[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/LoopStrengthReduce.cpp b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
index b4a3591..3638da1 100644
--- a/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp
@@ -2326,7 +2326,7 @@
                 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
             const ConstantInt *C = D->getValue();
             // Stride of one or negative one can have reuse with non-addresses.
-            if (C->isOne() || C->isAllOnesValue())
+            if (C->isOne() || C->isMinusOne())
               goto decline_post_inc;
             // Avoid weird situations.
             if (C->getValue().getMinSignedBits() >= 64 ||