Re-commit [OpenCL] AMDGCN: Fix size_t type

There was a premature cast to pointer type in emitPointerArithmetic which caused assertion in tests with assertion enabled.

llvm-svn: 279206
diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index dec8b7c..592b877 100644
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -306,8 +306,9 @@
     }
     LongDoubleWidth = LongDoubleAlign = 128;
 
-    assert(PointerWidth == 32 || PointerWidth == 64);
-    bool Is32BitArch = PointerWidth == 32;
+    unsigned MaxPointerWidth = getMaxPointerWidth();
+    assert(MaxPointerWidth == 32 || MaxPointerWidth == 64);
+    bool Is32BitArch = MaxPointerWidth == 32;
     SizeType = Is32BitArch ? UnsignedInt : UnsignedLong;
     PtrDiffType = Is32BitArch ? SignedInt : SignedLong;
     IntPtrType = Is32BitArch ? SignedInt : SignedLong;