[PATCH] Support for address space casting in order to map these on the new 'addrspacecast' IR instruction

[Michele Scandale]

  I don't know if it's fine (and correct) to introduce the concept of address space casting at semantic level.

  So as alternative solution I propose also this non-intrusive alternative patch: here I've just fixed the code generation of scalar bitcast. Still there is an incoherence, because a semantic *bitcast* is translated in an operation that may not correspond to a bitcast in the LLVM IR (addrspacecast is assumed to represent whatever kind of conversion that may imply value and size changes).

  What do you think?

Hi rjmccall, rsmith,

http://llvm-reviews.chandlerc.com/D2241

CHANGE SINCE LAST DIFF
  http://llvm-reviews.chandlerc.com/D2241?vs=5708&id=5723#toc

Files:
  lib/CodeGen/CGExprScalar.cpp
  test/CodeGenOpenCL/address-spaces-cast.cl

Index: lib/CodeGen/CGExprScalar.cpp
===================================================================
--- lib/CodeGen/CGExprScalar.cpp
+++ lib/CodeGen/CGExprScalar.cpp
@@ -1299,6 +1299,8 @@
   case CK_AnyPointerToBlockPointerCast:
   case CK_BitCast: {
     Value *Src = Visit(const_cast<Expr*>(E));
+    if (E->getType()->isPointerType() && DestTy->isPointerType())
+      return Builder.CreatePointerCast(Src, ConvertType(DestTy));
     return Builder.CreateBitCast(Src, ConvertType(DestTy));
   }
   case CK_AtomicToNonAtomic:
Index: test/CodeGenOpenCL/address-spaces-cast.cl
===================================================================
--- test/CodeGenOpenCL/address-spaces-cast.cl
+++ test/CodeGenOpenCL/address-spaces-cast.cl
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 %s -ffake-address-space-map -emit-llvm -o - | FileCheck %s
+
+#define NULL ((void*)0)
+
+void explicit_cast_between_address_space(int i, __local int *A) {
+// CHECK: explicit_cast_between_address_space
+	__global int *b;
+
+	b = i > 42 ? (__global int *)A : NULL;
+//CHECK: addrspacecast
+
+	if (b)
+	  A[0] = b[5];
+}
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