[PATCH] D22011: [SystemZ] Generate fewer instructions for (sub <constant>, x)

[Assem Bsoul via llvm-commits]

assem added a comment.

Thanks Ulrich. I have tried to implement what you have suggested in the two-address pass. However, it seems that checking for reg1026 and reg1025 being mapped to the same physical register is very broad and can catch a lot of cases that we don't want to convert to 3-address form.

I have looked at the log file generated by -debug and -print-after-all, and I think that the correct thing to do is to include a pass after register allocation to check for cases where a copy is done after a 2-address instruction. I am not sure if there is a better place to implement this. I appreciate any suggestions.


https://reviews.llvm.org/D22011