[AArch64] xor -1 can be mvn, so make it free #166014
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@llvm/pr-subscribers-backend-aarch64 Author: AZero13 (AZero13) ChangesFull diff: https://github.com/llvm/llvm-project/pull/166014.diff 1 Files Affected:
diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index fede586cf35bc..bd25a81f9025a 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -443,6 +443,10 @@ InstructionCost AArch64TTIImpl::getIntImmCostInst(unsigned Opcode, unsigned Idx,
case Instruction::Store:
ImmIdx = 0;
break;
+ case Instruction::Xor:
+ if (Idx == 1 && (BitSize == 32 || BitSize == 64) && Imm.isAllOnes())
+ return TTI::TCC_Free; // xor a, -1 can be folded to MVN
+ [[fallthrough]];
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
@@ -452,7 +456,6 @@ InstructionCost AArch64TTIImpl::getIntImmCostInst(unsigned Opcode, unsigned Idx,
case Instruction::SRem:
case Instruction::And:
case Instruction::Or:
- case Instruction::Xor:
case Instruction::ICmp:
ImmIdx = 1;
break;
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You can test this locally with the following command:git-clang-format --diff origin/main HEAD --extensions cpp -- llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp --diff_from_common_commit
View the diff from clang-format here.diff --git a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
index ffe297acb..53c8c235a 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
@@ -446,7 +446,7 @@ InstructionCost AArch64TTIImpl::getIntImmCostInst(unsigned Opcode, unsigned Idx,
case Instruction::Xor:
if (Imm.isAllOnes())
return TTI::TCC_Free; // xor a, -1 can be folded to MVN
- [[fallthrough]];
+ [[fallthrough]];
case Instruction::Add:
case Instruction::Sub:
case Instruction::Mul:
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