[PATCH] D135948: [LoongArch] Add codegen support for cmpxchg on LA64

[WÁNG Xuěruì via Phabricator via llvm-commits]

xen0n added inline comments.


================
Comment at: llvm/test/CodeGen/LoongArch/ir-instruction/atomic-cmpxchg.ll:326
+; LA64-NEXT:  .LBB10_4:
+; LA64-NEXT:    bstrpick.d $a0, $a1, 31, 0
+; LA64-NEXT:    xor $a0, $a3, $a0
----------------
This seems wrong: the following `xor` insn responsible for the `same value -> 0` part operates on full GRLen, but here `a1` i.e. `%cmp` gets zero-extended to `a0`, yet `a3` i.e. the value from memory is loaded with `ll.w` that sign-extends. I expect this will fail for cases where `cmp == *ptr && cmp < 0`.

Either this should be a sign-extension, or the comparison shouldn't be `xor`.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D135948/new/

https://reviews.llvm.org/D135948