[InstCombine] Add visitFNeg(...) visitor for unary Fneg

Also, break out a helper function, namely foldFNegIntoConstant(...), which performs transforms common between visitFNeg(...) and visitFSub(...).

Differential Revision: https://reviews.llvm.org/D61693

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@361188 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/IR/InstrTypes.h b/include/llvm/IR/InstrTypes.h
index fbf50ac475f8b664f3d0c88ef201bda4eee36a73..a595707f3a61427e88ea2dcf28957672e8921f40 100644 (file)
--- a/include/llvm/IR/InstrTypes.h
+++ b/include/llvm/IR/InstrTypes.h
@@ -225,39 +225,39 @@ public:
 
   static BinaryOperator *CreateWithCopiedFlags(BinaryOps Opc,
                                                Value *V1, Value *V2,
-                                               BinaryOperator *CopyBO,
+                                               Instruction *CopyO,
                                                const Twine &Name = "") {
     BinaryOperator *BO = Create(Opc, V1, V2, Name);
-    BO->copyIRFlags(CopyBO);
+    BO->copyIRFlags(CopyO);
     return BO;
   }
 
   static BinaryOperator *CreateFAddFMF(Value *V1, Value *V2,
-                                       BinaryOperator *FMFSource,
+                                       Instruction *FMFSource,
                                        const Twine &Name = "") {
     return CreateWithCopiedFlags(Instruction::FAdd, V1, V2, FMFSource, Name);
   }
   static BinaryOperator *CreateFSubFMF(Value *V1, Value *V2,
-                                       BinaryOperator *FMFSource,
+                                       Instruction *FMFSource,
                                        const Twine &Name = "") {
     return CreateWithCopiedFlags(Instruction::FSub, V1, V2, FMFSource, Name);
   }
   static BinaryOperator *CreateFMulFMF(Value *V1, Value *V2,
-                                       BinaryOperator *FMFSource,
+                                       Instruction *FMFSource,
                                        const Twine &Name = "") {
     return CreateWithCopiedFlags(Instruction::FMul, V1, V2, FMFSource, Name);
   }
   static BinaryOperator *CreateFDivFMF(Value *V1, Value *V2,
-                                       BinaryOperator *FMFSource,
+                                       Instruction *FMFSource,
                                        const Twine &Name = "") {
     return CreateWithCopiedFlags(Instruction::FDiv, V1, V2, FMFSource, Name);
   }
   static BinaryOperator *CreateFRemFMF(Value *V1, Value *V2,
-                                       BinaryOperator *FMFSource,
+                                       Instruction *FMFSource,
                                        const Twine &Name = "") {
     return CreateWithCopiedFlags(Instruction::FRem, V1, V2, FMFSource, Name);
   }
-  static BinaryOperator *CreateFNegFMF(Value *Op, BinaryOperator *FMFSource,
+  static BinaryOperator *CreateFNegFMF(Value *Op, Instruction *FMFSource,
                                        const Twine &Name = "") {
     Value *Zero = ConstantFP::getNegativeZero(Op->getType());
     return CreateWithCopiedFlags(Instruction::FSub, Zero, Op, FMFSource);

diff --git a/lib/Transforms/InstCombine/InstCombineAddSub.cpp b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
index 5f5a94e4b256b6b030066c65c4fc61849295dda5..421d49fdcb7076b935ab995d2a838d39db76a3ff 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineAddSub.cpp
+++ b/lib/Transforms/InstCombine/InstCombineAddSub.cpp
@@ -1821,15 +1821,38 @@ Instruction *InstCombiner::visitSub(BinaryOperator &I) {
   return Changed ? &I : nullptr;
 }
 
+/// This eliminates floating-point negation in either 'fneg(X)' or
+/// 'fsub(-0.0, X)' form by combining into a constant operand.
+static Instruction *foldFNegIntoConstant(Instruction &I) {
+  Value *X;
+  Constant *C;
+
+  // Fold negation into constant operand. This is limited with one-use because
+  // fneg is assumed better for analysis and cheaper in codegen than fmul/fdiv.
+  // -(X * C) --> X * (-C)
+  if (match(&I, m_FNeg(m_OneUse(m_FMul(m_Value(X), m_Constant(C))))))
+    return BinaryOperator::CreateFMulFMF(X, ConstantExpr::getFNeg(C), &I);
+  // -(X / C) --> X / (-C)
+  if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Value(X), m_Constant(C))))))
+    return BinaryOperator::CreateFDivFMF(X, ConstantExpr::getFNeg(C), &I);
+  // -(C / X) --> (-C) / X
+  if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Constant(C), m_Value(X))))))
+    return BinaryOperator::CreateFDivFMF(ConstantExpr::getFNeg(C), X, &I);
+
+  return nullptr;
+}
+
 Instruction *InstCombiner::visitFNeg(UnaryOperator &I) {
   if (Value *V = SimplifyFNegInst(I.getOperand(0), I.getFastMathFlags(),
                                   SQ.getWithInstruction(&I)))
     return replaceInstUsesWith(I, V);
 
+  if (Instruction *X = foldFNegIntoConstant(I))
+    return X;
+
   return nullptr;
 }
 
-
 Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
   if (Value *V = SimplifyFSubInst(I.getOperand(0), I.getOperand(1),
                                   I.getFastMathFlags(),
@@ -1845,21 +1868,12 @@ Instruction *InstCombiner::visitFSub(BinaryOperator &I) {
   if (I.hasNoSignedZeros() && match(Op0, m_PosZeroFP()))
     return BinaryOperator::CreateFNegFMF(Op1, &I);
 
+  if (Instruction *X = foldFNegIntoConstant(I))
+    return X;
+
   Value *X, *Y;
   Constant *C;
 
-  // Fold negation into constant operand. This is limited with one-use because
-  // fneg is assumed better for analysis and cheaper in codegen than fmul/fdiv.
-  // -(X * C) --> X * (-C)
-  if (match(&I, m_FNeg(m_OneUse(m_FMul(m_Value(X), m_Constant(C))))))
-    return BinaryOperator::CreateFMulFMF(X, ConstantExpr::getFNeg(C), &I);
-  // -(X / C) --> X / (-C)
-  if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Value(X), m_Constant(C))))))
-    return BinaryOperator::CreateFDivFMF(X, ConstantExpr::getFNeg(C), &I);
-  // -(C / X) --> (-C) / X
-  if (match(&I, m_FNeg(m_OneUse(m_FDiv(m_Constant(C), m_Value(X))))))
-    return BinaryOperator::CreateFDivFMF(ConstantExpr::getFNeg(C), X, &I);
-
   // If Op0 is not -0.0 or we can ignore -0.0: Z - (X - Y) --> Z + (Y - X)
   // Canonicalize to fadd to make analysis easier.
   // This can also help codegen because fadd is commutative.

diff --git a/test/Transforms/InstCombine/fneg.ll b/test/Transforms/InstCombine/fneg.ll
index 2fdb1947912e2359ffa7b275672947c80d9ddf79..bb701ba4895360944a9e1bd54aa5648fa3f3f73a 100644 (file)
--- a/test/Transforms/InstCombine/fneg.ll
+++ b/test/Transforms/InstCombine/fneg.ll
@@ -27,8 +27,7 @@ define float @fmul_fsub(float %x) {
 
 define float @fmul_fneg(float %x) {
 ; CHECK-LABEL: @fmul_fneg(
-; CHECK-NEXT:    [[M:%.*]] = fmul float [[X:%.*]], 4.200000e+01
-; CHECK-NEXT:    [[R:%.*]] = fneg float [[M]]
+; CHECK-NEXT:    [[R:%.*]] = fmul float [[X:%.*]], -4.200000e+01
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %m = fmul float %x, 42.0
@@ -50,8 +49,7 @@ define float @fmul_fsub_fmf(float %x) {
 
 define float @fmul_fneg_fmf(float %x) {
 ; CHECK-LABEL: @fmul_fneg_fmf(
-; CHECK-NEXT:    [[M:%.*]] = fmul float [[X:%.*]], 4.200000e+01
-; CHECK-NEXT:    [[R:%.*]] = fneg reassoc nsz float [[M]]
+; CHECK-NEXT:    [[R:%.*]] = fmul reassoc nsz float [[X:%.*]], -4.200000e+01
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %m = fmul float %x, 42.0
@@ -101,8 +99,7 @@ define <4 x double> @fmul_fsub_vec(<4 x double> %x) {
 
 define <4 x double> @fmul_fneg_vec(<4 x double> %x) {
 ; CHECK-LABEL: @fmul_fneg_vec(
-; CHECK-NEXT:    [[M:%.*]] = fmul <4 x double> [[X:%.*]], <double 4.200000e+01, double 0xFF80000000000000, double 0x7FF0000000000000, double undef>
-; CHECK-NEXT:    [[R:%.*]] = fneg <4 x double> [[M]]
+; CHECK-NEXT:    [[R:%.*]] = fmul <4 x double> [[X:%.*]], <double -4.200000e+01, double 0x7F80000000000000, double 0xFFF0000000000000, double undef>
 ; CHECK-NEXT:    ret <4 x double> [[R]]
 ;
   %m = fmul <4 x double> %x, <double 42.0, double 0x7FF80000000000000, double 0x7FF0000000000000, double undef>
@@ -124,8 +121,7 @@ define float @fdiv_op1_constant_fsub(float %x) {
 
 define float @fdiv_op1_constant_fneg(float %x) {
 ; CHECK-LABEL: @fdiv_op1_constant_fneg(
-; CHECK-NEXT:    [[D:%.*]] = fdiv float [[X:%.*]], -4.200000e+01
-; CHECK-NEXT:    [[R:%.*]] = fneg float [[D]]
+; CHECK-NEXT:    [[R:%.*]] = fdiv float [[X:%.*]], 4.200000e+01
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %d = fdiv float %x, -42.0
@@ -147,8 +143,7 @@ define float @fdiv_op1_constant_fsub_fmf(float %x) {
 
 define float @fdiv_op1_constant_fneg_fmf(float %x) {
 ; CHECK-LABEL: @fdiv_op1_constant_fneg_fmf(
-; CHECK-NEXT:    [[D:%.*]] = fdiv float [[X:%.*]], -4.200000e+01
-; CHECK-NEXT:    [[R:%.*]] = fneg nnan float [[D]]
+; CHECK-NEXT:    [[R:%.*]] = fdiv nnan float [[X:%.*]], 4.200000e+01
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %d = fdiv float %x, -42.0
@@ -198,8 +193,7 @@ define <4 x double> @fdiv_op1_constant_fsub_vec(<4 x double> %x) {
 
 define <4 x double> @fdiv_op1_constant_fneg_vec(<4 x double> %x) {
 ; CHECK-LABEL: @fdiv_op1_constant_fneg_vec(
-; CHECK-NEXT:    [[D:%.*]] = fdiv <4 x double> [[X:%.*]], <double -4.200000e+01, double 0xFFF800000ABCD000, double 0xFFF0000000000000, double undef>
-; CHECK-NEXT:    [[R:%.*]] = fneg <4 x double> [[D]]
+; CHECK-NEXT:    [[R:%.*]] = fdiv <4 x double> [[X:%.*]], <double 4.200000e+01, double 0x7FF800000ABCD000, double 0x7FF0000000000000, double undef>
 ; CHECK-NEXT:    ret <4 x double> [[R]]
 ;
   %d = fdiv <4 x double> %x, <double -42.0, double 0xFFF800000ABCD000, double 0xFFF0000000000000, double undef>
@@ -221,8 +215,7 @@ define float @fdiv_op0_constant_fsub(float %x) {
 
 define float @fdiv_op0_constant_fneg(float %x) {
 ; CHECK-LABEL: @fdiv_op0_constant_fneg(
-; CHECK-NEXT:    [[D:%.*]] = fdiv float 4.200000e+01, [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = fneg float [[D]]
+; CHECK-NEXT:    [[R:%.*]] = fdiv float -4.200000e+01, [[X:%.*]]
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %d = fdiv float 42.0, %x
@@ -244,8 +237,7 @@ define float @fdiv_op0_constant_fsub_fmf(float %x) {
 
 define float @fdiv_op0_constant_fneg_fmf(float %x) {
 ; CHECK-LABEL: @fdiv_op0_constant_fneg_fmf(
-; CHECK-NEXT:    [[D:%.*]] = fdiv float 4.200000e+01, [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = fneg fast float [[D]]
+; CHECK-NEXT:    [[R:%.*]] = fdiv fast float -4.200000e+01, [[X:%.*]]
 ; CHECK-NEXT:    ret float [[R]]
 ;
   %d = fdiv float 42.0, %x
@@ -295,8 +287,7 @@ define <4 x double> @fdiv_op0_constant_fsub_vec(<4 x double> %x) {
 
 define <4 x double> @fdiv_op0_constant_fneg_vec(<4 x double> %x) {
 ; CHECK-LABEL: @fdiv_op0_constant_fneg_vec(
-; CHECK-NEXT:    [[D:%.*]] = fdiv <4 x double> <double -4.200000e+01, double 0xFF80000000000000, double 0xFFF0000000000000, double undef>, [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = fneg <4 x double> [[D]]
+; CHECK-NEXT:    [[R:%.*]] = fdiv <4 x double> <double 4.200000e+01, double 0x7F80000000000000, double 0x7FF0000000000000, double undef>, [[X:%.*]]
 ; CHECK-NEXT:    ret <4 x double> [[R]]
 ;
   %d = fdiv <4 x double> <double -42.0, double 0x7FF80000000000000, double 0xFFF0000000000000, double undef>, %x