[OpenMP][IR-Builder] Introduce the finalization stack
As a permanent and generic solution to the problem of variable
finalization (destructors, lastprivate, ...), this patch introduces the
finalization stack. The objects on the stack describe (1) the
(structured) regions the OpenMP-IR-Builder is currently constructing,
(2) if these are cancellable, and (3) the callback that will perform the
finalization (=cleanup) when necessary.
As the finalization can be necessary multiple times, at different source
locations, the callback takes the position at which code is currently
generated. This position will also encode the destination of the "region
exit" block *iff* the finalization call was issues for a region
generated by the OpenMPIRBuilder. For regions generated through the old
Clang OpenMP code geneneration, the "region exit" is determined by Clang
inside the finalization call instead (see getOMPCancelDestination).
As a first user, the parallel + cancel barrier interaction is changed.
In contrast to the temporary solution before, the barrier generation in
Clang does not need to be aware of the "CancelDestination" block.
Instead, the finalization callback is and, as described above, later
even that one does not need to be.
D70109 will be updated to use this scheme.
Reviewed By: ABataev
Differential Revision: https://reviews.llvm.org/D70258
diff --git a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
index 1373339..4c173e0 100644
--- a/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
+++ b/llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
@@ -205,7 +205,8 @@
// If we are in a cancellable parallel region, barriers are cancellation
// points.
// TODO: Check why we would force simple calls or to ignore the cancel flag.
- bool UseCancelBarrier = !ForceSimpleCall && CancellationBlock;
+ bool UseCancelBarrier =
+ !ForceSimpleCall && isLastFinalizationInfoCancellable(OMPD_parallel);
Value *Result = Builder.CreateCall(
getOrCreateRuntimeFunction(UseCancelBarrier ? OMPRTL___kmpc_cancel_barrier
@@ -217,19 +218,22 @@
BasicBlock *BB = Builder.GetInsertBlock();
BasicBlock *NonCancellationBlock = BasicBlock::Create(
BB->getContext(), BB->getName() + ".cont", BB->getParent());
+ BasicBlock *CancellationBlock = BasicBlock::Create(
+ BB->getContext(), BB->getName() + ".cncl", BB->getParent());
// Jump to them based on the return value.
Value *Cmp = Builder.CreateIsNull(Result);
Builder.CreateCondBr(Cmp, NonCancellationBlock, CancellationBlock,
/* TODO weight */ nullptr, nullptr);
- Builder.SetInsertPoint(NonCancellationBlock);
- assert(CancellationBlock->getParent() == BB->getParent() &&
- "Unexpected cancellation block parent!");
+ // From the cancellation block we finalize all variables and go to the
+ // post finalization block that is known to the FiniCB callback.
+ Builder.SetInsertPoint(CancellationBlock);
+ auto &FI = FinalizationStack.back();
+ FI.FiniCB(Builder.saveIP());
- // TODO: This is a workaround for now, we always reset the cancellation
- // block until we manage it ourselves here.
- CancellationBlock = nullptr;
+ // The continuation block is where code generation continues.
+ Builder.SetInsertPoint(NonCancellationBlock);
}
return Builder.saveIP();