[HIP][Clang][Sema] Add Sema support for `hipstdpar`

This patch adds the Sema changes needed for enabling HIP parallel algorithm offload on AMDGPU targets. This change impacts the CUDA / HIP language specific checks, and only manifests if compiling in `hipstdpar` mode. In this case, we essentially do three things:

1. Allow device side callers to call host side callees - since the user visible HLL would be standard C++, with no annotations / restriction mechanisms, we cannot unambiguously establish that such a call is an error, so we conservatively allow all such calls, deferring actual cleanup to a subsequent pass over IR;
2. Allow host formed lambdas to capture by reference;
3. Allow device functions to use host global variables.

Reviewed by: yaxunl

Differential Revision: https://reviews.llvm.org/D155833

1 files changed, 10 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaCUDA.cpp b/clang/lib/Sema/SemaCUDA.cpp
index 88f5484..3336dbf 100644
--- a/clang/lib/Sema/SemaCUDA.cpp
+++ b/clang/lib/Sema/SemaCUDA.cpp
@@ -249,6 +249,15 @@ Sema::IdentifyCUDAPreference(const FunctionDecl *Caller,
       (CallerTarget == CFT_Global && CalleeTarget == CFT_Device))
     return CFP_Native;
 
+  // HipStdPar mode is special, in that assessing whether a device side call to
+  // a host target is deferred to a subsequent pass, and cannot unambiguously be
+  // adjudicated in the AST, hence we optimistically allow them to pass here.
+  if (getLangOpts().HIPStdPar &&
+      (CallerTarget == CFT_Global || CallerTarget == CFT_Device ||
+       CallerTarget == CFT_HostDevice) &&
+      CalleeTarget == CFT_Host)
+    return CFP_HostDevice;
+
   // (d) HostDevice behavior depends on compilation mode.
   if (CallerTarget == CFT_HostDevice) {
     // It's OK to call a compilation-mode matching function from an HD one.
@@ -895,7 +904,7 @@ void Sema::CUDACheckLambdaCapture(CXXMethodDecl *Callee,
   if (!ShouldCheck || !Capture.isReferenceCapture())
     return;
   auto DiagKind = SemaDiagnosticBuilder::K_Deferred;
-  if (Capture.isVariableCapture()) {
+  if (Capture.isVariableCapture() && !getLangOpts().HIPStdPar) {
     SemaDiagnosticBuilder(DiagKind, Capture.getLocation(),
                           diag::err_capture_bad_target, Callee, *this)
         << Capture.getVariable();