[OpenMP] Refactor code that calls codegen for target regions on the device.

[arpith-jacob]

Summary

This patch refactors code that calls codegen for target regions. Currently
the codebase only supports the 'target' directive. The patch pulls out
common target processing code into a static function that can be called
by codegen for any target directive.

[ABataev]

Is this an NFC patch? If so add 'NFC' to this patch.
LG

[arpith-jacob]

Thanks Alexey.

Is this an NFC patch? If so add 'NFC' to this patch.

Do you mean NVPTX? No, this is a patch to support target directives for any accelerator.

cfe/trunk/lib/CodeGen/CGOpenMPRuntime.cpp

void CGOpenMPRuntime::emitTargetCall(CodeGenFunction &CGF,
   CGF.EmitBlock(OffloadContBlock, /*IsFinished=*/true);
 }
 
 void CGOpenMPRuntime::scanForTargetRegionsFunctions(const Stmt *S,
                                                     StringRef ParentName) {
   if (!S)
     return;
 
-  // If we find a OMP target directive, codegen the outline function and
-  // register the result.
-  // FIXME: Add other directives with target when they become supported.
-  bool isTargetDirective = isa<OMPTargetDirective>(S);
+  // Codegen OMP target directives that offload compute to the device.
+  bool requiresDeviceCodegen =
+      isa<OMPExecutableDirective>(S) &&
+      isOpenMPTargetExecutionDirective(
+          cast<OMPExecutableDirective>(S)->getDirectiveKind());
 
-  if (isTargetDirective) {
-    auto *E = cast<OMPExecutableDirective>(S);
+  if (requiresDeviceCodegen) {
+    auto &E = *cast<OMPExecutableDirective>(S);
     unsigned DeviceID;
     unsigned FileID;
     unsigned Line;
-    getTargetEntryUniqueInfo(CGM.getContext(), E->getLocStart(), DeviceID,
+    getTargetEntryUniqueInfo(CGM.getContext(), E.getLocStart(), DeviceID,
                              FileID, Line);
 
     // Is this a target region that should not be emitted as an entry point? If
     // so just signal we are done with this target region.
     if (!OffloadEntriesInfoManager.hasTargetRegionEntryInfo(DeviceID, FileID,
                                                             ParentName, Line))
       return;
 
-    llvm::Function *Fn;
-    llvm::Constant *Addr;
-    std::tie(Fn, Addr) =
-        CodeGenFunction::EmitOMPTargetDirectiveOutlinedFunction(
-            CGM, cast<OMPTargetDirective>(*E), ParentName,
-            /*isOffloadEntry=*/true);
-    assert(Fn && Addr && "Target region emission failed.");
+    switch (S->getStmtClass()) {
+    case Stmt::OMPTargetDirectiveClass:
+      CodeGenFunction::EmitOMPTargetDeviceFunction(
+          CGM, ParentName, cast<OMPTargetDirective>(*S));
+      break;
+    default:
+      llvm_unreachable("Unknown target directive for OpenMP device codegen.");
+    }
     return;
   }
 
   if (const OMPExecutableDirective *E = dyn_cast<OMPExecutableDirective>(S)) {
     if (!E->hasAssociatedStmt())
       return;
 
     scanForTargetRegionsFunctions(

cfe/trunk/lib/CodeGen/CGStmtOpenMP.cpp

auto &&CodeGen = [&S, Kind, IsSeqCst, CS](CodeGenFunction &CGF,
     EmitOMPAtomicExpr(CGF, Kind, IsSeqCst, S.isPostfixUpdate(), S.getX(),
                       S.getV(), S.getExpr(), S.getUpdateExpr(),
                       S.isXLHSInRHSPart(), S.getLocStart());
   };
   OMPLexicalScope Scope(*this, S, /*AsInlined=*/true);
   CGM.getOpenMPRuntime().emitInlinedDirective(*this, OMPD_atomic, CodeGen);
 }
 
-std::pair<llvm::Function * /*OutlinedFn*/, llvm::Constant * /*OutlinedFnID*/>
-CodeGenFunction::EmitOMPTargetDirectiveOutlinedFunction(
-    CodeGenModule &CGM, const OMPTargetDirective &S, StringRef ParentName,
-    bool IsOffloadEntry) {
-  llvm::Function *OutlinedFn = nullptr;
-  llvm::Constant *OutlinedFnID = nullptr;
-  auto &&CodeGen = [&S](CodeGenFunction &CGF, PrePostActionTy &Action) {
-    OMPPrivateScope PrivateScope(CGF);
-    (void)CGF.EmitOMPFirstprivateClause(S, PrivateScope);
-    CGF.EmitOMPPrivateClause(S, PrivateScope);
-    (void)PrivateScope.Privatize();
-
-    Action.Enter(CGF);
-    CGF.EmitStmt(cast<CapturedStmt>(S.getAssociatedStmt())->getCapturedStmt());
-  };
-  // Emit target region as a standalone region.
-  CGM.getOpenMPRuntime().emitTargetOutlinedFunction(
-      S, ParentName, OutlinedFn, OutlinedFnID, IsOffloadEntry, CodeGen);
-  return std::make_pair(OutlinedFn, OutlinedFnID);
-}
-
-void CodeGenFunction::EmitOMPTargetDirective(const OMPTargetDirective &S) {
+static void emitCommonOMPTargetDirective(CodeGenFunction &CGF,
+                                         const OMPExecutableDirective &S,
+                                         const RegionCodeGenTy &CodeGen) {
+  assert(isOpenMPTargetExecutionDirective(S.getDirectiveKind()));
+  CodeGenModule &CGM = CGF.CGM;
   const CapturedStmt &CS = *cast<CapturedStmt>(S.getAssociatedStmt());
 
   llvm::SmallVector<llvm::Value *, 16> CapturedVars;
-  GenerateOpenMPCapturedVars(CS, CapturedVars);
+  CGF.GenerateOpenMPCapturedVars(CS, CapturedVars);
 
   llvm::Function *Fn = nullptr;
   llvm::Constant *FnID = nullptr;
 
   // Check if we have any if clause associated with the directive.
   const Expr *IfCond = nullptr;
 
   if (auto *C = S.getSingleClause<OMPIfClause>()) {
     IfCond = C->getCondition();
   }
 
   // Check if we have any device clause associated with the directive.
   const Expr *Device = nullptr;
   if (auto *C = S.getSingleClause<OMPDeviceClause>()) {
     Device = C->getDevice();
   }
 
   // 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)
+    if (CGF.ConstantFoldsToSimpleInteger(IfCond, Val) && !Val)
       IsOffloadEntry = false;
   }
   if (CGM.getLangOpts().OMPTargetTriples.empty())
     IsOffloadEntry = false;
 
-  assert(CurFuncDecl && "No parent declaration for target region!");
+  assert(CGF.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))
+  if (auto *D = dyn_cast<CXXConstructorDecl>(CGF.CurFuncDecl))
     ParentName = CGM.getMangledName(GlobalDecl(D, Ctor_Complete));
-  else if (auto *D = dyn_cast<CXXDestructorDecl>(CurFuncDecl))
+  else if (auto *D = dyn_cast<CXXDestructorDecl>(CGF.CurFuncDecl))
     ParentName = CGM.getMangledName(GlobalDecl(D, Dtor_Complete));
   else
     ParentName =
-        CGM.getMangledName(GlobalDecl(cast<FunctionDecl>(CurFuncDecl)));
+        CGM.getMangledName(GlobalDecl(cast<FunctionDecl>(CGF.CurFuncDecl)));
 
-  std::tie(Fn, FnID) = EmitOMPTargetDirectiveOutlinedFunction(
-      CGM, S, ParentName, IsOffloadEntry);
-  OMPLexicalScope Scope(*this, S);
-  CGM.getOpenMPRuntime().emitTargetCall(*this, S, Fn, FnID, IfCond, Device,
+  // Emit target region as a standalone region.
+  CGM.getOpenMPRuntime().emitTargetOutlinedFunction(S, ParentName, Fn, FnID,
+                                                    IsOffloadEntry, CodeGen);
+  OMPLexicalScope Scope(CGF, S);
+  CGM.getOpenMPRuntime().emitTargetCall(CGF, S, Fn, FnID, IfCond, Device,
                                         CapturedVars);
 }
 
+static void emitTargetRegion(CodeGenFunction &CGF, const OMPTargetDirective &S,
+                             PrePostActionTy &Action) {
+  CodeGenFunction::OMPPrivateScope PrivateScope(CGF);
+  (void)CGF.EmitOMPFirstprivateClause(S, PrivateScope);
+  CGF.EmitOMPPrivateClause(S, PrivateScope);
+  (void)PrivateScope.Privatize();
+
+  Action.Enter(CGF);
+  CGF.EmitStmt(cast<CapturedStmt>(S.getAssociatedStmt())->getCapturedStmt());
+}
+
+void CodeGenFunction::EmitOMPTargetDeviceFunction(CodeGenModule &CGM,
+                                                  StringRef ParentName,
+                                                  const OMPTargetDirective &S) {
+  auto &&CodeGen = [&S](CodeGenFunction &CGF, PrePostActionTy &Action) {
+    emitTargetRegion(CGF, S, Action);
+  };
+  llvm::Function *Fn;
+  llvm::Constant *Addr;
+  // Emit target region as a standalone region.
+  CGM.getOpenMPRuntime().emitTargetOutlinedFunction(
+      S, ParentName, Fn, Addr, /*IsOffloadEntry=*/true, CodeGen);
+  assert(Fn && Addr && "Target device function emission failed.");
+}
+
+void CodeGenFunction::EmitOMPTargetDirective(const OMPTargetDirective &S) {
+  auto &&CodeGen = [&S](CodeGenFunction &CGF, PrePostActionTy &Action) {
+    emitTargetRegion(CGF, S, Action);
+  };
+  emitCommonOMPTargetDirective(*this, S, CodeGen);
+}
+
 static void emitCommonOMPTeamsDirective(CodeGenFunction &CGF,
                                         const OMPExecutableDirective &S,
                                         OpenMPDirectiveKind InnermostKind,
                                         const RegionCodeGenTy &CodeGen) {
   auto CS = cast<CapturedStmt>(S.getAssociatedStmt());
   auto OutlinedFn = CGF.CGM.getOpenMPRuntime().
       emitParallelOrTeamsOutlinedFunction(S,
           *CS->getCapturedDecl()->param_begin(), InnermostKind, CodeGen);

cfe/trunk/lib/CodeGen/CodeGenFunction.h

void EmitOMPTargetTeamsDistributeDirective(
       const OMPTargetTeamsDistributeDirective &S);
   void EmitOMPTargetTeamsDistributeParallelForDirective(
       const OMPTargetTeamsDistributeParallelForDirective &S);
   void EmitOMPTargetTeamsDistributeParallelForSimdDirective(
       const OMPTargetTeamsDistributeParallelForSimdDirective &S);
   void EmitOMPTargetTeamsDistributeSimdDirective(
       const OMPTargetTeamsDistributeSimdDirective &S);
 
-  /// Emit outlined function for the target directive.
-  static std::pair<llvm::Function * /*OutlinedFn*/,
-                   llvm::Constant * /*OutlinedFnID*/>
-  EmitOMPTargetDirectiveOutlinedFunction(CodeGenModule &CGM,
-                                         const OMPTargetDirective &S,
+  /// Emit device code for the target directive.
+  static void EmitOMPTargetDeviceFunction(CodeGenModule &CGM,
                                           StringRef ParentName,
-                                         bool IsOffloadEntry);
+                                          const OMPTargetDirective &S);
   /// \brief Emit inner loop of the worksharing/simd construct.
   ///
   /// \param S Directive, for which the inner loop must be emitted.
   /// \param RequiresCleanup true, if directive has some associated private
   /// variables.
   /// \param LoopCond Bollean condition for loop continuation.
   /// \param IncExpr Increment expression for loop control variable.
   /// \param BodyGen Generator for the inner body of the inner loop.