[clang] [llvm] [Clang][OpenMP] Support for dispatch construct (Sema & Codegen) support (PR #131838)

[via cfe-commits]

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@@ -4529,6 +4529,191 @@ void CodeGenFunction::EmitOMPMasterDirective(const OMPMasterDirective &S) {
   emitMaster(*this, S);
 }
 
+static Expr *replaceWithNewTraitsOrDirectCall(CapturedDecl *CDecl,
+                                              Expr *NewExpr) {
+  Expr *CurrentCallExpr = nullptr;
+  Stmt *CallExprStmt = CDecl->getBody();
+
+  if (BinaryOperator *BinaryCopyOpr = dyn_cast<BinaryOperator>(CallExprStmt)) {
+    CurrentCallExpr = BinaryCopyOpr->getRHS();
+    BinaryCopyOpr->setRHS(NewExpr);
+  } else {
+    CurrentCallExpr = dyn_cast<Expr>(CallExprStmt);
+    CDecl->setBody(NewExpr);
+  }
+
+  return CurrentCallExpr;
+}
+
+static Expr *transformCallInStmt(Stmt *StmtP, bool NoContext = false) {
+  Expr *CurrentExpr = nullptr;
+  if (auto *CptStmt = dyn_cast<CapturedStmt>(StmtP)) {
+    CapturedDecl *CDecl = CptStmt->getCapturedDecl();
+
+    CallExpr *NewCallExpr = nullptr;
+    for (const auto *attr : CDecl->attrs()) {
+      if (NoContext) {
+        if (const auto *annotateAttr =
+                llvm::dyn_cast<clang::AnnotateAttr>(attr);
+            annotateAttr && annotateAttr->getAnnotation() == "NoContextAttr") {
+          NewCallExpr = llvm::dyn_cast<CallExpr>(*annotateAttr->args_begin());
+        }
+      } else {
+        if (const auto *annotateAttr =
+                llvm::dyn_cast<clang::AnnotateAttr>(attr);
+            annotateAttr && annotateAttr->getAnnotation() == "NoVariantsAttr") {
+          NewCallExpr = llvm::dyn_cast<CallExpr>(*annotateAttr->args_begin());
+        }
+      }
+    }
+
+    CurrentExpr = replaceWithNewTraitsOrDirectCall(CDecl, NewCallExpr);
+  }
+  return CurrentExpr;
+}
+
+// emitIfElse is used for the following conditions:
+//
+// NoVariants = 0 && NoContext = 1
+//   if (Condition_NoContext) {
+//     foo_variant2(); // Present in AnnotationAttr
+//   } else {
+//     foo_variant();
+//   }
+//
+// NoVariants = 1 && NoContext = 0
+//   if (Condition_NoVariants) {
+//     foo();
+//   } else {
+//     foo_variant();
+//   }
+//
+// NoVariants = 1 && NoContext = 1
+//   if (Condition_NoVariants) {   // ==> label if.then.NoVariants
+//     foo();
+//   } else {  // ==> label else.NoVariants
+//     if (Condition_NoContext) {   // ==> label if.then.NoContext
+//       foo_variant2(); // Present in AnnotationAttr
+//     } else {   // ==> label else
+//       foo_variant();
+//     }
+//   }
+//
+static void emitIfElse(CodeGenFunction *CGF, Stmt *AssociatedStmt,
----------------
SunilKuravinakop wrote:

Do you have an example of constructors/destructors where it will not work? The codegen for the `nocontext` & `novariant` clauses occurring together is present in the lit test case.  I have written the code according to truth table mentioned by  Deepak:
```
novariants(0), nocontext(0): Allow selective variant substitution according to context match
novariants(0), nocontext(1): Allow selective variant substitution according to context match (NO MATCH
                             for selectors that require **dispatch** trait)
novariants(1), nocontext(0): Always call the base function (shuts off any variant substitution for the call)
novariants(1), nocontext(1): Always call the base function (shuts off any variant substitution for the call)
```


https://github.com/llvm/llvm-project/pull/131838