[PATCH] D131958: Add all constant physical registers to callee preserved masks

Wed Aug 17 05:58:02 PDT 2022

asb added inline comments.

================
Comment at: llvm/test/CodeGen/RISCV/double-convert.ll:632
 ; RV32I-NEXT:    lui a3, 802304
 ; RV32I-NEXT:    li s2, 0
 ; RV32I-NEXT:    mv a0, s1
----------------
arichardson wrote:
> Still got a load of zero into a saved register here, not quite sure why. `blt s2, s4, .LBB12_4` should be able to use the zero register.
Yes, there's something weird going on in general with selection of the zero register.  See D130809 and [the bug tracking this issue](https://github.com/llvm/llvm-project/issues/56872). I'm not sure if it's a general problem with register coalescer or if there's some hook that's not set properly somewhere.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D131958/new/

https://reviews.llvm.org/D131958