diff options
author | darkbuck <michael.hliao@gmail.com> | 2024-04-03 20:52:21 -0400 |
---|---|---|
committer | GitHub <noreply@github.com> | 2024-04-03 20:52:21 -0400 |
commit | 1f01c580444ea2daef67f95ffc5fde2de5a37cec (patch) | |
tree | 8f09e9c56f0682ddddff1ddf74143750a8d554ec | |
parent | abd05eb4a53e6c7760496620da417733f52d4bf9 (diff) | |
download | llvm-1f01c580444ea2daef67f95ffc5fde2de5a37cec.zip llvm-1f01c580444ea2daef67f95ffc5fde2de5a37cec.tar.gz llvm-1f01c580444ea2daef67f95ffc5fde2de5a37cec.tar.bz2 |
[GlobalISel] Fix the infinite loop issue in `commute_int_constant_to_rhs`
- When both operands are constant, the matcher runs into an infinite
loop as the commutation should be applied only when LHS is a constant
and RHS is not.
Reviewers: arsenm
Reviewed By: arsenm
Pull Request: https://github.com/llvm/llvm-project/pull/87426
-rw-r--r-- | llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp | 17 | ||||
-rw-r--r-- | llvm/test/CodeGen/AArch64/GlobalISel/combine-commute-int-const-lhs.mir | 28 |
2 files changed, 37 insertions, 8 deletions
diff --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp index 5cf7a33..062132c 100644 --- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp +++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp @@ -6276,14 +6276,15 @@ bool CombinerHelper::matchShiftsTooBig(MachineInstr &MI) { bool CombinerHelper::matchCommuteConstantToRHS(MachineInstr &MI) { Register LHS = MI.getOperand(1).getReg(); Register RHS = MI.getOperand(2).getReg(); - 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; + 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. 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 new file mode 100644 index 0000000..b145a6d --- /dev/null +++ b/llvm/test/CodeGen/AArch64/GlobalISel/combine-commute-int-const-lhs.mir @@ -0,0 +1,28 @@ +# 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 + +... |