[NFC] Minor fix to tryEmitAbstract type in EmitCXXNewAllocSize

In EmitCXXNewAllocSize, when handling a constant array size, we were calling
tryEmitAbstract with the type of the object being allocated. This worked out
because the type was always a pointer and tryEmitAbstract only ends up using
the size of the type to extend or truncate the constant, and in this case
the destination type should be size_t, which is the same size as the pointer.
So, this change fixes the type, but it makes no functional difference with
the current constant emitter implementation.

Author: andykaylor

clang/lib/CodeGen/CGExprCXX.cpp

@@ -732,8 +732,8 @@ static llvm::Value *EmitCXXNewAllocSize(CodeGenFunction &CGF,
   // Emit the array size expression.
   // We multiply the size of all dimensions for NumElements.
   // e.g for 'int[2][3]', ElemType is 'int' and NumElements is 6.
-  numElements =
-    ConstantEmitter(CGF).tryEmitAbstract(*e->getArraySize(), e->getType());
+  numElements = ConstantEmitter(CGF).tryEmitAbstract(
+      *e->getArraySize(), CGF.getContext().getSizeType());
   if (!numElements)
     numElements = CGF.EmitScalarExpr(*e->getArraySize());
   assert(isa<llvm::IntegerType>(numElements->getType()));