From e7c94ef1debe790ab90833cf72e21b584651db16 Mon Sep 17 00:00:00 2001 From: Sanjay Patel Date: Sun, 4 Nov 2018 14:28:48 +0000 Subject: [PATCH] [ValueTracking] determine sign of 0.0 from select when matching min/max FP In PR39475: https://bugs.llvm.org/show_bug.cgi?id=39475 ..we may fail to recognize/simplify fabs() in some cases because we do not canonicalize fcmp with a -0.0 operand. Adding that canonicalization can cause regressions on min/max FP tests, so that's this patch: for the purpose of determining whether something is min/max, let the value returned by the select determine how we treat a 0.0 operand in the fcmp. This patch doesn't actually change the -0.0 to +0.0. It just changes the analysis, so we don't fail to recognize equivalent min/max patterns that only differ in the signbit of 0.0. Differential Revision: https://reviews.llvm.org/D54001 llvm-svn: 346097 --- llvm/lib/Analysis/ValueTracking.cpp | 21 +++++ llvm/test/Transforms/InstCombine/minmax-fp.ll | 38 ++++----- llvm/unittests/Analysis/ValueTrackingTest.cpp | 84 ++++++++++++------- 3 files changed, 89 insertions(+), 54 deletions(-) diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 6e08272c64e7..ed17441d1e40 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -4760,6 +4760,27 @@ static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred, Value *TrueVal, Value *FalseVal, Value *&LHS, Value *&RHS, unsigned Depth) { + if (CmpInst::isFPPredicate(Pred)) { + // IEEE-754 ignores the sign of 0.0 in comparisons. So if the select has one + // 0.0 operand, set the compare's 0.0 operands to that same value for the + // purpose of identifying min/max. Disregard vector constants with undefined + // elements because those can not be back-propagated for analysis. + Value *OutputZeroVal = nullptr; + if (match(TrueVal, m_AnyZeroFP()) && !match(FalseVal, m_AnyZeroFP()) && + !cast(TrueVal)->containsUndefElement()) + OutputZeroVal = TrueVal; + else if (match(FalseVal, m_AnyZeroFP()) && !match(TrueVal, m_AnyZeroFP()) && + !cast(FalseVal)->containsUndefElement()) + OutputZeroVal = FalseVal; + + if (OutputZeroVal) { + if (match(CmpLHS, m_AnyZeroFP())) + CmpLHS = OutputZeroVal; + if (match(CmpRHS, m_AnyZeroFP())) + CmpRHS = OutputZeroVal; + } + } + LHS = CmpLHS; RHS = CmpRHS; diff --git a/llvm/test/Transforms/InstCombine/minmax-fp.ll b/llvm/test/Transforms/InstCombine/minmax-fp.ll index 292e50eb1f9c..7bf8f57d4e86 100644 --- a/llvm/test/Transforms/InstCombine/minmax-fp.ll +++ b/llvm/test/Transforms/InstCombine/minmax-fp.ll @@ -57,16 +57,15 @@ define double @t5(float %a) { ret double %3 } -; TODO: -; From IEEE754: "Comparisons shall ignore the sign of zero (so +0 = −0)." +; From IEEE754: "Comparisons shall ignore the sign of zero (so +0 = -0)." ; So the compare constant may be treated as +0.0, and we sink the fpext. define double @t6(float %a) { ; CHECK-LABEL: @t6( -; CHECK-NEXT: [[TMP1:%.*]] = fcmp ult float [[A:%.*]], -0.000000e+00 -; CHECK-NEXT: [[TMP2:%.*]] = fpext float [[A]] to double -; CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP1]], double [[TMP2]], double 0.000000e+00 -; CHECK-NEXT: ret double [[TMP3]] +; CHECK-NEXT: [[DOTINV:%.*]] = fcmp oge float [[A:%.*]], 0.000000e+00 +; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[DOTINV]], float 0.000000e+00, float [[A]] +; CHECK-NEXT: [[TMP2:%.*]] = fpext float [[TMP1]] to double +; CHECK-NEXT: ret double [[TMP2]] ; %1 = fcmp ult float %a, -0.0 %2 = fpext float %a to double @@ -74,16 +73,15 @@ define double @t6(float %a) { ret double %3 } -; TODO: -; From IEEE754: "Comparisons shall ignore the sign of zero (so +0 = −0)." +; From IEEE754: "Comparisons shall ignore the sign of zero (so +0 = -0)." ; So the compare constant may be treated as -0.0, and we sink the fpext. define double @t7(float %a) { ; CHECK-LABEL: @t7( -; CHECK-NEXT: [[TMP1:%.*]] = fcmp ult float [[A:%.*]], 0.000000e+00 -; CHECK-NEXT: [[TMP2:%.*]] = fpext float [[A]] to double -; CHECK-NEXT: [[TMP3:%.*]] = select i1 [[TMP1]], double [[TMP2]], double -0.000000e+00 -; CHECK-NEXT: ret double [[TMP3]] +; CHECK-NEXT: [[DOTINV:%.*]] = fcmp oge float [[A:%.*]], -0.000000e+00 +; CHECK-NEXT: [[TMP1:%.*]] = select i1 [[DOTINV]], float -0.000000e+00, float [[A]] +; CHECK-NEXT: [[TMP2:%.*]] = fpext float [[TMP1]] to double +; CHECK-NEXT: ret double [[TMP2]] ; %1 = fcmp ult float %a, 0.0 %2 = fpext float %a to double @@ -91,15 +89,12 @@ define double @t7(float %a) { ret double %3 } -; TODO: ; min(min(x, 0.0), 0.0) --> min(x, 0.0) define float @fmin_fmin_zero_mismatch(float %x) { ; CHECK-LABEL: @fmin_fmin_zero_mismatch( -; CHECK-NEXT: [[CMP1:%.*]] = fcmp olt float [[X:%.*]], -0.000000e+00 -; CHECK-NEXT: [[MIN1:%.*]] = select i1 [[CMP1]], float [[X]], float 0.000000e+00 -; CHECK-NEXT: [[CMP2:%.*]] = fcmp olt float [[MIN1]], 0.000000e+00 -; CHECK-NEXT: [[MIN2:%.*]] = select i1 [[CMP2]], float [[MIN1]], float 0.000000e+00 +; CHECK-NEXT: [[TMP1:%.*]] = fcmp olt float [[X:%.*]], 0.000000e+00 +; CHECK-NEXT: [[MIN2:%.*]] = select i1 [[TMP1]], float [[X]], float 0.000000e+00 ; CHECK-NEXT: ret float [[MIN2]] ; %cmp1 = fcmp olt float %x, -0.0 @@ -109,16 +104,13 @@ define float @fmin_fmin_zero_mismatch(float %x) { ret float %min2 } -; TODO: ; max(max(x, -0.0), -0.0) --> max(x, -0.0) define float @fmax_fmax_zero_mismatch(float %x) { ; CHECK-LABEL: @fmax_fmax_zero_mismatch( -; CHECK-NEXT: [[CMP1:%.*]] = fcmp ogt float [[X:%.*]], 0.000000e+00 -; CHECK-NEXT: [[MAX1:%.*]] = select i1 [[CMP1]], float [[X]], float -0.000000e+00 -; CHECK-NEXT: [[CMP2:%.*]] = fcmp olt float [[MAX1]], 0.000000e+00 -; CHECK-NEXT: [[MAX2:%.*]] = select i1 [[CMP2]], float -0.000000e+00, float [[MAX1]] -; CHECK-NEXT: ret float [[MAX2]] +; CHECK-NEXT: [[TMP1:%.*]] = fcmp ogt float [[X:%.*]], -0.000000e+00 +; CHECK-NEXT: [[MAX11:%.*]] = select i1 [[TMP1]], float [[X]], float -0.000000e+00 +; CHECK-NEXT: ret float [[MAX11]] ; %cmp1 = fcmp ogt float %x, 0.0 %max1 = select i1 %cmp1, float %x, float -0.0 diff --git a/llvm/unittests/Analysis/ValueTrackingTest.cpp b/llvm/unittests/Analysis/ValueTrackingTest.cpp index b13948adad71..c4adde4abe34 100644 --- a/llvm/unittests/Analysis/ValueTrackingTest.cpp +++ b/llvm/unittests/Analysis/ValueTrackingTest.cpp @@ -156,8 +156,8 @@ TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero1) { " %A = select i1 %1, float 0.0, float %a\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMINNUM, SPNB_RETURNS_NAN, true}); } TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero2) { @@ -167,8 +167,8 @@ TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero2) { " %A = select i1 %1, float 0.0, float %a\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMINNUM, SPNB_RETURNS_NAN, false}); } TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero3) { @@ -178,8 +178,8 @@ TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero3) { " %A = select i1 %1, float -0.0, float %a\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMINNUM, SPNB_RETURNS_NAN, true}); } TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero4) { @@ -189,8 +189,8 @@ TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero4) { " %A = select i1 %1, float -0.0, float %a\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMINNUM, SPNB_RETURNS_NAN, false}); } TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero5) { @@ -200,8 +200,8 @@ TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero5) { " %A = select i1 %1, float %a, float 0.0\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMINNUM, SPNB_RETURNS_OTHER, false}); } TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero6) { @@ -211,8 +211,8 @@ TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero6) { " %A = select i1 %1, float %a, float 0.0\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMINNUM, SPNB_RETURNS_OTHER, true}); } TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero7) { @@ -222,8 +222,8 @@ TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero7) { " %A = select i1 %1, float %a, float -0.0\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMINNUM, SPNB_RETURNS_OTHER, false}); } TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero8) { @@ -233,8 +233,8 @@ TEST_F(MatchSelectPatternTest, FMinMismatchConstantZero8) { " %A = select i1 %1, float %a, float -0.0\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMINNUM, SPNB_RETURNS_OTHER, true}); } TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero1) { @@ -244,8 +244,8 @@ TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero1) { " %A = select i1 %1, float 0.0, float %a\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMAXNUM, SPNB_RETURNS_NAN, true}); } TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero2) { @@ -255,8 +255,8 @@ TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero2) { " %A = select i1 %1, float 0.0, float %a\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMAXNUM, SPNB_RETURNS_NAN, false}); } TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero3) { @@ -266,8 +266,8 @@ TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero3) { " %A = select i1 %1, float -0.0, float %a\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMAXNUM, SPNB_RETURNS_NAN, true}); } TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero4) { @@ -277,8 +277,8 @@ TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero4) { " %A = select i1 %1, float -0.0, float %a\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMAXNUM, SPNB_RETURNS_NAN, false}); } TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero5) { @@ -288,8 +288,8 @@ TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero5) { " %A = select i1 %1, float %a, float 0.0\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMAXNUM, SPNB_RETURNS_OTHER, false}); } TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero6) { @@ -299,8 +299,8 @@ TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero6) { " %A = select i1 %1, float %a, float 0.0\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMAXNUM, SPNB_RETURNS_OTHER, true}); } TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero7) { @@ -310,8 +310,8 @@ TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero7) { " %A = select i1 %1, float %a, float -0.0\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. - expectPattern({SPF_UNKNOWN, SPNB_NA, false}); + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMAXNUM, SPNB_RETURNS_OTHER, false}); } TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero8) { @@ -321,7 +321,29 @@ TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZero8) { " %A = select i1 %1, float %a, float -0.0\n" " ret float %A\n" "}\n"); - // FIXME: The sign of zero doesn't matter in fcmp. + // The sign of zero doesn't matter in fcmp. + expectPattern({SPF_FMAXNUM, SPNB_RETURNS_OTHER, true}); +} + +TEST_F(MatchSelectPatternTest, FMinMismatchConstantZeroVecUndef) { + parseAssembly( + "define <2 x float> @test(<2 x float> %a) {\n" + " %1 = fcmp ogt <2 x float> %a, \n" + " %A = select <2 x i1> %1, <2 x float> , <2 x float> %a\n" + " ret <2 x float> %A\n" + "}\n"); + // An undef in a vector constant can not be back-propagated for this analysis. + expectPattern({SPF_UNKNOWN, SPNB_NA, false}); +} + +TEST_F(MatchSelectPatternTest, FMaxMismatchConstantZeroVecUndef) { + parseAssembly( + "define <2 x float> @test(<2 x float> %a) {\n" + " %1 = fcmp ogt <2 x float> %a, zeroinitializer\n" + " %A = select <2 x i1> %1, <2 x float> %a, <2 x float> \n" + " ret <2 x float> %A\n" + "}\n"); + // An undef in a vector constant can not be back-propagated for this analysis. expectPattern({SPF_UNKNOWN, SPNB_NA, false}); } -- 2.34.1