[llvm] r312517 - [InstCombine] In foldSelectIntoOp, avoid creating a Constant before we know for sure we're going to use it and avoid an unnecessary call to m_APInt.

[Craig Topper via llvm-commits]

Author: ctopper
Date: Mon Sep  4 22:26:36 2017
New Revision: 312517

URL: http://llvm.org/viewvc/llvm-project?rev=312517&view=rev
Log:
[InstCombine] In foldSelectIntoOp, avoid creating a Constant before we know for sure we're going to use it and avoid an unnecessary call to m_APInt.

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.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp?rev=312517&r1=312516&r2=312517&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp Mon Sep  4 22:26:36 2017
@@ -101,7 +101,7 @@ static unsigned getSelectFoldableOperand
 
 /// 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 *getSelectFoldableConsta
   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::foldSelectOpO
   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::foldSelectInt
         }
 
         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::foldSelectInt
         }
 
         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(),