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a92e9b3288
A class which is marked as internal or public can be visible outside of the current file, where the use of the VWT indirectly is possible. If the VWT is modified and inlined, it is possible that the offsets will no longer match resulting in an invalid dispatch. Limit the pass to when WMO is enabled or the type is private in non-WMO cases.
119 lines
4.1 KiB
C++
119 lines
4.1 KiB
C++
//===--- PruneVTables.cpp - Prune unnecessary vtable entries --------------===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See https://swift.org/LICENSE.txt for license information
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// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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//
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// Mark sil_vtable entries as [nonoverridden] when possible, so that we know
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// at IRGen time they can be elided from runtime vtables.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "prune-vtables"
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#include "swift/SILOptimizer/PassManager/Transforms.h"
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#include "swift/SILOptimizer/Utils/InstOptUtils.h"
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STATISTIC(NumNonoverriddenVTableEntries,
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"# of vtable entries marked non-overridden");
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using namespace swift;
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namespace {
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class PruneVTables : public SILModuleTransform {
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void runOnVTable(SILModule *M, SILVTable *vtable) {
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LLVM_DEBUG(llvm::dbgs() << "PruneVTables inspecting table:\n";
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vtable->print(llvm::dbgs()));
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if (!M->isWholeModule() &&
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vtable->getClass()->getEffectiveAccess() >= AccessLevel::FilePrivate) {
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LLVM_DEBUG(llvm::dbgs() << "Ignoring visible table: ";
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vtable->print(llvm::dbgs()));
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return;
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}
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for (auto &entry : vtable->getMutableEntries()) {
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// We don't need to worry about entries that are overridden,
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// or have already been found to have no overrides.
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if (entry.isNonOverridden()) {
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LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
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entry.getMethod().print(llvm::dbgs());
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llvm::dbgs() << " is already nonoverridden\n");
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continue;
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}
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switch (entry.getKind()) {
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case SILVTable::Entry::Normal:
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case SILVTable::Entry::Inherited:
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break;
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case SILVTable::Entry::Override:
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LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
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entry.getMethod().print(llvm::dbgs());
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llvm::dbgs() << " is an override\n");
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continue;
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}
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// The destructor entry must remain.
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if (entry.getMethod().kind == SILDeclRef::Kind::Deallocator) {
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LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
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entry.getMethod().print(llvm::dbgs());
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llvm::dbgs() << " is a destructor\n");
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continue;
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}
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auto methodDecl = entry.getMethod().getAbstractFunctionDecl();
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if (!methodDecl) {
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LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
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entry.getMethod().print(llvm::dbgs());
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llvm::dbgs() << " is not a function decl\n");
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continue;
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}
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// Is the method declared final?
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if (!methodDecl->isFinal()) {
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// Are callees of this entry statically knowable?
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if (!calleesAreStaticallyKnowable(*M, entry.getMethod())) {
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LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
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entry.getMethod().print(llvm::dbgs());
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llvm::dbgs() << " does not have statically-knowable callees\n");
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continue;
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}
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// Does the method have any overrides in this module?
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if (methodDecl->isOverridden()) {
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LLVM_DEBUG(llvm::dbgs() << "-- entry for ";
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entry.getMethod().print(llvm::dbgs());
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llvm::dbgs() << " has overrides\n");
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continue;
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}
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}
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LLVM_DEBUG(llvm::dbgs() << "++ entry for ";
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entry.getMethod().print(llvm::dbgs());
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llvm::dbgs() << " can be marked non-overridden!\n");
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++NumNonoverriddenVTableEntries;
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entry.setNonOverridden(true);
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vtable->updateVTableCache(entry);
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}
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}
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void run() override {
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SILModule *M = getModule();
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for (auto &vtable : M->getVTables()) {
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runOnVTable(M, vtable);
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}
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}
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};
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}
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SILTransform *swift::createPruneVTables() {
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return new PruneVTables();
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}
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