits]

> On Aug 10, 2015, at 7:46 AM, Tom Stellard via llvm-commits <llvm-commits at lists.llvm.org> wrote:
> 
> tstellarAMD added a comment.
> 
>> When trying to fix SGPR live ranges, skip defs that are
> 
>> killed in the same block as the def. I don't think
> 
>> we need to worry about these cases as long as the
> 
>> live ranges of the SGPRs in dominating blocks are
> 
>> correct.
> 
> 
> I think this will break this case:
> 
> def vreg0 <- assigned sgpr0
> 
> if:
> def vreg1 <- assigned sgpr0
> kill vreg1  <- assigned sgpr0
> br endif
> 
> else:
> use vreg0 <- assigned sgpr0
> br endif
> 
> endif:
> …

I’m not sure I see why. vreg0 is live out of the entry block, so it will have it’s range extended until after the endif, so I don’t think it can be assigned to the same register as vreg1





> 
> 
> http://reviews.llvm.org/D11880
> 
> 
> 
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits