[HIP] Warn capture this pointer in device lambda

HIP currently diagnose capture of this pointer in device lambda in
host member functions. If this pointer points to managed memory,
it can be used in both device and host functions. Under this
situation, capturing this pointer in device lambda functions
in host member functions is valid usage. Change the diagnostic
about capturing this pointer to warning.

Reviewed by: Artem Belevich

Differential Revision: https://reviews.llvm.org/D108493

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -8391,8 +8391,10 @@ def err_ref_bad_target_global_initializer : Error<
   "function %1 in global initializer">;
 def err_capture_bad_target : Error<
   "capture host variable %0 by reference in device or host device lambda function">;
-def err_capture_bad_target_this_ptr : Error<
-  "capture host side class data member by this pointer in device or host device lambda function">;
+def warn_maybe_capture_bad_target_this_ptr : Warning<
+  "capture host side class data member by this pointer in device or host device lambda function "
+  "may result in invalid memory access if this pointer is not accessible on device side">,
+  InGroup<DiagGroup<"gpu-maybe-wrong-side">>;
 def warn_kern_is_method : Extension<
   "kernel function %0 is a member function; this may not be accepted by nvcc">,
   InGroup<CudaCompat>;

clang/lib/Sema/SemaCUDA.cpp

@@ -878,8 +878,13 @@ void Sema::CUDACheckLambdaCapture(CXXMethodDecl *Callee,
                           diag::err_capture_bad_target, Callee, *this)
         << Capture.getVariable();
   } else if (Capture.isThisCapture()) {
+    // Capture of this pointer is allowed since this pointer may be pointing to
+    // managed memory which is accessible on both device and host sides. It only
+    // results in invalid memory access if this pointer points to memory not
+    // accessible on device side.
     SemaDiagnosticBuilder(DiagKind, Capture.getLocation(),
-                          diag::err_capture_bad_target_this_ptr, Callee, *this);
+                          diag::warn_maybe_capture_bad_target_this_ptr, Callee,
+                          *this);
   }
   return;
 }

clang/test/SemaCUDA/lambda.cu

@@ -1,13 +1,18 @@
 // RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify=com %s
-// RUN: %clang_cc1 -std=c++17 -fsyntax-only -fcuda-is-device -verify=com,dev %s
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -fcuda-is-device -verify=com,dev,warn %s
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -fcuda-is-device -verify=com,dev,warn \
+// RUN:   -triple amdgcn-amd-amdhsa -target-cpu gfx906 -x hip %s
+// RUN: %clang_cc1 -std=c++17 -fsyntax-only -fcuda-is-device -verify=com,dev \
+// RUN:   -Wno-gpu-maybe-wrong-side %s
 
 #include "Inputs/cuda.h"
 
 auto global_lambda = [] () { return 123; };
 
 template<class F>
 __global__ void kernel(F f) { f(); }
-// dev-note@-1 7{{called by 'kernel<(lambda}}
+// dev-note@-1 3{{called by 'kernel<(lambda}}
+// warn-note@-2 5{{called by 'kernel<(lambda}}
 
 __host__ __device__ void hd(int x);
 
@@ -22,19 +27,23 @@ public:
     kernel<<<1,1>>>([](){ hd(0); });
 
     kernel<<<1,1>>>([=](){ hd(b); });
-    // dev-error@-1 {{capture host side class data member by this pointer in device or host device lambda function}}
+    // warn-warning@-1 {{capture host side class data member by this pointer in device or host device lambda function may result in invalid memory access if this pointer is not accessible on device side}}
 
     kernel<<<1,1>>>([&](){ hd(b); });
-    // dev-error@-1 {{capture host side class data member by this pointer in device or host device lambda function}}
+    // warn-warning@-1 {{capture host side class data member by this pointer in device or host device lambda function may result in invalid memory access if this pointer is not accessible on device side}}
 
     kernel<<<1,1>>>([&] __device__ (){ hd(b); });
-    // dev-error@-1 {{capture host side class data member by this pointer in device or host device lambda function}}
+    // warn-warning@-1 {{capture host side class data member by this pointer in device or host device lambda function may result in invalid memory access if this pointer is not accessible on device side}}
 
     kernel<<<1,1>>>([&](){
       auto f = [&]{ hd(b); };
-      // dev-error@-1 {{capture host side class data member by this pointer in device or host device lambda function}}
+      // warn-warning@-1 {{capture host side class data member by this pointer in device or host device lambda function may result in invalid memory access if this pointer is not accessible on device side}}
       f();
     });
+
+    auto lambda1 = [this] __device__ { hd(this->b); };
+    // warn-warning@-1 {{capture host side class data member by this pointer in device or host device lambda function may result in invalid memory access if this pointer is not accessible on device side}}
+    kernel<<<1,1>>>(lambda1);
   }
 };