[Acc] Do not statically dispatch into IslNodeBuilder's createFor

Summary:
When GPUNodeBuilder creates loops inside the kernel, it dispatches to
IslNodeBuilder. This however is surprisingly dangerous, since it accesses the
AST Node's user through the wrong type. This patch fixes this problem by
overriding createFor correctly.

This fixes PR35010.

Reviewers: grosser, bollu, Meinersbur

Reviewed By: Meinersbur

Subscribers: Meinersbur, nemanjai, pollydev, llvm-commits, kbarton

Differential Revision: https://reviews.llvm.org/D39364

llvm-svn: 316872

polly/include/polly/CodeGen/IslNodeBuilder.h

@@ -351,7 +351,7 @@ class IslNodeBuilder {
   bool preloadInvariantEquivClass(InvariantEquivClassTy &IAClass);
 
   void createForVector(__isl_take isl_ast_node *For, int VectorWidth);
-  void createForSequential(__isl_take isl_ast_node *For, bool KnownParallel);
+  void createForSequential(__isl_take isl_ast_node *For, bool MarkParallel);
 
   /// Create LLVM-IR that executes a for node thread parallel.
   ///

polly/lib/CodeGen/IslNodeBuilder.cpp

@@ -530,7 +530,7 @@ static bool IsLoopVectorizerDisabled(isl::ast_node Node) {
 }
 
 void IslNodeBuilder::createForSequential(__isl_take isl_ast_node *For,
-                                         bool KnownParallel) {
+                                         bool MarkParallel) {
   isl_ast_node *Body;
   isl_ast_expr *Init, *Inc, *Iterator, *UB;
   isl_id *IteratorID;
@@ -539,10 +539,6 @@ void IslNodeBuilder::createForSequential(__isl_take isl_ast_node *For,
   BasicBlock *ExitBlock;
   Value *IV;
   CmpInst::Predicate Predicate;
-  bool Parallel;
-
-  Parallel = KnownParallel || (IslAstInfo::isParallel(For) &&
-                               !IslAstInfo::isReductionParallel(For));
 
   bool LoopVectorizerDisabled =
       IsLoopVectorizerDisabled(isl::manage(isl_ast_node_copy(For)));
@@ -582,13 +578,13 @@ void IslNodeBuilder::createForSequential(__isl_take isl_ast_node *For,
   bool UseGuardBB =
       !SE.isKnownPredicate(Predicate, SE.getSCEV(ValueLB), SE.getSCEV(ValueUB));
   IV = createLoop(ValueLB, ValueUB, ValueInc, Builder, LI, DT, ExitBlock,
-                  Predicate, &Annotator, Parallel, UseGuardBB,
+                  Predicate, &Annotator, MarkParallel, UseGuardBB,
                   LoopVectorizerDisabled);
   IDToValue[IteratorID] = IV;
 
   create(Body);
 
-  Annotator.popLoop(Parallel);
+  Annotator.popLoop(MarkParallel);
 
   IDToValue.erase(IDToValue.find(IteratorID));
 
@@ -795,7 +791,9 @@ void IslNodeBuilder::createFor(__isl_take isl_ast_node *For) {
     createForParallel(For);
     return;
   }
-  createForSequential(For, false);
+  bool Parallel =
+      (IslAstInfo::isParallel(For) && !IslAstInfo::isReductionParallel(For));
+  createForSequential(For, Parallel);
 }
 
 void IslNodeBuilder::createIf(__isl_take isl_ast_node *If) {

polly/lib/CodeGen/PPCGCodeGeneration.cpp

@@ -415,6 +415,8 @@ class GPUNodeBuilder : public IslNodeBuilder {
   /// @param UserStmt The ast node to generate code for.
   virtual void createUser(__isl_take isl_ast_node *UserStmt);
 
+  virtual void createFor(__isl_take isl_ast_node *Node);
+
   enum DataDirection { HOST_TO_DEVICE, DEVICE_TO_HOST };
 
   /// Create code for a data transfer statement
@@ -1286,6 +1288,11 @@ void GPUNodeBuilder::createUser(__isl_take isl_ast_node *UserStmt) {
   isl_ast_node_free(UserStmt);
   return;
 }
+
+void GPUNodeBuilder::createFor(__isl_take isl_ast_node *Node) {
+  createForSequential(Node, false);
+}
+
 void GPUNodeBuilder::createKernelCopy(ppcg_kernel_stmt *KernelStmt) {
   isl_ast_expr *LocalIndex = isl_ast_expr_copy(KernelStmt->u.c.local_index);
   LocalIndex = isl_ast_expr_address_of(LocalIndex);