[NFC][DAGCombine] Adding three helper functions and change the getNegatedExpression to negateExpression

[steven.zhang]

Summary

This is a NFC patch for D77319. The idea is to hide the getNegatibleCost inside the getNegatedExpression() to have it return null if the cost is expensive, and add some helper function for easy to use. And rename the old getNegatedExpression to negateExpression to avoid the semantic conflict. In the latter patch, we will remove the getNegatibleCost and negateExpression.

[steven.zhang]

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

12714

This lines of code is a bit tricky, we can write it as

TargetLowering::NegatibleCost CostN0 =
    TargetLowering::NegatibleCost::Expensive;
TargetLowering::NegatibleCost CostN1 =
    TargetLowering::NegatibleCost::Expensive;
SDValue NegN0 =
    TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize, CostN0);
SDValue NegN1 =
    TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize, CostN1);
if (NegN0 && NegN1 &&
    (CostN0 == TargetLowering::NegatibleCost::Cheaper ||
     CostN1 == TargetLowering::NegatibleCost::Cheaper)) {
  return DAG.getNode(ISD::FMUL, DL, VT, NegN0, NegN1, Flags);
}

However, they are not semantics the same, as current implementation don't want to negate the expression if the cost of negate N0 and N1 are both neutral while the above implementation did. Technical speaking, it won't have bad impact as we don't change the FMUL if both are neutral. However, it changes the order of the node to combine, which change the PowerPC test llvm/test/CodeGen/PowerPC/qpx-recipest.ll we see in D77319 Maybe, we need another patch to change the semantics and PowerPC test.

[RKSimon]

llvm/include/llvm/CodeGen/TargetLowering.h

3547

Its annoying that we're introducing negateExpression that will then go away again in D77319 - is there anyway to avoid creating negateExpression?

[steven.zhang]

llvm/include/llvm/CodeGen/TargetLowering.h

3547

Old getNegatedExpression means always negate the expr and never fail. We are changing the sematics to allow it failing if return null. And we need both the old getNegatedExpression and new one in this nfc patch. So I have to rename it. The negateExpression is only called inside target lowering，and merged with getNegatibleCost into getNegatedExpression in D77319. I don't have good idea not to rename it. Do you have any idea ？

[steven.zhang]

Gentle ping ...

[RKSimon]

LGTM - cheers

llvm/include/llvm/CodeGen/TargetLowering.h

3547

No good ideas - hence my vague "its annoying" comment :-)

[steven.zhang]

llvm/include/llvm/CodeGen/TargetLowering.h

3547

Thank you for the review :)

[steven.zhang]

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

12714

I suddenly realize that, the change here is still not strict-NFC, because we change the DAG when trying to get the cheaper negated expression of N0, which will affect the N1. I will leave this part unchanged and do it in D77319.

[steven.zhang]

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

12714

Do it in D78347 I mean.

llvm/include/llvm/CodeGen/TargetLowering.h

public:
   /// Returns whether computing the negated form of the specified expression is
   /// more expensive, the same cost or cheaper.
   virtual NegatibleCost getNegatibleCost(SDValue Op, SelectionDAG &DAG,
                                          bool LegalOperations, bool ForCodeSize,
                                          unsigned Depth = 0) const;
 
   /// If getNegatibleCost returns Neutral/Cheaper, return the newly negated
   /// expression.
-  virtual SDValue getNegatedExpression(SDValue Op, SelectionDAG &DAG,
-                                       bool LegalOperations, bool ForCodeSize,
-                                       unsigned Depth = 0) const;
+  virtual SDValue negateExpression(SDValue Op, SelectionDAG &DAG, bool LegalOps,
+                                   bool OptForSize, unsigned Depth = 0) const;
+
+  /// Return the newly negated expression if the cost is not expensive and
+  /// set the cost in \p Cost to indicate that if it is cheaper or neutral to
+  /// do the negation.
+  SDValue getNegatedExpression(SDValue Op, SelectionDAG &DAG, bool LegalOps,
+                               bool OptForSize, NegatibleCost &Cost,
+                               unsigned Depth = 0) const {
+    Cost = getNegatibleCost(Op, DAG, LegalOps, OptForSize, Depth);
+    if (Cost != NegatibleCost::Expensive)
+      return negateExpression(Op, DAG, LegalOps, OptForSize, Depth);
+    return SDValue();
+  }
+
+  /// This is the helper function to return the newly negated expression only
+  /// when the cost is cheaper.
+  SDValue getCheaperNegatedExpression(SDValue Op, SelectionDAG &DAG,
+                                      bool LegalOps, bool OptForSize,
+                                      unsigned Depth = 0) const {
+    if (getNegatibleCost(Op, DAG, LegalOps, OptForSize, Depth) ==
+        NegatibleCost::Cheaper)
+      return negateExpression(Op, DAG, LegalOps, OptForSize, Depth);
+    return SDValue();
+  }
+
+  /// This is the helper function to return the newly negated expression if
+  /// the cost is not expensive.
+  SDValue getNegatedExpression(SDValue Op, SelectionDAG &DAG, bool LegalOps,
+                               bool OptForSize, unsigned Depth = 0) const {
+    NegatibleCost Cost = NegatibleCost::Expensive;
+    return getNegatedExpression(Op, DAG, LegalOps, OptForSize, Cost, Depth);
+  }
 
   //===--------------------------------------------------------------------===//
   // Lowering methods - These methods must be implemented by targets so that
   // the SelectionDAGBuilder code knows how to lower these.
   //
 
   /// This hook must be implemented to lower the incoming (formal) arguments,
   /// described by the Ins array, into the specified DAG. The implementation

llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp

SDValue DAGCombiner::visitFADD(SDNode *N) {
   if (N1C && N1C->isZero())
     if (N1C->isNegative() || Options.NoSignedZerosFPMath || Flags.hasNoSignedZeros())
       return N0;
 
   if (SDValue NewSel = foldBinOpIntoSelect(N))
     return NewSel;
 
   // fold (fadd A, (fneg B)) -> (fsub A, B)
-  if ((!LegalOperations || TLI.isOperationLegalOrCustom(ISD::FSUB, VT)) &&
-      TLI.getNegatibleCost(N1, DAG, LegalOperations, ForCodeSize) ==
-          TargetLowering::NegatibleCost::Cheaper)
-    return DAG.getNode(
-        ISD::FSUB, DL, VT, N0,
-        TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize), Flags);
+  if (!LegalOperations || TLI.isOperationLegalOrCustom(ISD::FSUB, VT))
+    if (SDValue NegN1 = TLI.getCheaperNegatedExpression(
+            N1, DAG, LegalOperations, ForCodeSize))
+      return DAG.getNode(ISD::FSUB, DL, VT, N0, NegN1, Flags);
 
   // fold (fadd (fneg A), B) -> (fsub B, A)
-  if ((!LegalOperations || TLI.isOperationLegalOrCustom(ISD::FSUB, VT)) &&
-      TLI.getNegatibleCost(N0, DAG, LegalOperations, ForCodeSize) ==
-          TargetLowering::NegatibleCost::Cheaper)
-    return DAG.getNode(
-        ISD::FSUB, DL, VT, N1,
-        TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize), Flags);
+  if (!LegalOperations || TLI.isOperationLegalOrCustom(ISD::FSUB, VT))
+    if (SDValue NegN0 = TLI.getCheaperNegatedExpression(
+            N0, DAG, LegalOperations, ForCodeSize))
+      return DAG.getNode(ISD::FSUB, DL, VT, N1, NegN0, Flags);
 
   auto isFMulNegTwo = [](SDValue FMul) {
     if (!FMul.hasOneUse() || FMul.getOpcode() != ISD::FMUL)
       return false;
     auto *C = isConstOrConstSplatFP(FMul.getOperand(1), true);
     return C && C->isExactlyValue(-2.0);
   };
 
SDValue DAGCombiner::visitFSUB(SDNode *N) {
   // (fsub -0.0, N1) -> -N1
   // NOTE: It is safe to transform an FSUB(-0.0,X) into an FNEG(X), since the
   //       FSUB does not specify the sign bit of a NaN. Also note that for
   //       the same reason, the inverse transform is not safe, unless fast math
   //       flags are in play.
   if (N0CFP && N0CFP->isZero()) {
     if (N0CFP->isNegative() ||
         (Options.NoSignedZerosFPMath || Flags.hasNoSignedZeros())) {
-      if (TLI.getNegatibleCost(N1, DAG, LegalOperations, ForCodeSize) !=
-          TargetLowering::NegatibleCost::Expensive)
-        return TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize);
+      if (SDValue NegN1 =
+              TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize))
+        return NegN1;
       if (!LegalOperations || TLI.isOperationLegal(ISD::FNEG, VT))
         return DAG.getNode(ISD::FNEG, DL, VT, N1, Flags);
     }
   }
 
   if (((Options.UnsafeFPMath && Options.NoSignedZerosFPMath) ||
        (Flags.hasAllowReassociation() && Flags.hasNoSignedZeros())) &&
       N1.getOpcode() == ISD::FADD) {
     // X - (X + Y) -> -Y
     if (N0 == N1->getOperand(0))
       return DAG.getNode(ISD::FNEG, DL, VT, N1->getOperand(1), Flags);
     // X - (Y + X) -> -Y
     if (N0 == N1->getOperand(1))
       return DAG.getNode(ISD::FNEG, DL, VT, N1->getOperand(0), Flags);
   }
 
   // fold (fsub A, (fneg B)) -> (fadd A, B)
-  if (TLI.getNegatibleCost(N1, DAG, LegalOperations, ForCodeSize) !=
-      TargetLowering::NegatibleCost::Expensive)
-    return DAG.getNode(
-        ISD::FADD, DL, VT, N0,
-        TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize), Flags);
+  if (SDValue NegN1 =
+          TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize))
+    return DAG.getNode(ISD::FADD, DL, VT, N0, NegN1, Flags);
 
   // FSUB -> FMA combines:
   if (SDValue Fused = visitFSUBForFMACombine(N)) {
     AddToWorklist(Fused.getNode());
     return Fused;
   }
 
   return SDValue();
SDValue DAGCombiner::visitFMUL(SDNode *N) {
 
   // fold (fmul X, -1.0) -> (fneg X)
   if (N1CFP && N1CFP->isExactlyValue(-1.0))
     if (!LegalOperations || TLI.isOperationLegal(ISD::FNEG, VT))
       return DAG.getNode(ISD::FNEG, DL, VT, N0);
 
   // -N0 * -N1 --> N0 * N1
   if (isCheaperToUseNegatedFPOps(N0, N1)) {
-    SDValue NegN0 =
-        TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize);
-    SDValue NegN1 =
-        TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize);
+    SDValue NegN0 = TLI.negateExpression(N0, DAG, LegalOperations, ForCodeSize);
+    SDValue NegN1 = TLI.negateExpression(N1, DAG, LegalOperations, ForCodeSize);
     return DAG.getNode(ISD::FMUL, DL, VT, NegN0, NegN1, Flags);
   }
 
   // fold (fmul X, (select (fcmp X > 0.0), -1.0, 1.0)) -> (fneg (fabs X))
   // fold (fmul X, (select (fcmp X > 0.0), 1.0, -1.0)) -> (fabs X)
   if (Flags.hasNoNaNs() && Flags.hasNoSignedZeros() &&
       (N0.getOpcode() == ISD::SELECT || N1.getOpcode() == ISD::SELECT) &&
       TLI.isOperationLegal(ISD::FABS, VT)) {
SDValue DAGCombiner::visitFMA(SDNode *N) {
   if (isa<ConstantFPSDNode>(N0) &&
       isa<ConstantFPSDNode>(N1) &&
       isa<ConstantFPSDNode>(N2)) {
     return DAG.getNode(ISD::FMA, DL, VT, N0, N1, N2);
   }
 
   // (-N0 * -N1) + N2 --> (N0 * N1) + N2
   if (isCheaperToUseNegatedFPOps(N0, N1)) {
-    SDValue NegN0 =
-        TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize);
-    SDValue NegN1 =
-        TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize);
+    SDValue NegN0 = TLI.negateExpression(N0, DAG, LegalOperations, ForCodeSize);
+    SDValue NegN1 = TLI.negateExpression(N1, DAG, LegalOperations, ForCodeSize);
     return DAG.getNode(ISD::FMA, DL, VT, NegN0, NegN1, N2, Flags);
   }
 
   if (UnsafeFPMath) {
     if (N0CFP && N0CFP->isZero())
       return N2;
     if (N1CFP && N1CFP->isZero())
       return N2;
if (N1CFP && N2.getOpcode() == ISD::FNEG && N2.getOperand(0) == N0) {
                          DAG.getNode(ISD::FADD, DL, VT, N1,
                                      DAG.getConstantFP(-1.0, DL, VT), Flags),
                          Flags);
     }
   }
 
   // fold ((fma (fneg X), Y, (fneg Z)) -> fneg (fma X, Y, Z))
   // fold ((fma X, (fneg Y), (fneg Z)) -> fneg (fma X, Y, Z))
-  if (!TLI.isFNegFree(VT) &&
-      TLI.getNegatibleCost(SDValue(N, 0), DAG, LegalOperations, ForCodeSize) ==
-          TargetLowering::NegatibleCost::Cheaper)
-    return DAG.getNode(ISD::FNEG, DL, VT,
-                       TLI.getNegatedExpression(SDValue(N, 0), DAG,
-                                                LegalOperations, ForCodeSize),
-                       Flags);
+  if (!TLI.isFNegFree(VT))
+    if (SDValue Neg = TLI.getCheaperNegatedExpression(
+            SDValue(N, 0), DAG, LegalOperations, ForCodeSize))
+      return DAG.getNode(ISD::FNEG, DL, VT, Neg, Flags);
   return SDValue();
 }
 
 // Combine multiple FDIVs with the same divisor into multiple FMULs by the
 // reciprocal.
 // E.g., (a / D; b / D;) -> (recip = 1.0 / D; a * recip; b * recip)
 // Notice that this is not always beneficial. One reason is different targets
 // may have different costs for FDIV and FMUL, so sometimes the cost of two
if (Options.UnsafeFPMath || Flags.hasAllowReciprocal()) {
 
     // Fold into a reciprocal estimate and multiply instead of a real divide.
     if (SDValue RV = BuildDivEstimate(N0, N1, Flags))
       return RV;
   }
 
   // (fdiv (fneg X), (fneg Y)) -> (fdiv X, Y)
   if (isCheaperToUseNegatedFPOps(N0, N1)) {
-    SDValue Neg0 =
-        TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize);
-    SDValue Neg1 =
-        TLI.getNegatedExpression(N1, DAG, LegalOperations, ForCodeSize);
+    SDValue Neg0 = TLI.negateExpression(N0, DAG, LegalOperations, ForCodeSize);
+    SDValue Neg1 = TLI.negateExpression(N1, DAG, LegalOperations, ForCodeSize);
     return DAG.getNode(ISD::FDIV, SDLoc(N), VT, Neg0, Neg1, Flags);
   }
 
   return SDValue();
 }
 
 SDValue DAGCombiner::visitFREM(SDNode *N) {
   SDValue N0 = N->getOperand(0);

 SDValue DAGCombiner::visitFNEG(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   EVT VT = N->getValueType(0);
 
   // Constant fold FNEG.
   if (isConstantFPBuildVectorOrConstantFP(N0))
     return DAG.getNode(ISD::FNEG, SDLoc(N), VT, N0);
 
-  if (TLI.getNegatibleCost(N0, DAG, LegalOperations, ForCodeSize) !=
-      TargetLowering::NegatibleCost::Expensive)
-    return TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize);
+  if (SDValue NegN0 =
+          TLI.getNegatedExpression(N0, DAG, LegalOperations, ForCodeSize))
+    return NegN0;
 
   // -(X-Y) -> (Y-X) is unsafe because when X==Y, -0.0 != +0.0
   // FIXME: This is duplicated in getNegatibleCost, but getNegatibleCost doesn't
   // know it was called from a context with a nsz flag if the input fsub does
   // not.
   if (N0.getOpcode() == ISD::FSUB &&
       (DAG.getTarget().Options.NoSignedZerosFPMath ||
        N->getFlags().hasNoSignedZeros()) && N0.hasOneUse()) {

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

TargetLowering::getNegatibleCost(SDValue Op, SelectionDAG &DAG,
   if (!Op.hasOneUse()) {
     bool IsFreeExtend = Op.getOpcode() == ISD::FP_EXTEND &&
                         isFPExtFree(VT, Op.getOperand(0).getValueType());
 
     // If we already have the use of the negated floating constant, it is free
     // to negate it even it has multiple uses.
     bool IsFreeConstant =
         Op.getOpcode() == ISD::ConstantFP &&
-        !getNegatedExpression(Op, DAG, LegalOperations, ForCodeSize)
-             .use_empty();
+        !negateExpression(Op, DAG, LegalOperations, ForCodeSize).use_empty();
 
     if (!IsFreeExtend && !IsFreeConstant)
       return NegatibleCost::Expensive;
   }
 
   // Don't recurse exponentially.
   if (Depth > SelectionDAG::MaxRecursionDepth)
     return NegatibleCost::Expensive;
TargetLowering::getNegatibleCost(SDValue Op, SelectionDAG &DAG,
   case ISD::FSIN:
     return getNegatibleCost(Op.getOperand(0), DAG, LegalOperations, ForCodeSize,
                             Depth + 1);
   }
 
   return NegatibleCost::Expensive;
 }
 
-SDValue TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
-                                             bool LegalOps, bool OptForSize,
-                                             unsigned Depth) const {
+SDValue TargetLowering::negateExpression(SDValue Op, SelectionDAG &DAG,
   // fneg is removable even if it has multiple uses.
   if (Op.getOpcode() == ISD::FNEG)
     return Op.getOperand(0);
 
   assert(Depth <= SelectionDAG::MaxRecursionDepth &&
-         "getNegatedExpression doesn't match getNegatibleCost");
+         "negateExpression doesn't match getNegatibleCost");
 
   // Pre-increment recursion depth for use in recursive calls.
   ++Depth;
   const SDNodeFlags Flags = Op->getFlags();
   EVT VT = Op.getValueType();
   unsigned Opcode = Op.getOpcode();
   SDLoc DL(Op);
 
case ISD::FADD: {
     SDValue X = Op.getOperand(0), Y = Op.getOperand(1);
     assert((DAG.getTarget().Options.NoSignedZerosFPMath ||
             Flags.hasNoSignedZeros()) &&
            "Expected NSZ fp-flag");
 
     // fold (fneg (fadd X, Y)) -> (fsub (fneg X), Y)
     NegatibleCost CostX = getNegatibleCost(X, DAG, LegalOps, OptForSize, Depth);
     if (CostX != NegatibleCost::Expensive)
-      return DAG.getNode(
-          ISD::FSUB, DL, VT,
-          getNegatedExpression(X, DAG, LegalOps, OptForSize, Depth), Y, Flags);
+      return DAG.getNode(ISD::FSUB, DL, VT,
+                         negateExpression(X, DAG, LegalOps, OptForSize, Depth),
+                         Y, Flags);
 
     // fold (fneg (fadd X, Y)) -> (fsub (fneg Y), X)
-    return DAG.getNode(
-        ISD::FSUB, DL, VT,
-        getNegatedExpression(Y, DAG, LegalOps, OptForSize, Depth), X, Flags);
+    return DAG.getNode(ISD::FSUB, DL, VT,
+                       negateExpression(Y, DAG, LegalOps, OptForSize, Depth), X,
+                       Flags);
   }
   case ISD::FSUB: {
     SDValue X = Op.getOperand(0), Y = Op.getOperand(1);
     // fold (fneg (fsub 0, Y)) -> Y
     if (ConstantFPSDNode *C = isConstOrConstSplatFP(X, /*AllowUndefs*/ true))
       if (C->isZero())
         return Y;
 
     // fold (fneg (fsub X, Y)) -> (fsub Y, X)
     return DAG.getNode(ISD::FSUB, DL, VT, Y, X, Flags);
   }
   case ISD::FMUL:
   case ISD::FDIV: {
     SDValue X = Op.getOperand(0), Y = Op.getOperand(1);
     // fold (fneg (fmul X, Y)) -> (fmul (fneg X), Y)
     NegatibleCost CostX = getNegatibleCost(X, DAG, LegalOps, OptForSize, Depth);
     if (CostX != NegatibleCost::Expensive)
-      return DAG.getNode(
-          Opcode, DL, VT,
-          getNegatedExpression(X, DAG, LegalOps, OptForSize, Depth), Y, Flags);
+      return DAG.getNode(Opcode, DL, VT,
+                         negateExpression(X, DAG, LegalOps, OptForSize, Depth),
+                         Y, Flags);
 
     // fold (fneg (fmul X, Y)) -> (fmul X, (fneg Y))
-    return DAG.getNode(
-        Opcode, DL, VT, X,
-        getNegatedExpression(Y, DAG, LegalOps, OptForSize, Depth), Flags);
+    return DAG.getNode(Opcode, DL, VT, X,
+                       negateExpression(Y, DAG, LegalOps, OptForSize, Depth),
+                       Flags);
   }
   case ISD::FMA:
   case ISD::FMAD: {
     assert((DAG.getTarget().Options.NoSignedZerosFPMath ||
             Flags.hasNoSignedZeros()) &&
            "Expected NSZ fp-flag");
 
     SDValue X = Op.getOperand(0), Y = Op.getOperand(1), Z = Op.getOperand(2);
-    SDValue NegZ = getNegatedExpression(Z, DAG, LegalOps, OptForSize, Depth);
+    SDValue NegZ = negateExpression(Z, DAG, LegalOps, OptForSize, Depth);
     NegatibleCost CostX = getNegatibleCost(X, DAG, LegalOps, OptForSize, Depth);
     NegatibleCost CostY = getNegatibleCost(Y, DAG, LegalOps, OptForSize, Depth);
     if (CostX <= CostY) {
       // fold (fneg (fma X, Y, Z)) -> (fma (fneg X), Y, (fneg Z))
-      SDValue NegX = getNegatedExpression(X, DAG, LegalOps, OptForSize, Depth);
+      SDValue NegX = negateExpression(X, DAG, LegalOps, OptForSize, Depth);
       return DAG.getNode(Opcode, DL, VT, NegX, Y, NegZ, Flags);
     }
 
     // fold (fneg (fma X, Y, Z)) -> (fma X, (fneg Y), (fneg Z))
-    SDValue NegY = getNegatedExpression(Y, DAG, LegalOps, OptForSize, Depth);
+    SDValue NegY = negateExpression(Y, DAG, LegalOps, OptForSize, Depth);
     return DAG.getNode(Opcode, DL, VT, X, NegY, NegZ, Flags);
   }
 
   case ISD::FP_EXTEND:
   case ISD::FSIN:
-    return DAG.getNode(Opcode, DL, VT,
-                       getNegatedExpression(Op.getOperand(0), DAG, LegalOps,
-                                            OptForSize, Depth));
+    return DAG.getNode(
+        Opcode, DL, VT,
+        negateExpression(Op.getOperand(0), DAG, LegalOps, OptForSize, Depth));
   case ISD::FP_ROUND:
-    return DAG.getNode(ISD::FP_ROUND, DL, VT,
-                       getNegatedExpression(Op.getOperand(0), DAG, LegalOps,
-                                            OptForSize, Depth),
-                       Op.getOperand(1));
+    return DAG.getNode(
+        ISD::FP_ROUND, DL, VT,
+        negateExpression(Op.getOperand(0), DAG, LegalOps, OptForSize, Depth),
   }
 
   llvm_unreachable("Unknown code");
 }
 
 //===----------------------------------------------------------------------===//
 // Legalization Utilities
 //===----------------------------------------------------------------------===//

llvm/lib/Target/X86/X86ISelLowering.h

public:
     /// Returns whether computing the negated form of the specified expression
     /// is more expensive, the same cost or cheaper.
     NegatibleCost getNegatibleCost(SDValue Op, SelectionDAG &DAG,
                                    bool LegalOperations, bool ForCodeSize,
                                    unsigned Depth) const override;
 
     /// If getNegatibleCost returns Neutral/Cheaper, return the newly negated
     /// expression.
-    SDValue getNegatedExpression(SDValue Op, SelectionDAG &DAG,
-                                 bool LegalOperations, bool ForCodeSize,
-                                 unsigned Depth) const override;
+    SDValue negateExpression(SDValue Op, SelectionDAG &DAG,
 
     MachineBasicBlock *
     EmitInstrWithCustomInserter(MachineInstr &MI,
                                 MachineBasicBlock *MBB) const override;
 
     /// This method returns the name of a target specific DAG node.
     const char *getTargetNodeName(unsigned Opcode) const override;
 

llvm/lib/Target/X86/X86ISelLowering.cpp

if (Arg.getOpcode() == ISD::FMUL && (SVT == MVT::f32 || SVT == MVT::f64) &&
     SDValue Zero = DAG.getConstantFP(0.0, DL, VT);
     SDValue NewNode = DAG.getNode(X86ISD::FNMSUB, DL, VT, Arg.getOperand(0),
                                   Arg.getOperand(1), Zero);
     return DAG.getBitcast(OrigVT, NewNode);
   }
 
   bool CodeSize = DAG.getMachineFunction().getFunction().hasOptSize();
   bool LegalOperations = !DCI.isBeforeLegalizeOps();
-  if (TLI.getNegatibleCost(Arg, DAG, LegalOperations, CodeSize) !=
-      TargetLowering::NegatibleCost::Expensive)
-    return DAG.getBitcast(
-        OrigVT, TLI.getNegatedExpression(Arg, DAG, LegalOperations, CodeSize));
+  if (SDValue NegArg =
+          TLI.getNegatedExpression(Arg, DAG, LegalOperations, CodeSize))
+    return DAG.getBitcast(OrigVT, NegArg);
 
   return SDValue();
 }
 
 TargetLowering::NegatibleCost
 X86TargetLowering::getNegatibleCost(SDValue Op, SelectionDAG &DAG,
                                     bool LegalOperations, bool ForCodeSize,
                                     unsigned Depth) const {
case X86ISD::FRCP:
     return getNegatibleCost(Op.getOperand(0), DAG, LegalOperations, ForCodeSize,
                             Depth + 1);
   }
 
   return TargetLowering::getNegatibleCost(Op, DAG, LegalOperations, ForCodeSize,
                                           Depth);
 }
 
-SDValue X86TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
-                                                bool LegalOperations,
-                                                bool ForCodeSize,
-                                                unsigned Depth) const {
+SDValue X86TargetLowering::negateExpression(SDValue Op, SelectionDAG &DAG,
   // fneg patterns are removable even if they have multiple uses.
   if (SDValue Arg = isFNEG(DAG, Op.getNode(), Depth))
     return DAG.getBitcast(Op.getValueType(), Arg);
 
   EVT VT = Op.getValueType();
   EVT SVT = VT.getScalarType();
   unsigned Opc = Op.getOpcode();
   switch (Opc) {
   case ISD::FMA:
   case X86ISD::FMSUB:
   case X86ISD::FNMADD:
   case X86ISD::FNMSUB:
   case X86ISD::FMADD_RND:
   case X86ISD::FMSUB_RND:
   case X86ISD::FNMADD_RND:
   case X86ISD::FNMSUB_RND: {
     if (!Op.hasOneUse() || !Subtarget.hasAnyFMA() || !isTypeLegal(VT) ||
         !(SVT == MVT::f32 || SVT == MVT::f64) ||
         !isOperationLegal(ISD::FMA, VT))
       break;
 
     // This is always negatible for free but we might be able to remove some
     // extra operand negations as well.
     SmallVector<SDValue, 4> NewOps(Op.getNumOperands(), SDValue());
-    for (int i = 0; i != 3; ++i) {
-      NegatibleCost V = getNegatibleCost(Op.getOperand(i), DAG, LegalOperations,
-                                         ForCodeSize, Depth + 1);
-      if (V == NegatibleCost::Cheaper)
-        NewOps[i] = getNegatedExpression(Op.getOperand(i), DAG, LegalOperations,
-                                         ForCodeSize, Depth + 1);
-    }
+    for (int i = 0; i != 3; ++i)
+      NewOps[i] = getCheaperNegatedExpression(
+          Op.getOperand(i), DAG, LegalOperations, ForCodeSize, Depth + 1);
 
     bool NegA = !!NewOps[0];
     bool NegB = !!NewOps[1];
     bool NegC = !!NewOps[2];
     unsigned NewOpc = negateFMAOpcode(Opc, NegA != NegB, NegC, true);
 
     // Fill in the non-negated ops with the original values.
     for (int i = 0, e = Op.getNumOperands(); i != e; ++i)
       if (!NewOps[i])
         NewOps[i] = Op.getOperand(i);
     return DAG.getNode(NewOpc, SDLoc(Op), VT, NewOps);
   }
   case X86ISD::FRCP:
     return DAG.getNode(Opc, SDLoc(Op), VT,
-                       getNegatedExpression(Op.getOperand(0), DAG,
-                                            LegalOperations, ForCodeSize,
-                                            Depth + 1));
+                       negateExpression(Op.getOperand(0), DAG, LegalOperations,
+                                        ForCodeSize, Depth + 1));
+    break;
   }
 
-  return TargetLowering::getNegatedExpression(Op, DAG, LegalOperations,
-                                              ForCodeSize, Depth);
+  return TargetLowering::negateExpression(Op, DAG, LegalOperations, ForCodeSize,
+                                          Depth);
 }
 
 static SDValue lowerX86FPLogicOp(SDNode *N, SelectionDAG &DAG,
                                  const X86Subtarget &Subtarget) {
   MVT VT = N->getSimpleValueType(0);
   // If we have integer vector types available, use the integer opcodes.
   if (!VT.isVector() || !Subtarget.hasSSE2())
     return SDValue();
static SDValue combineFMA(SDNode *N, SelectionDAG &DAG,
 
   SDValue A = N->getOperand(IsStrict ? 1 : 0);
   SDValue B = N->getOperand(IsStrict ? 2 : 1);
   SDValue C = N->getOperand(IsStrict ? 3 : 2);
 
   auto invertIfNegative = [&DAG, &TLI, &DCI](SDValue &V) {
     bool CodeSize = DAG.getMachineFunction().getFunction().hasOptSize();
     bool LegalOperations = !DCI.isBeforeLegalizeOps();
-    if (TLI.getNegatibleCost(V, DAG, LegalOperations, CodeSize) ==
-        TargetLowering::NegatibleCost::Cheaper) {
-      V = TLI.getNegatedExpression(V, DAG, LegalOperations, CodeSize);
+    if (SDValue NegV = TLI.getCheaperNegatedExpression(V, DAG, LegalOperations,
+                                                       CodeSize)) {
+      V = NegV;
       return true;
     }
     // Look through extract_vector_elts. If it comes from an FNEG, create a
     // new extract from the FNEG input.
     if (V.getOpcode() == ISD::EXTRACT_VECTOR_ELT &&
         isNullConstant(V.getOperand(1))) {
       SDValue Vec = V.getOperand(0);
-      if (TLI.getNegatibleCost(Vec, DAG, LegalOperations, CodeSize) ==
-          TargetLowering::NegatibleCost::Cheaper) {
-        SDValue NegVal =
-            TLI.getNegatedExpression(Vec, DAG, LegalOperations, CodeSize);
+      if (SDValue NegV = TLI.getCheaperNegatedExpression(
+              Vec, DAG, LegalOperations, CodeSize)) {
         V = DAG.getNode(ISD::EXTRACT_VECTOR_ELT, SDLoc(V), V.getValueType(),
-                        NegVal, V.getOperand(1));
+                        NegV, V.getOperand(1));
         return true;
       }
     }
 
     return false;
   };
 
   // Do not convert the passthru input of scalar intrinsics.
static SDValue combineFMADDSUB(SDNode *N, SelectionDAG &DAG,
                                TargetLowering::DAGCombinerInfo &DCI) {
   SDLoc dl(N);
   EVT VT = N->getValueType(0);
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
   bool CodeSize = DAG.getMachineFunction().getFunction().hasOptSize();
   bool LegalOperations = !DCI.isBeforeLegalizeOps();
 
   SDValue N2 = N->getOperand(2);
-  if (TLI.getNegatibleCost(N2, DAG, LegalOperations, CodeSize) !=
-      TargetLowering::NegatibleCost::Cheaper)
-    return SDValue();
 
-  SDValue NegN2 = TLI.getNegatedExpression(N2, DAG, LegalOperations, CodeSize);
+  SDValue NegN2 =
+      TLI.getCheaperNegatedExpression(N2, DAG, LegalOperations, CodeSize);
+  if (!NegN2)
+    return SDValue();
   unsigned NewOpcode = negateFMAOpcode(N->getOpcode(), false, true, false);
 
   if (N->getNumOperands() == 4)
     return DAG.getNode(NewOpcode, dl, VT, N->getOperand(0), N->getOperand(1),
                        NegN2, N->getOperand(3));
   return DAG.getNode(NewOpcode, dl, VT, N->getOperand(0), N->getOperand(1),
                      NegN2);
 }