[llvm] r373851 - [InstCombine] fold fneg disguised as select+fmul (PR43497)
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Sun Oct 6 07:15:48 PDT 2019
Author: spatel
Date: Sun Oct 6 07:15:48 2019
New Revision: 373851
URL: http://llvm.org/viewvc/llvm-project?rev=373851&view=rev
Log:
[InstCombine] fold fneg disguised as select+fmul (PR43497)
Extends rL373230 and solves the motivating bug (although in a narrow way):
https://bugs.llvm.org/show_bug.cgi?id=43497
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
llvm/trunk/test/Transforms/InstCombine/fmul.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp?rev=373851&r1=373850&r2=373851&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp Sun Oct 6 07:15:48 2019
@@ -124,6 +124,50 @@ static Constant *getLogBase2(Type *Ty, C
return ConstantVector::get(Elts);
}
+// 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().
+static Value *foldMulSelectToNegate(BinaryOperator &I,
+ InstCombiner::BuilderTy &Builder) {
+ Value *Cond, *OtherOp;
+
+ // mul (select Cond, 1, -1), OtherOp --> select Cond, OtherOp, -OtherOp
+ // mul OtherOp, (select Cond, 1, -1) --> select Cond, OtherOp, -OtherOp
+ if (match(&I, m_c_Mul(m_OneUse(m_Select(m_Value(Cond), m_One(), m_AllOnes())),
+ m_Value(OtherOp))))
+ return Builder.CreateSelect(Cond, OtherOp, Builder.CreateNeg(OtherOp));
+
+ // mul (select Cond, -1, 1), OtherOp --> select Cond, -OtherOp, OtherOp
+ // mul OtherOp, (select Cond, -1, 1) --> select Cond, -OtherOp, OtherOp
+ if (match(&I, m_c_Mul(m_OneUse(m_Select(m_Value(Cond), m_AllOnes(), m_One())),
+ m_Value(OtherOp))))
+ return Builder.CreateSelect(Cond, Builder.CreateNeg(OtherOp), OtherOp);
+
+ // fmul (select Cond, 1.0, -1.0), OtherOp --> select Cond, OtherOp, -OtherOp
+ // fmul OtherOp, (select Cond, 1.0, -1.0) --> select Cond, OtherOp, -OtherOp
+ if (match(&I, m_c_FMul(m_OneUse(m_Select(m_Value(Cond), m_SpecificFP(1.0),
+ m_SpecificFP(-1.0))),
+ m_Value(OtherOp)))) {
+ IRBuilder<>::FastMathFlagGuard FMFGuard(Builder);
+ Builder.setFastMathFlags(I.getFastMathFlags());
+ return Builder.CreateSelect(Cond, OtherOp, Builder.CreateFNeg(OtherOp));
+ }
+
+ // fmul (select Cond, -1.0, 1.0), OtherOp --> select Cond, -OtherOp, OtherOp
+ // fmul OtherOp, (select Cond, -1.0, 1.0) --> select Cond, -OtherOp, OtherOp
+ if (match(&I, m_c_FMul(m_OneUse(m_Select(m_Value(Cond), m_SpecificFP(-1.0),
+ m_SpecificFP(1.0))),
+ m_Value(OtherOp)))) {
+ IRBuilder<>::FastMathFlagGuard FMFGuard(Builder);
+ Builder.setFastMathFlags(I.getFastMathFlags());
+ return Builder.CreateSelect(Cond, Builder.CreateFNeg(OtherOp), OtherOp);
+ }
+
+ return nullptr;
+}
+
Instruction *InstCombiner::visitMul(BinaryOperator &I) {
if (Value *V = SimplifyMulInst(I.getOperand(0), I.getOperand(1),
SQ.getWithInstruction(&I)))
@@ -213,24 +257,8 @@ Instruction *InstCombiner::visitMul(Bina
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);
+ if (Value *FoldedMul = foldMulSelectToNegate(I, Builder))
+ return replaceInstUsesWith(I, FoldedMul);
// Simplify mul instructions with a constant RHS.
if (isa<Constant>(Op1)) {
@@ -377,6 +405,9 @@ Instruction *InstCombiner::visitFMul(Bin
if (Instruction *FoldedMul = foldBinOpIntoSelectOrPhi(I))
return FoldedMul;
+ if (Value *FoldedMul = foldMulSelectToNegate(I, Builder))
+ return replaceInstUsesWith(I, FoldedMul);
+
// X * -1.0 --> -X
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
if (match(Op1, m_SpecificFP(-1.0)))
Modified: llvm/trunk/test/Transforms/InstCombine/fmul.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/fmul.ll?rev=373851&r1=373850&r2=373851&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/fmul.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/fmul.ll Sun Oct 6 07:15:48 2019
@@ -994,9 +994,9 @@ define double @fmul_negated_constant_exp
define float @negate_if_true(float %x, i1 %cond) {
; CHECK-LABEL: @negate_if_true(
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], float -1.000000e+00, float 1.000000e+00
-; CHECK-NEXT: [[R:%.*]] = fmul float [[SEL]], [[X:%.*]]
-; CHECK-NEXT: ret float [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = fsub float -0.000000e+00, [[X:%.*]]
+; CHECK-NEXT: [[TMP2:%.*]] = select i1 [[COND:%.*]], float [[TMP1]], float [[X]]
+; CHECK-NEXT: ret float [[TMP2]]
;
%sel = select i1 %cond, float -1.0, float 1.0
%r = fmul float %sel, %x
@@ -1005,9 +1005,9 @@ define float @negate_if_true(float %x, i
define float @negate_if_false(float %x, i1 %cond) {
; CHECK-LABEL: @negate_if_false(
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], float 1.000000e+00, float -1.000000e+00
-; CHECK-NEXT: [[R:%.*]] = fmul arcp float [[SEL]], [[X:%.*]]
-; CHECK-NEXT: ret float [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = fsub arcp float -0.000000e+00, [[X:%.*]]
+; CHECK-NEXT: [[TMP2:%.*]] = select arcp i1 [[COND:%.*]], float [[X]], float [[TMP1]]
+; CHECK-NEXT: ret float [[TMP2]]
;
%sel = select i1 %cond, float 1.0, float -1.0
%r = fmul arcp float %sel, %x
@@ -1017,9 +1017,9 @@ define float @negate_if_false(float %x,
define <2 x double> @negate_if_true_commute(<2 x double> %px, i1 %cond) {
; CHECK-LABEL: @negate_if_true_commute(
; CHECK-NEXT: [[X:%.*]] = fdiv <2 x double> <double 4.200000e+01, double 4.200000e+01>, [[PX:%.*]]
-; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], <2 x double> <double -1.000000e+00, double -1.000000e+00>, <2 x double> <double 1.000000e+00, double 1.000000e+00>
-; CHECK-NEXT: [[R:%.*]] = fmul ninf <2 x double> [[X]], [[SEL]]
-; CHECK-NEXT: ret <2 x double> [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = fsub ninf <2 x double> <double -0.000000e+00, double -0.000000e+00>, [[X]]
+; CHECK-NEXT: [[TMP2:%.*]] = select ninf i1 [[COND:%.*]], <2 x double> [[TMP1]], <2 x double> [[X]]
+; CHECK-NEXT: ret <2 x double> [[TMP2]]
;
%x = fdiv <2 x double> <double 42.0, double 42.0>, %px ; thwart complexity-based canonicalization
%sel = select i1 %cond, <2 x double> <double -1.0, double -1.0>, <2 x double> <double 1.0, double 1.0>
@@ -1030,9 +1030,9 @@ define <2 x double> @negate_if_true_comm
define <2 x double> @negate_if_false_commute(<2 x double> %px, <2 x i1> %cond) {
; CHECK-LABEL: @negate_if_false_commute(
; CHECK-NEXT: [[X:%.*]] = fdiv <2 x double> <double 4.200000e+01, double 5.100000e+00>, [[PX:%.*]]
-; CHECK-NEXT: [[SEL:%.*]] = select <2 x i1> [[COND:%.*]], <2 x double> <double 1.000000e+00, double 1.000000e+00>, <2 x double> <double -1.000000e+00, double -1.000000e+00>
-; CHECK-NEXT: [[R:%.*]] = fmul <2 x double> [[X]], [[SEL]]
-; CHECK-NEXT: ret <2 x double> [[R]]
+; CHECK-NEXT: [[TMP1:%.*]] = fsub <2 x double> <double -0.000000e+00, double -0.000000e+00>, [[X]]
+; CHECK-NEXT: [[TMP2:%.*]] = select <2 x i1> [[COND:%.*]], <2 x double> [[X]], <2 x double> [[TMP1]]
+; CHECK-NEXT: ret <2 x double> [[TMP2]]
;
%x = fdiv <2 x double> <double 42.0, double 5.1>, %px ; thwart complexity-based canonicalization
%sel = select <2 x i1> %cond, <2 x double> <double 1.0, double 1.0>, <2 x double> <double -1.0, double -1.0>
@@ -1040,6 +1040,8 @@ define <2 x double> @negate_if_false_com
ret <2 x double> %r
}
+; Negative test
+
define float @negate_if_true_extra_use(float %x, i1 %cond) {
; CHECK-LABEL: @negate_if_true_extra_use(
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[COND:%.*]], float -1.000000e+00, float 1.000000e+00
@@ -1053,6 +1055,8 @@ define float @negate_if_true_extra_use(f
ret float %r
}
+; Negative test
+
define <2 x double> @negate_if_true_wrong_constant(<2 x double> %px, i1 %cond) {
; CHECK-LABEL: @negate_if_true_wrong_constant(
; CHECK-NEXT: [[X:%.*]] = fdiv <2 x double> <double 4.200000e+01, double 4.200000e+01>, [[PX:%.*]]
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