Revert "[SDAG] remove use restriction in isNegatibleForFree() when called from getNegatedExpression()"

This reverts commit d1f0bdf2d2df9bdf11ee2ddfff3df50e53f2f042.
The patch can cause infinite loops in DAGCombiner.

3 files changed, 20 insertions, 26 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 05011aebb9d..f8afdaf086a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -5413,21 +5413,18 @@ verifyReturnAddressArgumentIsConstant(SDValue Op, SelectionDAG &DAG) const {
 
 char TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
                                         bool LegalOperations, bool ForCodeSize,
-                                        bool EnableUseCheck,
                                         unsigned Depth) const {
   // fneg is removable even if it has multiple uses.
   if (Op.getOpcode() == ISD::FNEG)
     return 2;
 
-  // If the caller requires checking uses, don't allow anything with multiple
-  // uses unless we know it is free.
+  // Don't allow anything with multiple uses unless we know it is free.
   EVT VT = Op.getValueType();
   const SDNodeFlags Flags = Op->getFlags();
   const TargetOptions &Options = DAG.getTarget().Options;
-  if (EnableUseCheck)
-    if (!Op.hasOneUse() && !(Op.getOpcode() == ISD::FP_EXTEND &&
-                             isFPExtFree(VT, Op.getOperand(0).getValueType())))
-      return 0;
+  if (!Op.hasOneUse() && !(Op.getOpcode() == ISD::FP_EXTEND &&
+                           isFPExtFree(VT, Op.getOperand(0).getValueType())))
+    return 0;
 
   // Don't recurse exponentially.
   if (Depth > SelectionDAG::MaxRecursionDepth)
@@ -5471,11 +5468,11 @@ char TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
 
     // fold (fneg (fadd A, B)) -> (fsub (fneg A), B)
     if (char V = isNegatibleForFree(Op.getOperand(0), DAG, LegalOperations,
-                                    ForCodeSize, EnableUseCheck, Depth + 1))
+                                    ForCodeSize, Depth + 1))
       return V;
     // fold (fneg (fadd A, B)) -> (fsub (fneg B), A)
     return isNegatibleForFree(Op.getOperand(1), DAG, LegalOperations,
-                              ForCodeSize, EnableUseCheck, Depth + 1);
+                              ForCodeSize, Depth + 1);
   case ISD::FSUB:
     // We can't turn -(A-B) into B-A when we honor signed zeros.
     if (!Options.NoSignedZerosFPMath && !Flags.hasNoSignedZeros())
@@ -5488,7 +5485,7 @@ char TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
   case ISD::FDIV:
     // fold (fneg (fmul X, Y)) -> (fmul (fneg X), Y) or (fmul X, (fneg Y))
     if (char V = isNegatibleForFree(Op.getOperand(0), DAG, LegalOperations,
-                                    ForCodeSize, EnableUseCheck, Depth + 1))
+                                    ForCodeSize, Depth + 1))
       return V;
 
     // Ignore X * 2.0 because that is expected to be canonicalized to X + X.
@@ -5497,7 +5494,7 @@ char TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
         return 0;
 
     return isNegatibleForFree(Op.getOperand(1), DAG, LegalOperations,
-                              ForCodeSize, EnableUseCheck, Depth + 1);
+                              ForCodeSize, Depth + 1);
 
   case ISD::FMA:
   case ISD::FMAD: {
@@ -5507,15 +5504,15 @@ char TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
     // fold (fneg (fma X, Y, Z)) -> (fma (fneg X), Y, (fneg Z))
     // fold (fneg (fma X, Y, Z)) -> (fma X, (fneg Y), (fneg Z))
     char V2 = isNegatibleForFree(Op.getOperand(2), DAG, LegalOperations,
-                                 ForCodeSize, EnableUseCheck, Depth + 1);
+                                 ForCodeSize, Depth + 1);
     if (!V2)
       return 0;
 
     // One of Op0/Op1 must be cheaply negatible, then select the cheapest.
     char V0 = isNegatibleForFree(Op.getOperand(0), DAG, LegalOperations,
-                                 ForCodeSize, EnableUseCheck, Depth + 1);
+                                 ForCodeSize, Depth + 1);
     char V1 = isNegatibleForFree(Op.getOperand(1), DAG, LegalOperations,
-                                 ForCodeSize, EnableUseCheck, Depth + 1);
+                                 ForCodeSize, Depth + 1);
     char V01 = std::max(V0, V1);
     return V01 ? std::max(V01, V2) : 0;
   }
@@ -5524,7 +5521,7 @@ char TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
   case ISD::FP_ROUND:
   case ISD::FSIN:
     return isNegatibleForFree(Op.getOperand(0), DAG, LegalOperations,
-                              ForCodeSize, EnableUseCheck, Depth + 1);
+                              ForCodeSize, Depth + 1);
   }
 
   return 0;
@@ -5568,7 +5565,7 @@ SDValue TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
 
     // fold (fneg (fadd A, B)) -> (fsub (fneg A), B)
     if (isNegatibleForFree(Op.getOperand(0), DAG, LegalOperations, ForCodeSize,
-                           false, Depth + 1))
+                           Depth + 1))
       return DAG.getNode(ISD::FSUB, SDLoc(Op), Op.getValueType(),
                          getNegatedExpression(Op.getOperand(0), DAG,
                                               LegalOperations, ForCodeSize,
@@ -5595,7 +5592,7 @@ SDValue TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
   case ISD::FDIV:
     // fold (fneg (fmul X, Y)) -> (fmul (fneg X), Y)
     if (isNegatibleForFree(Op.getOperand(0), DAG, LegalOperations, ForCodeSize,
-                           false, Depth + 1))
+                           Depth + 1))
       return DAG.getNode(Op.getOpcode(), SDLoc(Op), Op.getValueType(),
                          getNegatedExpression(Op.getOperand(0), DAG,
                                               LegalOperations, ForCodeSize,
@@ -5619,9 +5616,9 @@ SDValue TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
                                         ForCodeSize, Depth + 1);
 
     char V0 = isNegatibleForFree(Op.getOperand(0), DAG, LegalOperations,
-                                 ForCodeSize, false, Depth + 1);
+                                 ForCodeSize, Depth + 1);
     char V1 = isNegatibleForFree(Op.getOperand(1), DAG, LegalOperations,
-                                 ForCodeSize, false, Depth + 1);
+                                 ForCodeSize, Depth + 1);
     if (V0 >= V1) {
       // fold (fneg (fma X, Y, Z)) -> (fma (fneg X), Y, (fneg Z))
       SDValue Neg0 = getNegatedExpression(
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index cdb588ddb8a..866ee5b9a60 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -41898,7 +41898,6 @@ static SDValue combineFneg(SDNode *N, SelectionDAG &DAG,
 char X86TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
                                            bool LegalOperations,
                                            bool ForCodeSize,
-                                           bool EnableUseCheck,
                                            unsigned Depth) const {
   // fneg patterns are removable even if they have multiple uses.
   if (isFNEG(DAG, Op.getNode(), Depth))
@@ -41927,7 +41926,7 @@ char X86TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
     // extra operand negations as well.
     for (int i = 0; i != 3; ++i) {
       char V = isNegatibleForFree(Op.getOperand(i), DAG, LegalOperations,
-                                  ForCodeSize, EnableUseCheck, Depth + 1);
+                                  ForCodeSize, Depth + 1);
       if (V == 2)
         return V;
     }
@@ -41936,8 +41935,7 @@ char X86TargetLowering::isNegatibleForFree(SDValue Op, SelectionDAG &DAG,
   }
 
   return TargetLowering::isNegatibleForFree(Op, DAG, LegalOperations,
-                                            ForCodeSize, EnableUseCheck,
-                                            Depth);
+                                            ForCodeSize, Depth);
 }
 
 SDValue X86TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
@@ -41969,7 +41967,7 @@ SDValue X86TargetLowering::getNegatedExpression(SDValue Op, SelectionDAG &DAG,
     SmallVector<SDValue, 4> NewOps(Op.getNumOperands(), SDValue());
     for (int i = 0; i != 3; ++i) {
       char V = isNegatibleForFree(Op.getOperand(i), DAG, LegalOperations,
-                                  ForCodeSize, false, Depth + 1);
+                                  ForCodeSize, Depth + 1);
       if (V == 2)
         NewOps[i] = getNegatedExpression(Op.getOperand(i), DAG, LegalOperations,
                                          ForCodeSize, Depth + 1);
diff --git a/llvm/lib/Target/X86/X86ISelLowering.h b/llvm/lib/Target/X86/X86ISelLowering.h
index 3bbf3b59ac5..01612006413 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.h
+++ b/llvm/lib/Target/X86/X86ISelLowering.h
@@ -809,8 +809,7 @@ namespace llvm {
     /// for the same cost as the expression itself, or 2 if we can compute the
     /// negated form more cheaply than the expression itself. Else return 0.
     char isNegatibleForFree(SDValue Op, SelectionDAG &DAG, bool LegalOperations,
-                            bool ForCodeSize, bool EnableUseCheck,
-                            unsigned Depth) const override;
+                            bool ForCodeSize, unsigned Depth) const override;
 
     /// If isNegatibleForFree returns true, return the newly negated expression.
     SDValue getNegatedExpression(SDValue Op, SelectionDAG &DAG,