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

This patch adds the CodeGen changes needed for enabling HIP parallel algorithm offload on AMDGPU targets. This change relaxes restrictions on what gets emitted on the device path, when compiling in `hipstdpar` mode:

1. Unless a function is explicitly marked `__host__`, it will get emitted, whereas before only `__device__` and `__global__` functions would be emitted;
2. Unsupported builtins are ignored as opposed to being marked as an error, as the decision on their validity is deferred to the `hipstdpar` specific code selection pass;
3. We add a `hipstdpar` specific pass to the opt pipeline, independent of optimisation level:
    - When compiling for the host, iff the user requested it via the `--hipstdpar-interpose-alloc` flag, we add a pass which replaces canonical allocation / deallocation functions with accelerator aware equivalents.

A test to validate that unannotated functions get correctly emitted is added as well.

Reviewed by: yaxunl, efriedma

Differential Revision: https://reviews.llvm.org/D155850

1 files changed, 9 insertions, 3 deletions

diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 4277719..3682a2c 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -2594,10 +2594,15 @@ void CodeGenFunction::checkTargetFeatures(SourceLocation Loc,
   std::string MissingFeature;
   llvm::StringMap<bool> CallerFeatureMap;
   CGM.getContext().getFunctionFeatureMap(CallerFeatureMap, FD);
+  // When compiling in HipStdPar mode we have to be conservative in rejecting
+  // target specific features in the FE, and defer the possible error to the
+  // AcceleratorCodeSelection pass, wherein iff an unsupported target builtin is
+  // referenced by an accelerator executable function, we emit an error.
+  bool IsHipStdPar = getLangOpts().HIPStdPar && getLangOpts().CUDAIsDevice;
   if (BuiltinID) {
     StringRef FeatureList(CGM.getContext().BuiltinInfo.getRequiredFeatures(BuiltinID));
     if (!Builtin::evaluateRequiredTargetFeatures(
-        FeatureList, CallerFeatureMap)) {
+        FeatureList, CallerFeatureMap) && !IsHipStdPar) {
       CGM.getDiags().Report(Loc, diag::err_builtin_needs_feature)
           << TargetDecl->getDeclName()
           << FeatureList;
@@ -2630,7 +2635,7 @@ void CodeGenFunction::checkTargetFeatures(SourceLocation Loc,
         return false;
       }
       return true;
-    }))
+    }) && !IsHipStdPar)
       CGM.getDiags().Report(Loc, diag::err_function_needs_feature)
           << FD->getDeclName() << TargetDecl->getDeclName() << MissingFeature;
   } else if (!FD->isMultiVersion() && FD->hasAttr<TargetAttr>()) {
@@ -2639,7 +2644,8 @@ void CodeGenFunction::checkTargetFeatures(SourceLocation Loc,
 
     for (const auto &F : CalleeFeatureMap) {
       if (F.getValue() && (!CallerFeatureMap.lookup(F.getKey()) ||
-                           !CallerFeatureMap.find(F.getKey())->getValue()))
+                           !CallerFeatureMap.find(F.getKey())->getValue()) &&
+          !IsHipStdPar)
         CGM.getDiags().Report(Loc, diag::err_function_needs_feature)
             << FD->getDeclName() << TargetDecl->getDeclName() << F.getKey();
     }