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[InstCombine] Fold fcmp into select (llvm#86482)
This patch simplifies `fcmp (select Cond, C1, C2), C3` patterns in ceres: Alive2: https://alive2.llvm.org/ce/z/fWh_sD ``` define i1 @src(double %x) { %cmp1 = fcmp ord double %x, 0.000000e+00 %sel = select i1 %cmp1, double 0xFFFFFFFFFFFFFFFF, double 0.000000e+00 %cmp2 = fcmp oeq double %sel, 0.000000e+00 ret i1 %cmp2 } define i1 @tgt(double %x) { %cmp1 = fcmp uno double %x, 0.000000e+00 ret i1 %cmp1 } ```
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3 files changed

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‎llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

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Original file line numberDiff line numberDiff line change
@@ -8052,6 +8052,8 @@ Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
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m_Select(m_Value(), m_Value(X), m_FNeg(m_Deferred(X)))) ||
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match(LHSI, m_Select(m_Value(), m_FNeg(m_Value(X)), m_Deferred(X)))))
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return replaceOperand(I, 0, X);
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if (Instruction *NV = FoldOpIntoSelect(I, cast<SelectInst>(LHSI)))
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return NV;
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break;
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case Instruction::PHI:
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if (Instruction *NV = foldOpIntoPhi(I, cast<PHINode>(LHSI)))

‎llvm/test/Transforms/InstCombine/fcmp-select.ll

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Original file line numberDiff line numberDiff line change
@@ -2,6 +2,7 @@
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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declare void @use(i1)
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declare void @usef64(double)
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; X == 42.0 ? X : 42.0 --> 42.0
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@@ -148,3 +149,122 @@ define i1 @fcmp_ogt_select(i1 %cond, float %a, float %b) {
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%res = fcmp ogt float %lhs, %rhs
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ret i1 %res
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}
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define i1 @test_fcmp_select_const_const(double %x) {
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; CHECK-LABEL: @test_fcmp_select_const_const(
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; CHECK-NEXT: [[CMP1:%.*]] = fcmp uno double [[X:%.*]], 0.000000e+00
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; CHECK-NEXT: ret i1 [[CMP1]]
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;
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%cmp1 = fcmp ord double %x, 0.000000e+00
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%sel = select i1 %cmp1, double 0xFFFFFFFFFFFFFFFF, double 0.000000e+00
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%cmp2 = fcmp oeq double %sel, 0.000000e+00
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ret i1 %cmp2
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}
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define i1 @test_fcmp_select_var_const(double %x, double %y) {
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; CHECK-LABEL: @test_fcmp_select_var_const(
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; CHECK-NEXT: [[CMP1:%.*]] = fcmp ule double [[X:%.*]], 0x3E80000000000000
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; CHECK-NEXT: [[TMP1:%.*]] = fcmp olt double [[Y:%.*]], 0x3E80000000000000
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; CHECK-NEXT: [[CMP2:%.*]] = select i1 [[CMP1]], i1 true, i1 [[TMP1]]
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; CHECK-NEXT: ret i1 [[CMP2]]
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;
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%cmp1 = fcmp ogt double %x, 0x3E80000000000000
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%sel = select i1 %cmp1, double %y, double 0.000000e+00
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%cmp2 = fcmp olt double %sel, 0x3E80000000000000
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ret i1 %cmp2
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}
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define i1 @test_fcmp_select_var_const_fmf(double %x, double %y) {
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; CHECK-LABEL: @test_fcmp_select_var_const_fmf(
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; CHECK-NEXT: [[CMP1:%.*]] = fcmp ule double [[X:%.*]], 0x3E80000000000000
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; CHECK-NEXT: [[TMP1:%.*]] = fcmp nnan olt double [[Y:%.*]], 0x3E80000000000000
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; CHECK-NEXT: [[CMP2:%.*]] = select i1 [[CMP1]], i1 true, i1 [[TMP1]]
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; CHECK-NEXT: ret i1 [[CMP2]]
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;
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%cmp1 = fcmp ogt double %x, 0x3E80000000000000
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%sel = select i1 %cmp1, double %y, double 0.000000e+00
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%cmp2 = fcmp nnan olt double %sel, 0x3E80000000000000
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ret i1 %cmp2
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}
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define <2 x i1> @test_fcmp_select_const_const_vec(<2 x double> %x) {
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; CHECK-LABEL: @test_fcmp_select_const_const_vec(
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; CHECK-NEXT: [[CMP1:%.*]] = fcmp uno <2 x double> [[X:%.*]], zeroinitializer
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; CHECK-NEXT: ret <2 x i1> [[CMP1]]
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;
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%cmp1 = fcmp ord <2 x double> %x, zeroinitializer
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%sel = select <2 x i1> %cmp1, <2 x double> <double 0xFFFFFFFFFFFFFFFF, double 0xFFFFFFFFFFFFFFFF>, <2 x double> zeroinitializer
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%cmp2 = fcmp oeq <2 x double> %sel, zeroinitializer
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ret <2 x i1> %cmp2
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}
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; Don't break clamp idioms
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define double @test_fcmp_select_clamp(double %x) {
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; CHECK-LABEL: @test_fcmp_select_clamp(
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; CHECK-NEXT: [[CMP1:%.*]] = fcmp ogt double [[X:%.*]], 9.000000e-01
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; CHECK-NEXT: [[SEL1:%.*]] = select i1 [[CMP1]], double 9.000000e-01, double [[X]]
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; CHECK-NEXT: [[CMP2:%.*]] = fcmp olt double [[SEL1]], 5.000000e-01
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; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[CMP2]], double 5.000000e-01, double [[SEL1]]
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; CHECK-NEXT: ret double [[SEL2]]
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;
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%cmp1 = fcmp ogt double %x, 9.000000e-01
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%sel1 = select i1 %cmp1, double 9.000000e-01, double %x
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%cmp2 = fcmp olt double %sel1, 5.000000e-01
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%sel2 = select i1 %cmp2, double 5.000000e-01, double %sel1
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ret double %sel2
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}
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; Don't break fmin/fmax idioms
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define double @test_fcmp_select_maxnum(double %x) {
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; CHECK-LABEL: @test_fcmp_select_maxnum(
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; CHECK-NEXT: [[SEL1:%.*]] = call nnan nsz double @llvm.maxnum.f64(double [[X:%.*]], double 1.000000e+00)
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; CHECK-NEXT: [[SEL2:%.*]] = call nnan nsz double @llvm.minnum.f64(double [[SEL1]], double 2.550000e+02)
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; CHECK-NEXT: ret double [[SEL2]]
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;
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%cmp1 = fcmp ogt double %x, 1.0
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%sel1 = select nnan nsz i1 %cmp1, double %x, double 1.0
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%cmp2 = fcmp olt double %sel1, 255.0
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%sel2 = select nnan nsz i1 %cmp2, double %sel1, double 255.0
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ret double %sel2
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}
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define i1 @test_fcmp_select_const_const_multiuse(double %x) {
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; CHECK-LABEL: @test_fcmp_select_const_const_multiuse(
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; CHECK-NEXT: [[CMP1:%.*]] = fcmp ord double [[X:%.*]], 0.000000e+00
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; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP1]], double 0xFFFFFFFFFFFFFFFF, double 0.000000e+00
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; CHECK-NEXT: call void @usef64(double [[SEL]])
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; CHECK-NEXT: [[CMP2:%.*]] = fcmp oeq double [[SEL]], 0.000000e+00
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; CHECK-NEXT: ret i1 [[CMP2]]
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;
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%cmp1 = fcmp ord double %x, 0.000000e+00
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%sel = select i1 %cmp1, double 0xFFFFFFFFFFFFFFFF, double 0.000000e+00
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call void @usef64(double %sel)
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%cmp2 = fcmp oeq double %sel, 0.000000e+00
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ret i1 %cmp2
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}
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define i1 @test_fcmp_select_const_const_unordered(double %x) {
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; CHECK-LABEL: @test_fcmp_select_const_const_unordered(
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; CHECK-NEXT: [[CMP1:%.*]] = fcmp ord double [[X:%.*]], 0.000000e+00
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; CHECK-NEXT: ret i1 [[CMP1]]
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;
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%cmp1 = fcmp uno double %x, 0.000000e+00
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%sel = select i1 %cmp1, double 0xFFFFFFFFFFFFFFFF, double 0.000000e+00
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%cmp2 = fcmp oeq double %sel, 0.000000e+00
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ret i1 %cmp2
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}
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define i1 @test_fcmp_select_var_const_unordered(double %x, double %y) {
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; CHECK-LABEL: @test_fcmp_select_var_const_unordered(
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; CHECK-NEXT: [[CMP1:%.*]] = fcmp ult double [[X:%.*]], 0x3E80000000000000
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; CHECK-NEXT: [[TMP1:%.*]] = fcmp ugt double [[Y:%.*]], 0x3E80000000000000
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; CHECK-NEXT: [[CMP2:%.*]] = select i1 [[CMP1]], i1 [[TMP1]], i1 false
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; CHECK-NEXT: ret i1 [[CMP2]]
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;
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%cmp1 = fcmp ult double %x, 0x3E80000000000000
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%sel = select i1 %cmp1, double %y, double 0.000000e+00
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%cmp2 = fcmp ugt double %sel, 0x3E80000000000000
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ret i1 %cmp2
270+
}

‎llvm/test/Transforms/InstCombine/select-select.ll

Lines changed: 3 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -18,11 +18,10 @@ define float @foo1(float %a) {
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define float @foo2(float %a) {
2020
; CHECK-LABEL: @foo2(
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; CHECK-NEXT: [[B:%.*]] = fcmp ogt float [[A:%.*]], 0.000000e+00
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; CHECK-NEXT: [[C:%.*]] = select i1 [[B]], float [[A]], float 0.000000e+00
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; CHECK-NEXT: [[B:%.*]] = fcmp ule float [[C:%.*]], 0.000000e+00
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; CHECK-NEXT: [[D:%.*]] = fcmp olt float [[C]], 1.000000e+00
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; CHECK-NEXT: [[E:%.*]] = select i1 [[B]], float [[A]], float 0.000000e+00
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; CHECK-NEXT: [[F:%.*]] = select i1 [[D]], float [[E]], float 1.000000e+00
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; CHECK-NEXT: [[E:%.*]] = select i1 [[D]], float [[C]], float 1.000000e+00
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; CHECK-NEXT: [[F:%.*]] = select i1 [[B]], float 0.000000e+00, float [[E]]
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; CHECK-NEXT: ret float [[F]]
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;
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%b = fcmp ogt float %a, 0.0

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