[PATCH] D134966: [DAG] Update foldSelectWithIdentityConstant to use llvm::isNeutralConstant

[Simon Pilgrim via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG61dc5014acf1: [DAG] Update foldSelectWithIdentityConstant to use llvm::isNeutralConstant (authored by RKSimon).

Changed prior to commit:
  https://reviews.llvm.org/D134966?vs=464278&id=464306#toc

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D134966/new/

https://reviews.llvm.org/D134966

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp


Index: llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -10749,7 +10749,9 @@
 
 bool llvm::isNeutralConstant(unsigned Opcode, SDNodeFlags Flags, SDValue V,
                              unsigned OperandNo) {
-  if (auto *Const = dyn_cast<ConstantSDNode>(V)) {
+  // NOTE: The cases should match with IR's ConstantExpr::getBinOpIdentity().
+  // TODO: Target-specific opcodes could be added.
+  if (auto *Const = isConstOrConstSplat(V)) {
     switch (Opcode) {
     case ISD::ADD:
     case ISD::OR:
@@ -10774,7 +10776,7 @@
     case ISD::SDIV:
       return OperandNo == 1 && Const->isOne();
     }
-  } else if (auto *ConstFP = dyn_cast<ConstantFPSDNode>(V)) {
+  } else if (auto *ConstFP = isConstOrConstSplatFP(V)) {
     switch (Opcode) {
     case ISD::FADD:
       return ConstFP->isZero() &&
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2202,45 +2202,16 @@
   SDValue TVal = N1.getOperand(1);
   SDValue FVal = N1.getOperand(2);
 
-  // TODO: The cases should match with IR's ConstantExpr::getBinOpIdentity().
-  // TODO: Target-specific opcodes could be added. Ex: "isCommutativeBinOp()".
-  // TODO: With fast-math (NSZ), allow the opposite-sign form of zero?
-  auto isIdentityConstantForOpcode = [](unsigned Opcode, SDValue V) {
-    if (ConstantFPSDNode *C = isConstOrConstSplatFP(V)) {
-      switch (Opcode) {
-      case ISD::FADD: // X + -0.0 --> X
-        return C->isZero() && C->isNegative();
-      case ISD::FSUB: // X - 0.0 --> X
-        return C->isZero() && !C->isNegative();
-      case ISD::FMUL: // X * 1.0 --> X
-      case ISD::FDIV: // X / 1.0 --> X
-        return C->isExactlyValue(1.0);
-      }
-    }
-    if (ConstantSDNode *C = isConstOrConstSplat(V)) {
-      switch (Opcode) {
-      case ISD::ADD: // X + 0 --> X
-      case ISD::SUB: // X - 0 --> X
-      case ISD::SHL: // X << 0 --> X
-      case ISD::SRA: // X s>> 0 --> X
-      case ISD::SRL: // X u>> 0 --> X
-        return C->isZero();
-      case ISD::MUL: // X * 1 --> X
-        return C->isOne();
-      }
-    }
-    return false;
-  };
-
   // This transform increases uses of N0, so freeze it to be safe.
   // binop N0, (vselect Cond, IDC, FVal) --> vselect Cond, N0, (binop N0, FVal)
-  if (isIdentityConstantForOpcode(Opcode, TVal)) {
+  unsigned OpNo = ShouldCommuteOperands ? 0 : 1;
+  if (isNeutralConstant(Opcode, N->getFlags(), TVal, OpNo)) {
     SDValue F0 = DAG.getFreeze(N0);
     SDValue NewBO = DAG.getNode(Opcode, SDLoc(N), VT, F0, FVal, N->getFlags());
     return DAG.getSelect(SDLoc(N), VT, Cond, F0, NewBO);
   }
   // binop N0, (vselect Cond, TVal, IDC) --> vselect Cond, (binop N0, TVal), N0
-  if (isIdentityConstantForOpcode(Opcode, FVal)) {
+  if (isNeutralConstant(Opcode, N->getFlags(), FVal, OpNo)) {
     SDValue F0 = DAG.getFreeze(N0);
     SDValue NewBO = DAG.getNode(Opcode, SDLoc(N), VT, F0, TVal, N->getFlags());
     return DAG.getSelect(SDLoc(N), VT, Cond, NewBO, F0);


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