[DAGCombine] Checking the cost directly to improve the code readability

Call getNegatedExpression(Cost) and check the Cost to make the code more clear.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D78347

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 8edd90a..1a8242a 100644 (file)
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -527,7 +527,6 @@ namespace {
     bool isSetCCEquivalent(SDValue N, SDValue &LHS, SDValue &RHS,
                            SDValue &CC, bool MatchStrict = false) const;
     bool isOneUseSetCC(SDValue N) const;
-    bool isCheaperToUseNegatedFPOps(SDValue X, SDValue Y);
 
     SDValue SimplifyNodeWithTwoResults(SDNode *N, unsigned LoOp,
                                          unsigned HiOp);
@@ -12616,25 +12615,6 @@ SDValue DAGCombiner::visitFSUB(SDNode *N) {
   return SDValue();
 }
 
-/// Return true if both inputs are at least as cheap in negated form and at
-/// least one input is strictly cheaper in negated form.
-bool DAGCombiner::isCheaperToUseNegatedFPOps(SDValue X, SDValue Y) {
-  TargetLowering::NegatibleCost LHSNeg =
-      TLI.getNegatibleCost(X, DAG, LegalOperations, ForCodeSize);
-  if (TargetLowering::NegatibleCost::Expensive == LHSNeg)
-    return false;
-
-  TargetLowering::NegatibleCost RHSNeg =
-      TLI.getNegatibleCost(Y, DAG, LegalOperations, ForCodeSize);
-  if (TargetLowering::NegatibleCost::Expensive == RHSNeg)
-    return false;
-
-  // Both negated operands are at least as cheap as their counterparts.
-  // Check to see if at least one is cheaper negated.
-  return (TargetLowering::NegatibleCost::Cheaper == LHSNeg ||
-          TargetLowering::NegatibleCost::Cheaper == RHSNeg);
-}
-
 SDValue DAGCombiner::visitFMUL(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   SDValue N1 = N->getOperand(1);
@@ -12709,11 +12689,18 @@ SDValue DAGCombiner::visitFMUL(SDNode *N) {
       return DAG.getNode(ISD::FNEG, DL, VT, N0);
 
   // -N0 * -N1 --> N0 * N1
-  if (isCheaperToUseNegatedFPOps(N0, N1)) {
-    SDValue NegN0 = TLI.negateExpression(N0, DAG, LegalOperations, ForCodeSize);
-    SDValue NegN1 = TLI.negateExpression(N1, DAG, LegalOperations, ForCodeSize);
+  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);
-  }
 
   // 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)
@@ -12792,11 +12779,18 @@ SDValue DAGCombiner::visitFMA(SDNode *N) {
   }
 
   // (-N0 * -N1) + N2 --> (N0 * N1) + N2
-  if (isCheaperToUseNegatedFPOps(N0, N1)) {
-    SDValue NegN0 = TLI.negateExpression(N0, DAG, LegalOperations, ForCodeSize);
-    SDValue NegN1 = TLI.negateExpression(N1, DAG, LegalOperations, ForCodeSize);
+  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::FMA, DL, VT, NegN0, NegN1, N2, Flags);
-  }
 
   if (UnsafeFPMath) {
     if (N0CFP && N0CFP->isZero())
@@ -13061,11 +13055,18 @@ SDValue DAGCombiner::visitFDIV(SDNode *N) {
   }
 
   // (fdiv (fneg X), (fneg Y)) -> (fdiv X, Y)
-  if (isCheaperToUseNegatedFPOps(N0, N1)) {
-    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);
-  }
+  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::FDIV, SDLoc(N), VT, NegN0, NegN1, Flags);
 
   return SDValue();
 }

diff --git a/llvm/test/CodeGen/PowerPC/qpx-recipest.ll b/llvm/test/CodeGen/PowerPC/qpx-recipest.ll
index 2fdaa1f..4f3abd2 100644 (file)
--- a/llvm/test/CodeGen/PowerPC/qpx-recipest.ll
+++ b/llvm/test/CodeGen/PowerPC/qpx-recipest.ll
@@ -65,8 +65,8 @@ define <4 x double> @foof_fmf(<4 x double> %a, <4 x float> %b) nounwind {
 ; CHECK-NEXT:    addi 3, 3, .LCPI2_0@toc@l
 ; CHECK-NEXT:    qvlfsx 0, 0, 3
 ; CHECK-NEXT:    qvfmuls 4, 3, 3
-; CHECK-NEXT:    qvfnmsubs 2, 2, 0, 2
-; CHECK-NEXT:    qvfmadds 0, 2, 4, 0
+; CHECK-NEXT:    qvfmsubs 2, 2, 0, 2
+; CHECK-NEXT:    qvfnmsubs 0, 2, 4, 0
 ; CHECK-NEXT:    qvfmuls 0, 3, 0
 ; CHECK-NEXT:    qvfmul 1, 1, 0
 ; CHECK-NEXT:    blr
@@ -182,8 +182,8 @@ define <4 x float> @goo_fmf(<4 x float> %a, <4 x float> %b) nounwind {
 ; CHECK-NEXT:    addi 3, 3, .LCPI6_0@toc@l
 ; CHECK-NEXT:    qvlfsx 0, 0, 3
 ; CHECK-NEXT:    qvfmuls 4, 3, 3
-; CHECK-NEXT:    qvfnmsubs 2, 2, 0, 2
-; CHECK-NEXT:    qvfmadds 0, 2, 4, 0
+; CHECK-NEXT:    qvfmsubs 2, 2, 0, 2
+; CHECK-NEXT:    qvfnmsubs 0, 2, 4, 0
 ; CHECK-NEXT:    qvfmuls 0, 3, 0
 ; CHECK-NEXT:    qvfmuls 1, 1, 0
 ; CHECK-NEXT:    blr
@@ -408,8 +408,8 @@ define <4 x float> @goo3_fmf_denorm_on(<4 x float> %a) #0 {
 ; CHECK-NEXT:    addis 3, 2, .LCPI16_0@toc@ha
 ; CHECK-NEXT:    addi 3, 3, .LCPI16_0@toc@l
 ; CHECK-NEXT:    qvfmuls 4, 2, 2
-; CHECK-NEXT:    qvfnmsubs 3, 1, 0, 1
-; CHECK-NEXT:    qvfmadds 0, 3, 4, 0
+; CHECK-NEXT:    qvfmsubs 3, 1, 0, 1
+; CHECK-NEXT:    qvfnmsubs 0, 3, 4, 0
 ; CHECK-NEXT:    qvlfsx 3, 0, 3
 ; CHECK-NEXT:    addis 3, 2, .LCPI16_2@toc@ha
 ; CHECK-NEXT:    addi 3, 3, .LCPI16_2@toc@l
@@ -435,8 +435,8 @@ define <4 x float> @goo3_fmf_denorm_off(<4 x float> %a) #1 {
 ; CHECK-NEXT:    addis 3, 2, .LCPI17_0@toc@ha
 ; CHECK-NEXT:    addi 3, 3, .LCPI17_0@toc@l
 ; CHECK-NEXT:    qvfmuls 4, 2, 2
-; CHECK-NEXT:    qvfnmsubs 3, 1, 0, 1
-; CHECK-NEXT:    qvfmadds 0, 3, 4, 0
+; CHECK-NEXT:    qvfmsubs 3, 1, 0, 1
+; CHECK-NEXT:    qvfnmsubs 0, 3, 4, 0
 ; CHECK-NEXT:    qvlfsx 3, 0, 3
 ; CHECK-NEXT:    qvfmuls 0, 2, 0
 ; CHECK-NEXT:    qvfmuls 0, 0, 1