diff options
Diffstat (limited to 'llvm')
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp | 10 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/add.ll | 10 |
2 files changed, 14 insertions, 6 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp index 659b6c326c5..3709360226f 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -1079,6 +1079,16 @@ static Instruction *foldAddWithConstant(BinaryOperator &Add, return new ZExtInst(Builder.CreateNUWAdd(X, NewC), Ty); } + // Shifts and add used to flip and mask off the low bit: + // add (ashr (shl i32 X, 31), 31), 1 --> and (not X), 1 + const APInt *C3; + if (*C == 1 && match(Op0, m_OneUse(m_AShr(m_Shl(m_Value(X), m_APInt(C2)), + m_APInt(C3)))) && + C2 == C3 && *C2 == Ty->getScalarSizeInBits() - 1) { + Value *NotX = Builder.CreateNot(X); + return BinaryOperator::CreateAnd(NotX, ConstantInt::get(Ty, 1)); + } + return nullptr; } diff --git a/llvm/test/Transforms/InstCombine/add.ll b/llvm/test/Transforms/InstCombine/add.ll index 955ffaaeecd..5f7101e8fec 100644 --- a/llvm/test/Transforms/InstCombine/add.ll +++ b/llvm/test/Transforms/InstCombine/add.ll @@ -31,9 +31,8 @@ define <2 x i32> @select_0_or_1_from_bool_vec(<2 x i1> %x) { define i32 @flip_and_mask(i32 %x) { ; CHECK-LABEL: @flip_and_mask( -; CHECK-NEXT: [[SHL:%.*]] = shl i32 %x, 31 -; CHECK-NEXT: [[SHR:%.*]] = ashr exact i32 [[SHL]], 31 -; CHECK-NEXT: [[INC:%.*]] = add nsw i32 [[SHR]], 1 +; CHECK-NEXT: [[TMP1:%.*]] = and i32 %x, 1 +; CHECK-NEXT: [[INC:%.*]] = xor i32 [[TMP1]], 1 ; CHECK-NEXT: ret i32 [[INC]] ; %shl = shl i32 %x, 31 @@ -44,9 +43,8 @@ define i32 @flip_and_mask(i32 %x) { define <2 x i8> @flip_and_mask_splat(<2 x i8> %x) { ; CHECK-LABEL: @flip_and_mask_splat( -; CHECK-NEXT: [[SHL:%.*]] = shl <2 x i8> %x, <i8 7, i8 7> -; CHECK-NEXT: [[SHR:%.*]] = ashr exact <2 x i8> [[SHL]], <i8 7, i8 7> -; CHECK-NEXT: [[INC:%.*]] = add nsw <2 x i8> [[SHR]], <i8 1, i8 1> +; CHECK-NEXT: [[TMP1:%.*]] = xor <2 x i8> %x, <i8 1, i8 1> +; CHECK-NEXT: [[INC:%.*]] = and <2 x i8> [[TMP1]], <i8 1, i8 1> ; CHECK-NEXT: ret <2 x i8> [[INC]] ; %shl = shl <2 x i8> %x, <i8 7, i8 7> |
