[llvm-dev] phys reg liveness during foldMemoryOperandImpl()
Jonas Paulsson via llvm-dev
llvm-dev at lists.llvm.org
Wed Apr 27 11:38:01 PDT 2016
Either this can be implemented easily, or the current SystemZ
optimization LAY -> AGSI in foldMemoryOperandImpl() should be removed,
since this is actually illegal.
On 2016-04-15 12:53, Jonas Paulsson wrote:
> 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
More information about the llvm-dev