[InstCombine][NFC] Use ConstantExpr::getBinOpIdentity

Delete duplicate implementation getSelectFoldableConstant and
replace with ConstantExpr::getBinOpIdentity.

Differential Revision: https://reviews.llvm.org/D89839

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
index b8d4ddd..2150bd0 100644 (file)
--- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -259,26 +259,6 @@ static unsigned getSelectFoldableOperands(BinaryOperator *I) {
   }
 }
 
-/// For the same transformation as the previous function, return the identity
-/// constant that goes into the select.
-static APInt getSelectFoldableConstant(BinaryOperator *I) {
-  switch (I->getOpcode()) {
-  default: llvm_unreachable("This cannot happen!");
-  case Instruction::Add:
-  case Instruction::Sub:
-  case Instruction::Or:
-  case Instruction::Xor:
-  case Instruction::Shl:
-  case Instruction::LShr:
-  case Instruction::AShr:
-    return APInt::getNullValue(I->getType()->getScalarSizeInBits());
-  case Instruction::And:
-    return APInt::getAllOnesValue(I->getType()->getScalarSizeInBits());
-  case Instruction::Mul:
-    return APInt(I->getType()->getScalarSizeInBits(), 1);
-  }
-}
-
 /// We have (select c, TI, FI), and we know that TI and FI have the same opcode.
 Instruction *InstCombinerImpl::foldSelectOpOp(SelectInst &SI, Instruction *TI,
                                               Instruction *FI) {
@@ -434,14 +414,15 @@ Instruction *InstCombinerImpl::foldSelectIntoOp(SelectInst &SI, Value *TrueVal,
         }
 
         if (OpToFold) {
-          APInt CI = getSelectFoldableConstant(TVI);
+          Constant *C = ConstantExpr::getBinOpIdentity(TVI->getOpcode(),
+                                                       TVI->getType(), true);
           Value *OOp = TVI->getOperand(2-OpToFold);
           // Avoid creating select between 2 constants unless it's selecting
           // between 0, 1 and -1.
           const APInt *OOpC;
           bool OOpIsAPInt = match(OOp, m_APInt(OOpC));
-          if (!isa<Constant>(OOp) || (OOpIsAPInt && isSelect01(CI, *OOpC))) {
-            Value *C = ConstantInt::get(OOp->getType(), CI);
+          if (!isa<Constant>(OOp) ||
+              (OOpIsAPInt && isSelect01(C->getUniqueInteger(), *OOpC))) {
             Value *NewSel = Builder.CreateSelect(SI.getCondition(), OOp, C);
             NewSel->takeName(TVI);
             BinaryOperator *BO = BinaryOperator::Create(TVI->getOpcode(),
@@ -465,14 +446,15 @@ Instruction *InstCombinerImpl::foldSelectIntoOp(SelectInst &SI, Value *TrueVal,
         }
 
         if (OpToFold) {
-          APInt CI = getSelectFoldableConstant(FVI);
+          Constant *C = ConstantExpr::getBinOpIdentity(FVI->getOpcode(),
+                                                       FVI->getType(), true);
           Value *OOp = FVI->getOperand(2-OpToFold);
           // Avoid creating select between 2 constants unless it's selecting
           // between 0, 1 and -1.
           const APInt *OOpC;
           bool OOpIsAPInt = match(OOp, m_APInt(OOpC));
-          if (!isa<Constant>(OOp) || (OOpIsAPInt && isSelect01(CI, *OOpC))) {
-            Value *C = ConstantInt::get(OOp->getType(), CI);
+          if (!isa<Constant>(OOp) ||
+              (OOpIsAPInt && isSelect01(C->getUniqueInteger(), *OOpC))) {
             Value *NewSel = Builder.CreateSelect(SI.getCondition(), C, OOp);
             NewSel->takeName(FVI);
             BinaryOperator *BO = BinaryOperator::Create(FVI->getOpcode(),