6024e5c395
clang 20.0.0 (based on r547379) from build 12806354. Bug: http://b/379133546 Test: N/A Change-Id: I2eb8938af55d809de674be63cb30cf27e801862b Upstream-Commit: ad834e67b1105d15ef907f6255d4c96e8e733f57
72 lines
3.2 KiB
C++
72 lines
3.2 KiB
C++
//===- PlaceSafepoints.h - Place GC Safepoints ----------------------------===//
|
|
//
|
|
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
|
|
// See https://llvm.org/LICENSE.txt for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// Place garbage collection safepoints at appropriate locations in the IR. This
|
|
// does not make relocation semantics or variable liveness explicit. That's
|
|
// done by RewriteStatepointsForGC.
|
|
//
|
|
// Terminology:
|
|
// - A call is said to be "parseable" if there is a stack map generated for the
|
|
// return PC of the call. A runtime can determine where values listed in the
|
|
// deopt arguments and (after RewriteStatepointsForGC) gc arguments are located
|
|
// on the stack when the code is suspended inside such a call. Every parse
|
|
// point is represented by a call wrapped in an gc.statepoint intrinsic.
|
|
// - A "poll" is an explicit check in the generated code to determine if the
|
|
// runtime needs the generated code to cooperate by calling a helper routine
|
|
// and thus suspending its execution at a known state. The call to the helper
|
|
// routine will be parseable. The (gc & runtime specific) logic of a poll is
|
|
// assumed to be provided in a function of the name "gc.safepoint_poll".
|
|
//
|
|
// We aim to insert polls such that running code can quickly be brought to a
|
|
// well defined state for inspection by the collector. In the current
|
|
// implementation, this is done via the insertion of poll sites at method entry
|
|
// and the backedge of most loops. We try to avoid inserting more polls than
|
|
// are necessary to ensure a finite period between poll sites. This is not
|
|
// because the poll itself is expensive in the generated code; it's not. Polls
|
|
// do tend to impact the optimizer itself in negative ways; we'd like to avoid
|
|
// perturbing the optimization of the method as much as we can.
|
|
//
|
|
// We also need to make most call sites parseable. The callee might execute a
|
|
// poll (or otherwise be inspected by the GC). If so, the entire stack
|
|
// (including the suspended frame of the current method) must be parseable.
|
|
//
|
|
// This pass will insert:
|
|
// - Call parse points ("call safepoints") for any call which may need to
|
|
// reach a safepoint during the execution of the callee function.
|
|
// - Backedge safepoint polls and entry safepoint polls to ensure that
|
|
// executing code reaches a safepoint poll in a finite amount of time.
|
|
//
|
|
// We do not currently support return statepoints, but adding them would not
|
|
// be hard. They are not required for correctness - entry safepoints are an
|
|
// alternative - but some GCs may prefer them. Patches welcome.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#ifndef LLVM_TRANSFORMS_SCALAR_PLACESAFEPOINTS_H
|
|
#define LLVM_TRANSFORMS_SCALAR_PLACESAFEPOINTS_H
|
|
|
|
#include "llvm/IR/PassManager.h"
|
|
|
|
namespace llvm {
|
|
|
|
class TargetLibraryInfo;
|
|
|
|
class PlaceSafepointsPass : public PassInfoMixin<PlaceSafepointsPass> {
|
|
public:
|
|
PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
|
|
|
|
bool runImpl(Function &F, const TargetLibraryInfo &TLI);
|
|
|
|
void cleanup() {}
|
|
|
|
private:
|
|
};
|
|
} // namespace llvm
|
|
|
|
#endif // LLVM_TRANSFORMS_SCALAR_PLACESAFEPOINTS_H
|