Index: llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp =================================================================== --- llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -1693,8 +1693,11 @@ // 0 - (X sdiv C) -> (X sdiv -C) provided the negation doesn't overflow. if (match(Op1, m_SDiv(m_Value(X), m_Constant(C))) && match(Op0, m_Zero()) && - C->isNotMinSignedValue() && !C->isOneValue()) - return BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C)); + C->isNotMinSignedValue() && !C->isOneValue()) { + auto *BO = BinaryOperator::CreateSDiv(X, ConstantExpr::getNeg(C)); + BO->setIsExact(cast(Op1)->isExact()); + return BO; + } // 0 - (X << Y) -> (-X << Y) when X is freely negatable. if (match(Op1, m_Shl(m_Value(X), m_Value(Y))) && match(Op0, m_Zero())) Index: llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp =================================================================== --- llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -1021,6 +1021,14 @@ return new SExtInst(NarrowOp, Op0->getType()); } } + + // -X / Y --> -(X / Y) + // X / -Y --> -(X / Y) + Value *Y; + if (match(&I, m_SDiv(m_OneUse(m_NSWSub(m_Zero(), m_Value(X))), m_Value(Y))) || + match(&I, m_SDiv(m_Value(X), m_OneUse(m_NSWSub(m_Zero(), m_Value(Y)))))) + return BinaryOperator::CreateNeg( + Builder.CreateSDiv(X, Y, I.getName(), I.isExact())); if (Constant *RHS = dyn_cast(Op1)) { // X/INT_MIN -> X == INT_MIN Index: llvm/test/Transforms/InstCombine/sdiv-canonicalize.ll =================================================================== --- llvm/test/Transforms/InstCombine/sdiv-canonicalize.ll +++ llvm/test/Transforms/InstCombine/sdiv-canonicalize.ll @@ -3,8 +3,8 @@ define i32 @test_sdiv_canonicalize_op0(i32 %x, i32 %y) { ; CHECK-LABEL: @test_sdiv_canonicalize_op0( -; CHECK-NEXT: [[NEG:%.*]] = sub nsw i32 0, [[X:%.*]] -; CHECK-NEXT: [[SDIV:%.*]] = sdiv i32 [[NEG]], [[Y:%.*]] +; CHECK-NEXT: [[NEG:%.*]] = sdiv i32 [[X:%.*]], [[Y:%.*]] +; CHECK-NEXT: [[SDIV:%.*]] = sub i32 0, [[NEG]] ; CHECK-NEXT: ret i32 [[SDIV]] ; %neg = sub nsw i32 0, %x @@ -15,8 +15,8 @@ define i32 @test_sdiv_canonicalize_op1(i32 %x, i32 %z) { ; CHECK-LABEL: @test_sdiv_canonicalize_op1( ; CHECK-NEXT: [[Y:%.*]] = mul i32 [[Z:%.*]], 3 -; CHECK-NEXT: [[NEG:%.*]] = sub nsw i32 0, [[X:%.*]] -; CHECK-NEXT: [[SDIV:%.*]] = sdiv i32 [[Y]], [[NEG]] +; CHECK-NEXT: [[NEG:%.*]] = sdiv i32 [[Y]], [[X:%.*]] +; CHECK-NEXT: [[SDIV:%.*]] = sub i32 0, [[NEG]] ; CHECK-NEXT: ret i32 [[SDIV]] ; %y = mul i32 %z, 3 @@ -38,8 +38,8 @@ define <2 x i32> @test_sdiv_canonicalize_vec(<2 x i32> %x, <2 x i32> %y) { ; CHECK-LABEL: @test_sdiv_canonicalize_vec( -; CHECK-NEXT: [[NEG:%.*]] = sub nsw <2 x i32> zeroinitializer, [[X:%.*]] -; CHECK-NEXT: [[SDIV:%.*]] = sdiv <2 x i32> [[NEG]], [[Y:%.*]] +; CHECK-NEXT: [[NEG:%.*]] = sdiv <2 x i32> [[X:%.*]], [[Y:%.*]] +; CHECK-NEXT: [[SDIV:%.*]] = sub <2 x i32> zeroinitializer, [[NEG]] ; CHECK-NEXT: ret <2 x i32> [[SDIV]] ; %neg = sub nsw <2 x i32> , %x