Index: lib/Transforms/InstCombine/InstructionCombining.cpp =================================================================== --- lib/Transforms/InstCombine/InstructionCombining.cpp +++ lib/Transforms/InstCombine/InstructionCombining.cpp @@ -731,6 +731,7 @@ Value *SI = nullptr; if (match(LHS, m_Select(m_Value(A), m_Value(B), m_Value(C))) && match(RHS, m_Select(m_Specific(A), m_Value(D), m_Value(E)))) { + bool SelectsHaveOneUse = LHS->hasOneUse() && RHS->hasOneUse(); BuilderTy::FastMathFlagGuard Guard(Builder); if (isa(&I)) Builder.setFastMathFlags(I.getFastMathFlags()); @@ -739,9 +740,9 @@ Value *V2 = SimplifyBinOp(Opcode, B, D, SQ.getWithInstruction(&I)); if (V1 && V2) SI = Builder.CreateSelect(A, V2, V1); - else if (V2) + else if (V2 && SelectsHaveOneUse) SI = Builder.CreateSelect(A, V2, Builder.CreateBinOp(Opcode, C, E)); - else if (V1) + else if (V1 && SelectsHaveOneUse) SI = Builder.CreateSelect(A, Builder.CreateBinOp(Opcode, B, D), V1); if (SI) Index: test/Transforms/InstCombine/select_arithmetic.ll =================================================================== --- test/Transforms/InstCombine/select_arithmetic.ll +++ test/Transforms/InstCombine/select_arithmetic.ll @@ -3,17 +3,32 @@ target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128" ; Tests folding constants from two similar selects that feed a add -define float @test1(i1 zeroext %arg) #0 { +define float @test1a(i1 zeroext %arg) #0 { %tmp = select i1 %arg, float 5.000000e+00, float 6.000000e+00 %tmp1 = select i1 %arg, float 1.000000e+00, float 9.000000e+00 %tmp2 = fadd float %tmp, %tmp1 ret float %tmp2 -; CHECK-LABEL: @test1( +; CHECK-LABEL: @test1a( ; CHECK: %tmp2 = select i1 %arg, float 6.000000e+00, float 1.500000e+01 ; CHECK-NOT: fadd ; CHECK: ret float %tmp2 } +; Tests folding multiple expression constants from similar selects that feed a adds +define float @test1b(i1 zeroext %arg) #0 { + %tmp = select i1 %arg, float 5.000000e+00, float 6.000000e+00 + %tmp1 = select i1 %arg, float 1.000000e+00, float 9.000000e+00 + %tmp2 = select i1 %arg, float 2.500000e-01, float 4.000000e+00 + %tmp3 = fadd float %tmp, %tmp1 + %tmp4 = fadd float %tmp2, %tmp1 + %tmp5 = fadd float %tmp4, %tmp3 + ret float %tmp5 +; CHECK-LABEL: @test1b( +; CHECK: %tmp5 = select i1 %arg, float 7.250000e+00, float 2.800000e+01 +; CHECK-NOT: fadd +; CHECK: ret float %tmp5 +} + ; Tests folding constants from two similar selects that feed a sub define float @test2(i1 zeroext %arg) #0 { %tmp = select i1 %arg, float 5.000000e+00, float 6.000000e+00