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//=----------- Reachability.cpp - Walking from roots to barriers. -----------=//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
#include "swift/SILOptimizer/Analysis/Reachability.h"
using namespace swift;
/// Walks backwards from the specified roots to find barrier instructions, phis,
/// and blocks via the isBarrier predicate.
///
/// Implements IterativeBackwardReachability::Effects
/// Implements IterativeBackwardReachability::findBarriers::Visitor
class FindBarriersBackwardDataflow final {
using Reachability =
IterativeBackwardReachability<FindBarriersBackwardDataflow>;
using Effect = Reachability::Effect;
ArrayRef<SILInstruction *> const roots;
function_ref<bool(SILInstruction *)> isBarrier;
ReachableBarriers &barriers;
Reachability::Result result;
Reachability reachability;
public:
FindBarriersBackwardDataflow(SILFunction &function,
ArrayRef<SILInstruction *> roots,
ArrayRef<SILBasicBlock *> stopBlocks,
ReachableBarriers &barriers,
function_ref<bool(SILInstruction *)> isBarrier)
: roots(roots), isBarrier(isBarrier), barriers(barriers),
result(&function), reachability(&function, stopBlocks, *this, result) {}
FindBarriersBackwardDataflow(FindBarriersBackwardDataflow const &) = delete;
FindBarriersBackwardDataflow &
operator=(FindBarriersBackwardDataflow const &) = delete;
void run();
private:
friend Reachability;
/// IterativeBackwardReachability::Effects
auto gens() { return roots; }
Effect effectForInstruction(SILInstruction *);
Effect effectForPhi(SILBasicBlock *);
auto localGens() { return result.localGens; }
bool isLocalGen(SILInstruction *instruction) {
return result.localGens.contains(instruction);
}
/// IterativeBackwardReachability::findBarriers::Visitor
void visitBarrierInstruction(SILInstruction *instruction) {
barriers.instructions.push_back(instruction);
}
void visitBarrierPhi(SILBasicBlock *block) { barriers.phis.push_back(block); }
void visitBarrierBlock(SILBasicBlock *block) {
barriers.edges.push_back(block);
}
void visitInitialBlock(SILBasicBlock *block) {
barriers.initialBlocks.push_back(block);
}
};
FindBarriersBackwardDataflow::Effect
FindBarriersBackwardDataflow::effectForInstruction(
SILInstruction *instruction) {
if (llvm::is_contained(roots, instruction))
return Effect::Gen();
auto barrier = isBarrier(instruction);
return barrier ? Effect::Kill() : Effect::NoEffect();
}
FindBarriersBackwardDataflow::Effect
FindBarriersBackwardDataflow::effectForPhi(SILBasicBlock *block) {
assert(llvm::all_of(block->getArguments(),
[&](auto argument) { return PhiValue(argument); }));
bool barrier =
llvm::any_of(block->getPredecessorBlocks(), [&](auto *predecessor) {
return isBarrier(predecessor->getTerminator());
});
return barrier ? Effect::Kill() : Effect::NoEffect();
}
void FindBarriersBackwardDataflow::run() {
reachability.initialize();
reachability.solve();
reachability.findBarriers(*this);
}
void swift::findBarriersBackward(
ArrayRef<SILInstruction *> roots, ArrayRef<SILBasicBlock *> initialBlocks,
SILFunction &function, ReachableBarriers &barriers,
function_ref<bool(SILInstruction *)> isBarrier) {
FindBarriersBackwardDataflow flow(function, roots, initialBlocks, barriers,
isBarrier);
flow.run();
}
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