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//===--- SILGenCleanup.cpp ------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2019 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
//
//===----------------------------------------------------------------------===//
///
/// Perform peephole-style "cleanup" to aid SIL diagnostic passes.
///
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "silgen-cleanup"
#include "swift/Basic/Defer.h"
#include "swift/SIL/BasicBlockUtils.h"
#include "swift/SIL/OSSALifetimeCompletion.h"
#include "swift/SIL/PrettyStackTrace.h"
#include "swift/SIL/PrunedLiveness.h"
#include "swift/SIL/SILInstruction.h"
#include "swift/SILOptimizer/Analysis/PostOrderAnalysis.h"
#include "swift/SILOptimizer/PassManager/Transforms.h"
#include "swift/SILOptimizer/Utils/CanonicalizeInstruction.h"
#include "swift/SILOptimizer/Utils/InstOptUtils.h"
using namespace swift;
// Define a CanonicalizeInstruction subclass for use in SILGenCleanup.
struct SILGenCanonicalize final : CanonicalizeInstruction {
bool changed = false;
llvm::SmallPtrSet<SILInstruction *, 16> deadOperands;
SILGenCanonicalize(DeadEndBlocks &deadEndBlocks)
: CanonicalizeInstruction(DEBUG_TYPE, deadEndBlocks) {}
void notifyNewInstruction(SILInstruction *) override { changed = true; }
// Just delete the given 'inst' and record its operands. The callback isn't
// allowed to mutate any other instructions.
void killInstruction(SILInstruction *inst) override {
deadOperands.erase(inst);
for (auto &operand : inst->getAllOperands()) {
if (auto *operInst = operand.get()->getDefiningInstruction())
deadOperands.insert(operInst);
}
inst->eraseFromParent();
changed = true;
}
void notifyHasNewUsers(SILValue) override { changed = true; }
/// Delete trivially dead instructions in non-deterministic order.
///
/// We either have that nextII is endII or if nextII is not endII then endII
/// is nextII->getParent()->end().
SILBasicBlock::iterator deleteDeadOperands(SILBasicBlock::iterator nextII,
SILBasicBlock::iterator endII) {
auto callbacks = InstModCallbacks().onDelete([&](SILInstruction *deadInst) {
LLVM_DEBUG(llvm::dbgs() << "Trivially dead: " << *deadInst);
// If nextII is the instruction we are going to delete, move nextII past
// it.
if (deadInst->getIterator() == nextII)
++nextII;
// Then remove the instruction from the set and delete it.
deadOperands.erase(deadInst);
deadInst->eraseFromParent();
});
while (!deadOperands.empty()) {
SILInstruction *deadOperInst = *deadOperands.begin();
// Make sure at least the first instruction is removed from the set.
deadOperands.erase(deadOperInst);
// Then delete this instruction/everything else that we can.
eliminateDeadInstruction(deadOperInst, callbacks);
}
return nextII;
}
};
//===----------------------------------------------------------------------===//
// SILGenCleanup: Top-Level Module Transform
//===----------------------------------------------------------------------===//
namespace {
// SILGenCleanup must run on all functions that will be seen by any analysis
// used by diagnostics before transforming the function that requires the
// analysis. e.g. Closures need to be cleaned up before the closure's parent can
// be diagnosed.
//
// TODO: This pass can be converted to a function transform if the mandatory
// pipeline runs in bottom-up closure order.
struct SILGenCleanup : SILModuleTransform {
void run() override;
bool completeOSSALifetimes(SILFunction *function);
};
bool SILGenCleanup::completeOSSALifetimes(SILFunction *function) {
if (!getModule()->getOptions().OSSACompleteLifetimes)
return false;
bool changed = false;
// Lifetimes must be completed inside out (bottom-up in the CFG).
PostOrderFunctionInfo *postOrder =
getAnalysis<PostOrderAnalysis>()->get(function);
OSSALifetimeCompletion completion(function, /*DomInfo*/nullptr);
for (auto *block : postOrder->getPostOrder()) {
for (SILInstruction &inst : reverse(*block)) {
for (auto result : inst.getResults()) {
if (completion.completeOSSALifetime(result) ==
LifetimeCompletion::WasCompleted) {
changed = true;
}
}
}
for (SILArgument *arg : block->getArguments()) {
assert(!arg->isReborrow() && "reborrows not legal at this SIL stage");
if (completion.completeOSSALifetime(arg) ==
LifetimeCompletion::WasCompleted) {
changed = true;
}
}
}
function->verifyOwnership(/*deadEndBlocks=*/nullptr);
return changed;
}
void SILGenCleanup::run() {
auto &module = *getModule();
for (auto &function : module) {
if (!function.isDefinition())
continue;
PrettyStackTraceSILFunction stackTrace("silgen cleanup", &function);
LLVM_DEBUG(llvm::dbgs()
<< "\nRunning SILGenCleanup on " << function.getName() << "\n");
bool changed = completeOSSALifetimes(&function);
DeadEndBlocks deadEndBlocks(&function);
SILGenCanonicalize sgCanonicalize(deadEndBlocks);
// Iterate over all blocks even if they aren't reachable. No phi-less
// dataflow cycles should have been created yet, and these transformations
// are simple enough they shouldn't be affected by cycles.
for (auto &bb : function) {
for (auto ii = bb.begin(), ie = bb.end(); ii != ie;) {
ii = sgCanonicalize.canonicalize(&*ii);
ii = sgCanonicalize.deleteDeadOperands(ii, ie);
}
}
changed |= sgCanonicalize.changed;
if (changed) {
auto invalidKind = SILAnalysis::InvalidationKind::Instructions;
invalidateAnalysis(&function, invalidKind);
}
}
}
} // end anonymous namespace
SILTransform *swift::createSILGenCleanup() { return new SILGenCleanup(); }
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