[OpenMP] Reapply rL256842: [OpenMP] Offloading descriptor registration and device codegen.

This patch attempts to fix the regressions identified when the patch was committed initially. 

Thanks to Michael Liao for identifying the fix in the offloading metadata generation 
related with side effects in evaluation of function arguments. 
 

llvm-svn: 256933

1 files changed, 30 insertions, 9 deletions

diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index 82011984f8e..14917c20c53 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -2571,14 +2571,8 @@ void CodeGenFunction::EmitOMPTargetDirective(const OMPTargetDirective &S) {
   llvm::SmallVector<llvm::Value *, 16> CapturedVars;
   GenerateOpenMPCapturedVars(CS, CapturedVars);
 
-  // Emit target region as a standalone region.
-  auto &&CodeGen = [&CS](CodeGenFunction &CGF) {
-    CGF.EmitStmt(CS.getCapturedStmt());
-  };
-
-  // Obtain the target region outlined function.
-  llvm::Value *Fn =
-      CGM.getOpenMPRuntime().emitTargetOutlinedFunction(S, CodeGen);
+  llvm::Function *Fn = nullptr;
+  llvm::Constant *FnID = nullptr;
 
   // Check if we have any if clause associated with the directive.
   const Expr *IfCond = nullptr;
@@ -2593,7 +2587,34 @@ void CodeGenFunction::EmitOMPTargetDirective(const OMPTargetDirective &S) {
     Device = C->getDevice();
   }
 
-  CGM.getOpenMPRuntime().emitTargetCall(*this, S, Fn, IfCond, Device,
+  // Check if we have an if clause whose conditional always evaluates to false
+  // or if we do not have any targets specified. If so the target region is not
+  // an offload entry point.
+  bool IsOffloadEntry = true;
+  if (IfCond) {
+    bool Val;
+    if (ConstantFoldsToSimpleInteger(IfCond, Val) && !Val)
+      IsOffloadEntry = false;
+  }
+  if (CGM.getLangOpts().OMPTargetTriples.empty())
+    IsOffloadEntry = false;
+
+  assert(CurFuncDecl && "No parent declaration for target region!");
+  StringRef ParentName;
+  // In case we have Ctors/Dtors we use the complete type variant to produce
+  // the mangling of the device outlined kernel.
+  if (auto *D = dyn_cast<CXXConstructorDecl>(CurFuncDecl))
+    ParentName = CGM.getMangledName(GlobalDecl(D, Ctor_Complete));
+  else if (auto *D = dyn_cast<CXXDestructorDecl>(CurFuncDecl))
+    ParentName = CGM.getMangledName(GlobalDecl(D, Dtor_Complete));
+  else
+    ParentName =
+        CGM.getMangledName(GlobalDecl(cast<FunctionDecl>(CurFuncDecl)));
+
+  CGM.getOpenMPRuntime().emitTargetOutlinedFunction(S, ParentName, Fn, FnID,
+                                                    IsOffloadEntry);
+
+  CGM.getOpenMPRuntime().emitTargetCall(*this, S, Fn, FnID, IfCond, Device,
                                         CapturedVars);
 }