[llvm] be8fd86 - Revert "[GlobalISel] Fix the infinite loop issue in `commute_int_constant_to_rhs`"

[Gulfem Savrun Yeniceri via llvm-commits]

Author: Gulfem Savrun Yeniceri
Date: 2024-04-04T16:39:31Z
New Revision: be8fd86f6a57da79a4dbc8d1f4dca2e7adb1192a

URL: https://github.com/llvm/llvm-project/commit/be8fd86f6a57da79a4dbc8d1f4dca2e7adb1192a
DIFF: https://github.com/llvm/llvm-project/commit/be8fd86f6a57da79a4dbc8d1f4dca2e7adb1192a.diff

LOG: Revert "[GlobalISel] Fix the infinite loop issue in `commute_int_constant_to_rhs`"

This reverts commit 1f01c580444ea2daef67f95ffc5fde2de5a37cec
because combine-commute-int-const-lhs.mir test failed in
multiple builders.
https://lab.llvm.org/buildbot/#/builders/124/builds/10375
https://luci-milo.appspot.com/ui/p/fuchsia/builders/prod/clang-linux-x64/b8751607530180046481/overview

Added: 
    

Modified: 
    llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

Removed: 
    llvm/test/CodeGen/AArch64/GlobalISel/combine-commute-int-const-lhs.mir


################################################################################
diff  --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
index 719209e0edd5fb..e53e35d98ceca7 100644
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -6273,15 +6273,14 @@ bool CombinerHelper::matchShiftsTooBig(MachineInstr &MI) {
 bool CombinerHelper::matchCommuteConstantToRHS(MachineInstr &MI) {
   Register LHS = MI.getOperand(1).getReg();
   Register RHS = MI.getOperand(2).getReg();
-  if (!getIConstantVRegVal(LHS, MRI)) {
-    // Skip commuting if LHS is not a constant. But, LHS may be a
-    // G_CONSTANT_FOLD_BARRIER. If so we commute as long as we don't already
-    // have a constant on the RHS.
-    if (MRI.getVRegDef(LHS)->getOpcode() !=
-        TargetOpcode::G_CONSTANT_FOLD_BARRIER)
-      return false;
-  }
-  // Commute as long as RHS is not a constant or G_CONSTANT_FOLD_BARRIER.
+  auto *LHSDef = MRI.getVRegDef(LHS);
+  if (getIConstantVRegVal(LHS, MRI).has_value())
+    return true;
+
+  // LHS may be a G_CONSTANT_FOLD_BARRIER. If so we commute
+  // as long as we don't already have a constant on the RHS.
+  if (LHSDef->getOpcode() != TargetOpcode::G_CONSTANT_FOLD_BARRIER)
+    return false;
   return MRI.getVRegDef(RHS)->getOpcode() !=
              TargetOpcode::G_CONSTANT_FOLD_BARRIER &&
          !getIConstantVRegVal(RHS, MRI);

diff  --git a/llvm/test/CodeGen/AArch64/GlobalISel/combine-commute-int-const-lhs.mir b/llvm/test/CodeGen/AArch64/GlobalISel/combine-commute-int-const-lhs.mir
deleted file mode 100644
index b145a6d3fd39d1..00000000000000
--- a/llvm/test/CodeGen/AArch64/GlobalISel/combine-commute-int-const-lhs.mir
+++ /dev/null
@@ -1,28 +0,0 @@
-# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 4
-# RUN: llc -mtriple aarch64 -run-pass=aarch64-prelegalizer-combiner %s -o - \
-# RUN:     --aarch64prelegalizercombiner-disable-rule=constant_fold_binop | FileCheck %s
-
-# `constant_fold_binop` is disabled to trigger the infinite loop in `commute_int_constant_to_rhs`.
-
----
-name:            add
-tracksRegLiveness: true
-body:             |
-  bb.0:
-    liveins: $s0
-
-    ; CHECK-LABEL: name: add
-    ; CHECK: liveins: $s0
-    ; CHECK-NEXT: {{  $}}
-    ; CHECK-NEXT: %c0:_(s32) = G_CONSTANT i32 1
-    ; CHECK-NEXT: %c1:_(s32) = G_CONSTANT i32 2
-    ; CHECK-NEXT: %add:_(s32) = G_ADD %c0, %c1
-    ; CHECK-NEXT: $s0 = COPY %add(s32)
-    ; CHECK-NEXT: RET_ReallyLR
-    %c0:_(s32) = G_CONSTANT i32 1
-    %c1:_(s32) = G_CONSTANT i32 2
-    %add:_(s32) = G_ADD %c0, %c1
-    $s0 = COPY %add
-    RET_ReallyLR
-
-...