[all-commits] [llvm/llvm-project] c3cbd2: [AMDGPU] Calc IsVALU correctly during UADDO/USUBO ...

[LU-JOHN via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c3cbd27d005b86ea5c5a375c21b86e6c2110e198
      https://github.com/llvm/llvm-project/commit/c3cbd27d005b86ea5c5a375c21b86e6c2110e198
  Author: LU-JOHN <John.Lu at amd.com>
  Date:   2025-09-25 (Thu, 25 Sep 2025)

  Changed paths:
    M llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp
    M llvm/lib/Target/AMDGPU/SIISelLowering.cpp
    M llvm/test/CodeGen/AMDGPU/amdgpu-codegenprepare-idiv.ll
    M llvm/test/CodeGen/AMDGPU/carryout-selection.ll
    M llvm/test/CodeGen/AMDGPU/expand-scalar-carry-out-select-user.ll
    A llvm/test/CodeGen/AMDGPU/s_uaddo_usubo_pseudo.ll
    M llvm/test/CodeGen/AMDGPU/sdiv64.ll
    M llvm/test/CodeGen/AMDGPU/srem.ll
    M llvm/test/CodeGen/AMDGPU/srem64.ll
    M llvm/test/CodeGen/AMDGPU/udiv64.ll
    M llvm/test/CodeGen/AMDGPU/urem64.ll
    M llvm/test/CodeGen/AMDGPU/wave32.ll

  Log Message:
  -----------
  [AMDGPU] Calc IsVALU correctly during UADDO/USUBO selection (#159814)

Fix two bugs.  The first bug hid the second bug.

1. Calculate IsVALU correctly during UADDO/USUBO selection. IsVALU
should be false if the carryout users are UADDO_CARRY/USUBO_CARRY.
However instruction selection visits uses before defs, so the
UADDO_CARRY/USUBO_CARRY nodes are normally (probably always) already
converted to S_ADD_CO_PSEUDO/S_SUB_CO_PSEUDO. Fix to check for these
machine opcodes.

2. Without this fix, UADDO/USUBO selection will always select the VALU
instructions V_ADD_CO__U32_e64/V_SUB_CO_U32_e64.
S_UADDO_PSEUDO/S_USUBO_PSEUDO were never selected in the CodeGen/AMDGPU
tests. Thus, S_UADDO_PSEUDO/S_USUBO_PSEUDO cases were never hit in
EmitInstrWithCustomInserter. The code generation for
S_UADDO_PSEUDO/S_USUBO_PSEUDO had a bug where it could not handle code
generation for 32-bit $scc_out.

---------

Signed-off-by: John Lu <John.Lu at amd.com>
Co-authored-by: Matt Arsenault <arsenm2 at gmail.com>



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