[SYCL] Addrspace cast phi operands when lowering conditional operator

clang/lib/CodeGen/CGExpr.cpp

@@ -4279,10 +4279,35 @@ EmitConditionalOperatorLValue(const AbstractConditionalOperator *expr) {
   EmitBlock(contBlock);
 
   if (lhs && rhs) {
-    llvm::PHINode *phi = Builder.CreatePHI(lhs->getPointer()->getType(),
-                                           2, "cond-lvalue");
-    phi->addIncoming(lhs->getPointer(), lhsBlock);
-    phi->addIncoming(rhs->getPointer(), rhsBlock);
+    llvm::Value *lhsPtr = lhs->getPointer();
+    llvm::Value *rhsPtr = rhs->getPointer();
+    if (rhsPtr->getType() != lhsPtr->getType()) {
+      if (!getLangOpts().SYCLIsDevice)
+        llvm_unreachable(
+            "Unable to find a common address space for two pointers.");
+
+      auto CastToAS = [](llvm::Value *V, llvm::BasicBlock *BB, unsigned AS) {
+        auto *Ty = cast<llvm::PointerType>(V->getType());
+        if (Ty->getAddressSpace() == AS)
+          return V;
+        llvm::IRBuilder<> Builder(BB->getTerminator());
+        auto *TyAS = llvm::PointerType::get(Ty->getElementType(), AS);
+        return Builder.CreatePointerBitCastOrAddrSpaceCast(V, TyAS);
+      };
+
+      // Language rules define if it is legal to cast from one address space
+      // to another, and which address space we should use as a "common
+      // denominator". In SYCL, generic address space overlaps with all other
+      // address spaces.
+      unsigned GenericAS =
+          getContext().getTargetAddressSpace(LangAS::opencl_generic);
+
+      lhsPtr = CastToAS(lhsPtr, lhsBlock, GenericAS);
+      rhsPtr = CastToAS(rhsPtr, rhsBlock, GenericAS);
+    }
+    llvm::PHINode *phi = Builder.CreatePHI(lhsPtr->getType(), 2, "cond-lvalue");
+    phi->addIncoming(lhsPtr, lhsBlock);
+    phi->addIncoming(rhsPtr, rhsBlock);
     Address result(phi, std::min(lhs->getAlignment(), rhs->getAlignment()));
     AlignmentSource alignSource =
       std::max(lhs->getBaseInfo().getAlignmentSource(),

clang/test/CodeGenSYCL/address-space-cond-op.cpp

@@ -0,0 +1,37 @@
+// RUN: %clang_cc1 -x c++ -triple spir64-unknown-linux-sycldevice -std=c++11 -disable-llvm-passes -fsycl-is-device -emit-llvm %s -o - | FileCheck %s
+
+// CHECK: [[STYPE:%.+]] = type { i16 }
+struct S {
+  unsigned short x;
+};
+
+S foo(bool cond, S &lhs, S rhs) {
+// CHECK-LABEL:@_Z3foobR1SS_
+// CHECK:   br i1 {{.+}}, label %[[BTRUE:.+]], label %[[BFALSE:.+]]
+//
+// CHECK: [[BTRUE]]:
+// CHECK:   %[[LHS:.+]] = load [[STYPE]] addrspace(4)*, [[STYPE]] addrspace(4)**
+// CHECK:   br label %[[BEND:.+]]
+//
+// CHECK: [[BFALSE]]:
+// CHECK:   %[[RHS:.+]] = addrspacecast [[STYPE]]* {{.+}} to [[STYPE]] addrspace(4)*
+// CHECK:   br label %[[BEND]]
+//
+// CHECK: [[BEND]]:
+// CHECK:   %{{.+}} = phi [[STYPE]] addrspace(4)* [ %[[LHS]], %[[BTRUE]] ], [ %[[RHS]], %[[BFALSE]] ]
+  S val = cond ? lhs : rhs;
+  return val;
+}
+
+template <typename name, typename Func>
+__attribute__((sycl_kernel)) void kernel(Func kernelFunc) {
+  kernelFunc();
+}
+
+int main() {
+  kernel<class fake_kernel>([]() {
+    S lhs, rhs;
+    foo(true, lhs, rhs);
+  });
+  return 0;
+}