[OPENMP]Reduce calls for the mangled names.

Use canonical decls instead of mangled names in the set of already
emitted decls. This allows to reduce the number of function calls for
getting declarations mangled names and speedup the compilation.

Author: alexey-bataev

clang/lib/CodeGen/CGOpenMPRuntime.cpp

@@ -9659,9 +9659,9 @@ bool CGOpenMPRuntime::emitTargetFunctions(GlobalDecl GD) {
   }
 
   const ValueDecl *VD = cast<ValueDecl>(GD.getDecl());
-  StringRef Name = CGM.getMangledName(GD);
   // Try to detect target regions in the function.
   if (const auto *FD = dyn_cast<FunctionDecl>(VD)) {
+    StringRef Name = CGM.getMangledName(GD);
     scanForTargetRegionsFunctions(FD->getBody(), Name);
     Optional<OMPDeclareTargetDeclAttr::DevTypeTy> DevTy =
         OMPDeclareTargetDeclAttr::getDeviceType(FD);
@@ -9672,7 +9672,7 @@ bool CGOpenMPRuntime::emitTargetFunctions(GlobalDecl GD) {
 
   // Do not to emit function if it is not marked as declare target.
   return !OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(VD) &&
-         AlreadyEmittedTargetFunctions.count(Name) == 0;
+         AlreadyEmittedTargetDecls.count(VD) == 0;
 }
 
 bool CGOpenMPRuntime::emitTargetGlobalVariable(GlobalDecl GD) {
@@ -9903,20 +9903,20 @@ bool CGOpenMPRuntime::markAsGlobalTarget(GlobalDecl GD) {
   if (!CGM.getLangOpts().OpenMPIsDevice || !ShouldMarkAsGlobal)
     return true;
 
-  StringRef Name = CGM.getMangledName(GD);
   const auto *D = cast<FunctionDecl>(GD.getDecl());
   // Do not to emit function if it is marked as declare target as it was already
   // emitted.
   if (OMPDeclareTargetDeclAttr::isDeclareTargetDeclaration(D)) {
-    if (D->hasBody() && AlreadyEmittedTargetFunctions.count(Name) == 0) {
-      if (auto *F = dyn_cast_or_null<llvm::Function>(CGM.GetGlobalValue(Name)))
+    if (D->hasBody() && AlreadyEmittedTargetDecls.count(D) == 0) {
+      if (auto *F = dyn_cast_or_null<llvm::Function>(
+              CGM.GetGlobalValue(CGM.getMangledName(GD))))
         return !F->isDeclaration();
       return false;
     }
     return true;
   }
 
-  return !AlreadyEmittedTargetFunctions.insert(Name).second;
+  return !AlreadyEmittedTargetDecls.insert(D).second;
 }
 
 llvm::Function *CGOpenMPRuntime::emitRequiresDirectiveRegFun() {

clang/lib/CodeGen/CGOpenMPRuntime.h

@@ -20,6 +20,7 @@
 #include "clang/Basic/OpenMPKinds.h"
 #include "clang/Basic/SourceLocation.h"
 #include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/Frontend/OpenMP/OMPConstants.h"
@@ -672,8 +673,8 @@ class CGOpenMPRuntime {
   OffloadEntriesInfoManagerTy OffloadEntriesInfoManager;
 
   bool ShouldMarkAsGlobal = true;
-  /// List of the emitted functions.
-  llvm::StringSet<> AlreadyEmittedTargetFunctions;
+  /// List of the emitted declarations.
+  llvm::DenseSet<CanonicalDeclPtr<const Decl>> AlreadyEmittedTargetDecls;
   /// List of the global variables with their addresses that should not be
   /// emitted for the target.
   llvm::StringMap<llvm::WeakTrackingVH> EmittedNonTargetVariables;