[AMDGPU] si-peephole-sdwa: Remove dead code from createSDWAversion

[frederik-h]

In an earlier state of this code, it was possible for an existing SDWA MI to reach the code in the "createSDWAversion" function. This is no longer possible; see assert at the top of the function.

Remove code that tries to handle operands on pre-existing SDWA instructions from the function.

[llvmbot]

@llvm/pr-subscribers-backend-amdgpu

Author: Frederik Harwath (frederik-h)

Changes

In an earlier state of this code, it was possible for an existing SDWA MI to reach the code in the "createSDWAversion" function. This is no longer possible; see assert at the top of the function.

Remove code that tries to handle operands on pre-existing SDWA instructions from the function.

---

Full diff: https://github.com/llvm/llvm-project/pull/141462.diff

1 Files Affected:

• (modified) llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp (+7-50)

diff --git a/llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp b/llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp
index 1e305c2efc8a0..eb18677780803 100644
--- a/llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp
+++ b/llvm/lib/Target/AMDGPU/SIPeepholeSDWA.cpp
@@ -1273,65 +1273,22 @@ MachineInstr *SIPeepholeSDWA::createSDWAVersion(MachineInstr &MI) {
     }
   }
 
-  // Copy dst_sel if present, initialize otherwise if needed
-  if (AMDGPU::hasNamedOperand(SDWAOpcode, AMDGPU::OpName::dst_sel)) {
-    MachineOperand *DstSel = TII->getNamedOperand(MI, AMDGPU::OpName::dst_sel);
-    if (DstSel) {
-      SDWAInst.add(*DstSel);
-    } else {
-      SDWAInst.addImm(AMDGPU::SDWA::SdwaSel::DWORD);
-    }
-  }
+  // Initialize SDWA specific operands
+  if (AMDGPU::hasNamedOperand(SDWAOpcode, AMDGPU::OpName::dst_sel))
+    SDWAInst.addImm(AMDGPU::SDWA::SdwaSel::DWORD);
 
-  // Copy dst_unused if present, initialize otherwise if needed
-  if (AMDGPU::hasNamedOperand(SDWAOpcode, AMDGPU::OpName::dst_unused)) {
-    MachineOperand *DstUnused = TII->getNamedOperand(MI, AMDGPU::OpName::dst_unused);
-    if (DstUnused) {
-      SDWAInst.add(*DstUnused);
-    } else {
-      SDWAInst.addImm(AMDGPU::SDWA::DstUnused::UNUSED_PAD);
-    }
-  }
+  if (AMDGPU::hasNamedOperand(SDWAOpcode, AMDGPU::OpName::dst_unused))
+    SDWAInst.addImm(AMDGPU::SDWA::DstUnused::UNUSED_PAD);
 
-  // Copy src0_sel if present, initialize otherwise
   assert(AMDGPU::hasNamedOperand(SDWAOpcode, AMDGPU::OpName::src0_sel));
-  MachineOperand *Src0Sel = TII->getNamedOperand(MI, AMDGPU::OpName::src0_sel);
-  if (Src0Sel) {
-    SDWAInst.add(*Src0Sel);
-  } else {
-    SDWAInst.addImm(AMDGPU::SDWA::SdwaSel::DWORD);
-  }
+  SDWAInst.addImm(AMDGPU::SDWA::SdwaSel::DWORD);
 
-  // Copy src1_sel if present, initialize otherwise if needed
   if (Src1) {
     assert(AMDGPU::hasNamedOperand(SDWAOpcode, AMDGPU::OpName::src1_sel));
-    MachineOperand *Src1Sel = TII->getNamedOperand(MI, AMDGPU::OpName::src1_sel);
-    if (Src1Sel) {
-      SDWAInst.add(*Src1Sel);
-    } else {
-      SDWAInst.addImm(AMDGPU::SDWA::SdwaSel::DWORD);
-    }
+    SDWAInst.addImm(AMDGPU::SDWA::SdwaSel::DWORD);
   }
 
   // Check for a preserved register that needs to be copied.
-  auto *DstUnused = TII->getNamedOperand(MI, AMDGPU::OpName::dst_unused);
-  if (DstUnused &&
-      DstUnused->getImm() == AMDGPU::SDWA::DstUnused::UNUSED_PRESERVE) {
-    // We expect, if we are here, that the instruction was already in it's SDWA form,
-    // with a tied operand.
-    assert(Dst && Dst->isTied());
-    assert(Opcode == static_cast<unsigned int>(SDWAOpcode));
-    // We also expect a vdst, since sdst can't preserve.
-    auto PreserveDstIdx = AMDGPU::getNamedOperandIdx(SDWAOpcode, AMDGPU::OpName::vdst);
-    assert(PreserveDstIdx != -1);
-
-    auto TiedIdx = MI.findTiedOperandIdx(PreserveDstIdx);
-    auto Tied = MI.getOperand(TiedIdx);
-
-    SDWAInst.add(Tied);
-    SDWAInst->tieOperands(PreserveDstIdx, SDWAInst->getNumOperands() - 1);
-  }
-
   MachineInstr *Ret = SDWAInst.getInstr();
   TII->fixImplicitOperands(*Ret);
   return Ret;

[llvm-ci]

LLVM Buildbot has detected a new failure on builder clang-ppc64-aix running on aix-ppc64 while building llvm at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/64/builds/3837

Here is the relevant piece of the build log for the reference

Step 6 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'lit :: timeout-hang.py' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 13
not env -u FILECHECK_OPTS "/home/llvm/llvm-external-buildbots/workers/env/bin/python3.11" /home/llvm/llvm-external-buildbots/workers/aix-ppc64/clang-ppc64-aix/llvm-project/llvm/utils/lit/lit.py -j1 --order=lexical Inputs/timeout-hang/run-nonexistent.txt  --timeout=1 --param external=0 | "/home/llvm/llvm-external-buildbots/workers/env/bin/python3.11" /home/llvm/llvm-external-buildbots/workers/aix-ppc64/clang-ppc64-aix/build/utils/lit/tests/timeout-hang.py 1
# executed command: not env -u FILECHECK_OPTS /home/llvm/llvm-external-buildbots/workers/env/bin/python3.11 /home/llvm/llvm-external-buildbots/workers/aix-ppc64/clang-ppc64-aix/llvm-project/llvm/utils/lit/lit.py -j1 --order=lexical Inputs/timeout-hang/run-nonexistent.txt --timeout=1 --param external=0
# .---command stderr------------
# | lit.py: /home/llvm/llvm-external-buildbots/workers/aix-ppc64/clang-ppc64-aix/llvm-project/llvm/utils/lit/lit/main.py:72: note: The test suite configuration requested an individual test timeout of 0 seconds but a timeout of 1 seconds was requested on the command line. Forcing timeout to be 1 seconds.
# `-----------------------------
# executed command: /home/llvm/llvm-external-buildbots/workers/env/bin/python3.11 /home/llvm/llvm-external-buildbots/workers/aix-ppc64/clang-ppc64-aix/build/utils/lit/tests/timeout-hang.py 1
# .---command stdout------------
# | Testing took as long or longer than timeout
# `-----------------------------
# error: command failed with exit status: 1

--

********************