[APInt] Use lshrInPlace to replace lshr where possible

This patch uses lshrInPlace to replace code where the object that lshr is called on is being overwritten with the result.

This adds an lshrInPlace(const APInt &) version as well.

Differential Revision: https://reviews.llvm.org/D32155

llvm-svn: 300566
diff --git a/llvm/lib/IR/ConstantFold.cpp b/llvm/lib/IR/ConstantFold.cpp
index bba2306..80b1170 100644
--- a/llvm/lib/IR/ConstantFold.cpp
+++ b/llvm/lib/IR/ConstantFold.cpp
@@ -223,7 +223,7 @@
   if (ConstantInt *CI = dyn_cast<ConstantInt>(C)) {
     APInt V = CI->getValue();
     if (ByteStart)
-      V = V.lshr(ByteStart*8);
+      V.lshrInPlace(ByteStart*8);
     V = V.trunc(ByteSize*8);
     return ConstantInt::get(CI->getContext(), V);
   }