[InstCombine] In foldSelectIntoOp, avoid creating a Constant before we know for sure...

Instead of creating a Constant and then calling m_APInt with it (which will always return true). Just create an APInt initially, and use that for the checks in isSelect01 function. If it turns out we do need the Constant, create it from the APInt.

This is a refactor for a future patch that will do some more checks of the constant values here.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312517 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 83aeda5..2641602 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -101,7 +101,7 @@ static unsigned getSelectFoldableOperands(BinaryOperator *I) {
 
 /// For the same transformation as the previous function, return the identity
 /// constant that goes into the select.
-static Constant *getSelectFoldableConstant(BinaryOperator *I) {
+static APInt getSelectFoldableConstant(BinaryOperator *I) {
   switch (I->getOpcode()) {
   default: llvm_unreachable("This cannot happen!");
   case Instruction::Add:
@@ -111,11 +111,11 @@ static Constant *getSelectFoldableConstant(BinaryOperator *I) {
   case Instruction::Shl:
   case Instruction::LShr:
   case Instruction::AShr:
-    return Constant::getNullValue(I->getType());
+    return APInt::getNullValue(I->getType()->getScalarSizeInBits());
   case Instruction::And:
-    return Constant::getAllOnesValue(I->getType());
+    return APInt::getAllOnesValue(I->getType()->getScalarSizeInBits());
   case Instruction::Mul:
-    return ConstantInt::get(I->getType(), 1);
+    return APInt(I->getType()->getScalarSizeInBits(), 1);
   }
 }
 
@@ -219,16 +219,11 @@ Instruction *InstCombiner::foldSelectOpOp(SelectInst &SI, Instruction *TI,
   return BinaryOperator::Create(BO->getOpcode(), Op0, Op1);
 }
 
-static bool isSelect01(Constant *C1, Constant *C2) {
-  const APInt *C1I, *C2I;
-  if (!match(C1, m_APInt(C1I)))
+static bool isSelect01(const APInt &C1I, const APInt &C2I) {
+  if (!C1I.isNullValue() && !C2I.isNullValue()) // One side must be zero.
     return false;
-  if (!match(C2, m_APInt(C2I)))
-    return false;
-  if (!C1I->isNullValue() && !C2I->isNullValue()) // One side must be zero.
-    return false;
-  return C1I->isOneValue() || C1I->isAllOnesValue() ||
-         C2I->isOneValue() || C2I->isAllOnesValue();
+  return C1I.isOneValue() || C1I.isAllOnesValue() ||
+         C2I.isOneValue() || C2I.isAllOnesValue();
 }
 
 /// Try to fold the select into one of the operands to allow further
@@ -248,11 +243,14 @@ Instruction *InstCombiner::foldSelectIntoOp(SelectInst &SI, Value *TrueVal,
         }
 
         if (OpToFold) {
-          Constant *C = getSelectFoldableConstant(TVI);
+          APInt CI = getSelectFoldableConstant(TVI);
           Value *OOp = TVI->getOperand(2-OpToFold);
           // Avoid creating select between 2 constants unless it's selecting
           // between 0, 1 and -1.
-          if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
+          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);
             Value *NewSel = Builder.CreateSelect(SI.getCondition(), OOp, C);
             NewSel->takeName(TVI);
             BinaryOperator *BO = BinaryOperator::Create(TVI->getOpcode(),
@@ -276,11 +274,14 @@ Instruction *InstCombiner::foldSelectIntoOp(SelectInst &SI, Value *TrueVal,
         }
 
         if (OpToFold) {
-          Constant *C = getSelectFoldableConstant(FVI);
+          APInt CI = getSelectFoldableConstant(FVI);
           Value *OOp = FVI->getOperand(2-OpToFold);
           // Avoid creating select between 2 constants unless it's selecting
           // between 0, 1 and -1.
-          if (!isa<Constant>(OOp) || isSelect01(C, cast<Constant>(OOp))) {
+          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);
             Value *NewSel = Builder.CreateSelect(SI.getCondition(), C, OOp);
             NewSel->takeName(FVI);
             BinaryOperator *BO = BinaryOperator::Create(FVI->getOpcode(),