[Constants] If we already have a ConstantInt*, prefer to use isZero/isOne/isMinusOne instead of isNullValue/isOneValue/isAllOnesValue inherited from Constant. NFCI

Going through the Constant methods requires redetermining that the Constant is a ConstantInt and then calling isZero/isOne/isMinusOne.

llvm-svn: 307292
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index cdba006..29d1ba4 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -2148,7 +2148,7 @@
     if (I->getOpcode() == Instruction::Mul &&
         cast<Instruction>(I->user_back())->getOpcode() == Instruction::Add &&
         isa<ConstantInt>(Ops.back().Op) &&
-        cast<ConstantInt>(Ops.back().Op)->isAllOnesValue()) {
+        cast<ConstantInt>(Ops.back().Op)->isMinusOne()) {
       ValueEntry Tmp = Ops.pop_back_val();
       Ops.insert(Ops.begin(), Tmp);
     } else if (I->getOpcode() == Instruction::FMul &&