[llvm-dev] phys reg liveness during foldMemoryOperandImpl()

Jonas Paulsson via llvm-dev llvm-dev at lists.llvm.org
Fri Apr 15 03:53:29 PDT 2016


I wonder if it would be possible to extend foldMemoryOperandImp() so 
that targets can check for liveness of a particular phys reg?

The case I am thinking of is when the new instruction clobbers the CC 
reg, while the old one did not. In this case the new instruction can 
only become a replacement if the CC reg is known to be dead.

The idea is that liveness of phys regs should be available somehow when 
this functionis called during regalloc. Part of the issue is the fact 
that CC reg is not an allocatable register.

/Jonas Paulsson

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