[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:
> Hi,
> 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 mailing list