diff options
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 19 | ||||
| -rw-r--r-- | llvm/test/Transforms/InstCombine/mul.ll | 20 |
2 files changed, 31 insertions, 8 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 7f152aac52d..a301d9eef60 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -213,6 +213,25 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) { if (Instruction *FoldedMul = foldBinOpIntoSelectOrPhi(I)) return FoldedMul; + // TODO: This is a specific form of a much more general pattern. + // We could detect a select with any binop identity constant, or we + // could use SimplifyBinOp to see if either arm of the select reduces. + // But that needs to be done carefully and/or while removing potential + // reverse canonicalizations as in InstCombiner::foldSelectIntoOp(). + // mul (select Cond, 1, -1), Op1 --> select Cond, Op1, -Op1 + // mul (select Cond, -1, 1), Op1 --> select Cond, -Op1, Op1 + // mul Op0, (select Cond, 1, -1) --> select Cond, Op0, -Op0 + // mul Op0, (select Cond, -1, 1) --> select Cond, -Op0, Op0 + Value *Cond; + if (match(Op0, m_OneUse(m_Select(m_Value(Cond), m_One(), m_AllOnes())))) + return SelectInst::Create(Cond, Op1, Builder.CreateNeg(Op1)); + if (match(Op0, m_OneUse(m_Select(m_Value(Cond), m_AllOnes(), m_One())))) + return SelectInst::Create(Cond, Builder.CreateNeg(Op1), Op1); + if (match(Op1, m_OneUse(m_Select(m_Value(Cond), m_One(), m_AllOnes())))) + return SelectInst::Create(Cond, Op0, Builder.CreateNeg(Op0)); + if (match(Op1, m_OneUse(m_Select(m_Value(Cond), m_AllOnes(), m_One())))) + return SelectInst::Create(Cond, Builder.CreateNeg(Op0), Op0); + // Simplify mul instructions with a constant RHS. if (isa<Constant>(Op1)) { // Canonicalize (X+C1)*CI -> X*CI+C1*CI. diff --git a/llvm/test/Transforms/InstCombine/mul.ll b/llvm/test/Transforms/InstCombine/mul.ll index 37f05d222c9..f106026762b 100644 --- a/llvm/test/Transforms/InstCombine/mul.ll +++ b/llvm/test/Transforms/InstCombine/mul.ll @@ -520,8 +520,8 @@ define i64 @test_mul_canonicalize_neg_is_not_undone(i64 %L1) { define i32 @negate_if_true(i32 %x, i1 %cond) { ; CHECK-LABEL: @negate_if_true( -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], i32 -1, i32 1 -; CHECK-NEXT: [[R:%.*]] = mul i32 [[SEL]], [[X:%.*]] +; CHECK-NEXT: [[TMP1:%.*]] = sub i32 0, [[X:%.*]] +; CHECK-NEXT: [[R:%.*]] = select i1 [[COND:%.*]], i32 [[TMP1]], i32 [[X]] ; CHECK-NEXT: ret i32 [[R]] ; %sel = select i1 %cond, i32 -1, i32 1 @@ -531,8 +531,8 @@ define i32 @negate_if_true(i32 %x, i1 %cond) { define i32 @negate_if_false(i32 %x, i1 %cond) { ; CHECK-LABEL: @negate_if_false( -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], i32 1, i32 -1 -; CHECK-NEXT: [[R:%.*]] = mul i32 [[SEL]], [[X:%.*]] +; CHECK-NEXT: [[TMP1:%.*]] = sub i32 0, [[X:%.*]] +; CHECK-NEXT: [[R:%.*]] = select i1 [[COND:%.*]], i32 [[X]], i32 [[TMP1]] ; CHECK-NEXT: ret i32 [[R]] ; %sel = select i1 %cond, i32 1, i32 -1 @@ -543,8 +543,8 @@ define i32 @negate_if_false(i32 %x, i1 %cond) { define <2 x i8> @negate_if_true_commute(<2 x i8> %px, i1 %cond) { ; CHECK-LABEL: @negate_if_true_commute( ; CHECK-NEXT: [[X:%.*]] = sdiv <2 x i8> <i8 42, i8 42>, [[PX:%.*]] -; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x i8> <i8 -1, i8 -1>, <2 x i8> <i8 1, i8 1> -; CHECK-NEXT: [[R:%.*]] = mul <2 x i8> [[X]], [[SEL]] +; CHECK-NEXT: [[TMP1:%.*]] = sub nsw <2 x i8> zeroinitializer, [[X]] +; CHECK-NEXT: [[R:%.*]] = select i1 [[COND:%.*]], <2 x i8> [[TMP1]], <2 x i8> [[X]] ; CHECK-NEXT: ret <2 x i8> [[R]] ; %x = sdiv <2 x i8> <i8 42, i8 42>, %px ; thwart complexity-based canonicalization @@ -556,8 +556,8 @@ define <2 x i8> @negate_if_true_commute(<2 x i8> %px, i1 %cond) { define <2 x i8> @negate_if_false_commute(<2 x i8> %px, <2 x i1> %cond) { ; CHECK-LABEL: @negate_if_false_commute( ; CHECK-NEXT: [[X:%.*]] = sdiv <2 x i8> <i8 42, i8 5>, [[PX:%.*]] -; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> [[COND:%.*]], <2 x i8> <i8 1, i8 undef>, <2 x i8> <i8 -1, i8 -1> -; CHECK-NEXT: [[R:%.*]] = mul <2 x i8> [[X]], [[SEL]] +; CHECK-NEXT: [[TMP1:%.*]] = sub <2 x i8> zeroinitializer, [[X]] +; CHECK-NEXT: [[R:%.*]] = select <2 x i1> [[COND:%.*]], <2 x i8> [[X]], <2 x i8> [[TMP1]] ; CHECK-NEXT: ret <2 x i8> [[R]] ; %x = sdiv <2 x i8> <i8 42, i8 5>, %px ; thwart complexity-based canonicalization @@ -566,6 +566,8 @@ define <2 x i8> @negate_if_false_commute(<2 x i8> %px, <2 x i1> %cond) { ret <2 x i8> %r } +; Negative test + define i32 @negate_if_true_extra_use(i32 %x, i1 %cond) { ; CHECK-LABEL: @negate_if_true_extra_use( ; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], i32 -1, i32 1 @@ -579,6 +581,8 @@ define i32 @negate_if_true_extra_use(i32 %x, i1 %cond) { ret i32 %r } +; Negative test + define <2 x i8> @negate_if_true_wrong_constant(<2 x i8> %px, i1 %cond) { ; CHECK-LABEL: @negate_if_true_wrong_constant( ; CHECK-NEXT: [[X:%.*]] = sdiv <2 x i8> <i8 42, i8 42>, [[PX:%.*]] |
