Fix array sizes where address space is not yet known

[kzhuravl]

Summary

For variables in generic address spaces, for example:

unsigned char V[6442450944];
...

the address space is not yet known when we get into *getConstantArrayType*, it is 0. AMDGCN target's address space 0 has 32 bits pointers, so when we call *getPointerWidth* with 0, the array size is trimmed to 32 bits, which is not right.

[kzhuravl]

I am not sure if this is the right way to fix it.

[yaxunl]

lib/AST/ASTContext.cpp

2696 ↗

(On Diff #91404)

Can we just use getMaxPointerWidth instead? If we cannot determine the pointer size, using max pointer size makes sense. Also can you add a ToDo comment about this. Ideally we could get a better fix later.

cfe/trunk/lib/AST/ASTContext.cpp

QualType ASTContext::getConstantArrayType(QualType EltTy,
                                           unsigned IndexTypeQuals) const {
   assert((EltTy->isDependentType() ||
           EltTy->isIncompleteType() || EltTy->isConstantSizeType()) &&
          "Constant array of VLAs is illegal!");
 
   // Convert the array size into a canonical width matching the pointer size for
   // the target.
   llvm::APInt ArySize(ArySizeIn);
-  ArySize =
-    ArySize.zextOrTrunc(Target->getPointerWidth(getTargetAddressSpace(EltTy)));
+  ArySize = ArySize.zextOrTrunc(Target->getMaxPointerWidth());
 
   llvm::FoldingSetNodeID ID;
   ConstantArrayType::Profile(ID, EltTy, ArySize, ASM, IndexTypeQuals);
 
   void *InsertPos = nullptr;
   if (ConstantArrayType *ATP =
       ConstantArrayTypes.FindNodeOrInsertPos(ID, InsertPos))
     return QualType(ATP, 0);

cfe/trunk/test/CodeGenOpenCL/amdgcn-large-globals.cl

+// REQUIRES: amdgpu-registered-target
+// RUN: %clang_cc1 -cl-std=CL2.0 -triple amdgcn-unknown-unknown -S -emit-llvm -o - %s | FileCheck %s
+
+// CHECK: @One = common local_unnamed_addr addrspace(1) global [6442450944 x i8] zeroinitializer, align 1
+unsigned char One[6442450944];
+// CHECK: @Two = common local_unnamed_addr addrspace(1) global [6442450944 x i32] zeroinitializer, align 4
+global unsigned int Two[6442450944];
+ 
+kernel void large_globals(unsigned int id) {
+  One[id] = id;
+  Two[id + 1] = id + 1;
+}