[SYCL] Insert implicit addrspacecast when casting between different AS

When default address space values in C++ are CodeGen'ed into different
address spaces in LLVM IR, we must ensure that an addrspacecast is
emitted before a bitcast.

Signed-off-by: Andrew Savonichev <andrew.savonichev@intel.com>

Author: Andrew Savonichev

clang/lib/CodeGen/CGExprScalar.cpp

@@ -1987,10 +1987,24 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     Value *Src = Visit(const_cast<Expr*>(E));
     llvm::Type *SrcTy = Src->getType();
     llvm::Type *DstTy = ConvertType(DestTy);
+    bool NeedAddrspaceCast = false;
     if (SrcTy->isPtrOrPtrVectorTy() && DstTy->isPtrOrPtrVectorTy() &&
         SrcTy->getPointerAddressSpace() != DstTy->getPointerAddressSpace()) {
-      llvm_unreachable("wrong cast for pointers in different address spaces"
-                       "(must be an address space cast)!");
+      // If we have the same address space in AST, which is then codegen'ed to
+      // different address spaces in IR, then an address space cast should be
+      // valid.
+      //
+      // This is the case for SYCL, where both types have Default address space
+      // in AST, but in IR one of them may be in opencl_private, and another in
+      // opencl_generic address space:
+      //
+      //   int arr[5]; // automatic variable, default AS in AST, private AS in
+      //   IR char* p = arr; // default AS in AST, generic AS in IR
+      //
+      if (E->getType().getAddressSpace() != DestTy.getAddressSpace())
+        llvm_unreachable("wrong cast for pointers in different address spaces"
+                         "(must be an address space cast)!");
+      NeedAddrspaceCast = true;
     }
 
     if (CGF.SanOpts.has(SanitizerKind::CFIUnrelatedCast)) {
@@ -2025,6 +2039,13 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
           CGF.getDebugInfo()->
               addHeapAllocSiteMetadata(CI, CE->getType(), CE->getExprLoc());
 
+    if (NeedAddrspaceCast) {
+      llvm::Type *SrcPointeeTy = Src->getType()->getPointerElementType();
+      llvm::Type *SrcNewAS = llvm::PointerType::get(
+          SrcPointeeTy, cast<llvm::PointerType>(DstTy)->getAddressSpace());
+
+      Src = Builder.CreateAddrSpaceCast(Src, SrcNewAS);
+    }
     return Builder.CreateBitCast(Src, DstTy);
   }
   case CK_AddressSpaceConversion: {

clang/test/CodeGenSYCL/address-space-new.cpp

@@ -7,13 +7,36 @@ void test() {
   // CHECK-NEW:    @_ZZ4testvE3foo = internal addrspace(1) constant i32 66, align 4
 
   // CHECK: @[[STR:[.a-zA-Z0-9_]+]] = private unnamed_addr constant [14 x i8] c"Hello, world!\00", align 1
+
+  // CHECK: %[[ARR:[a-zA-Z0-9]+]] = alloca [42 x i32]
+
   int i = 0;
   int *pptr = &i;
   // CHECK-LEGACY: store i32* %i, i32** %pptr
   // CHECK-NEW: %[[GEN:[0-9]+]] = addrspacecast i32* %i to i32 addrspace(4)*
   // CHECK-NEW: store i32 addrspace(4)* %[[GEN]], i32 addrspace(4)** %pptr
   *pptr = foo;
 
+  int var23 = 23;
+  char *cp = (char *)&var23;
+  *cp = 41;
+  // CHECK: store i32 23, i32* %[[VAR:[a-zA-Z0-9]+]]
+  // CHECK-OLD: [[VARCAST:[a-zA-Z0-9]+]] = bitcast i32* %[[VAR]] to i8*
+  // CHECK-OLD: store i8* %[[VARCAST]], i8** %{{.*}}
+  // CHECK-NEW: [[VARAS:[a-zA-Z0-9]+]] = addrspacecast i32* %[[VAR]] to i32 addrspace(4)*
+  // CHECK-NEW: [[VARCAST:[a-zA-Z0-9]+]] = bitcast i32 addrspace(4)* %[[VARAS]] to i8 addrspace(4)*
+  // CHECK-NEW: store i8 addrspace(4)* %[[VARCAST]], i8 addrspace(4)** %{{.*}}
+
+  int arr[42];
+  char *cpp = (char *)arr;
+  *cpp = 43;
+  // CHECK:     %[[ARRDECAY:[a-zA-Z0-9]+]] = getelementptr inbounds [42 x i32], [42 x i32]* %[[ARR]], i64 0, i64 0
+  // CHECK-OLD: [[ARRCAST:[a-zA-Z0-9]+]] = bitcast i32* %[[ARRDECAY]] to i8*
+  // CHECK-OLD: store i8* %[[ARRCAST]], i8** %{{.*}}
+  // CHECK-NEW: %[[ARRAS:[a-zA-Z0-9]+]] = addrspacecast i32* %[[ARRDECAY]] to i32 addrspace(4)*
+  // CHECK-NEW: %[[ARRCAST:[a-zA-Z0-9]+]] = bitcast i32 addrspace(4)* %[[ARRAS]] to i8 addrspace(4)*
+  // CHECK-NEW: store i8 addrspace(4)* %[[ARRCAST]], i8 addrspace(4)** %{{.*}}
+
   const char *str = "Hello, world!";
   // CHECK-LEGACY: store i8* getelementptr inbounds ([14 x i8], [14 x i8]* @[[STR]], i64 0, i64 0), i8** %{{.*}}, align 8
   // CHECK-NEW: store i8 addrspace(4)* addrspacecast (i8* getelementptr inbounds ([14 x i8], [14 x i8]* @[[STR]], i64 0, i64 0) to i8 addrspace(4)*), i8 addrspace(4)** %{{.*}}, align 8