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//===--- Devirtualizer.cpp - Devirtualize indirect calls -----------------===//
// This source file is part of the open source project
// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
// See for license information
// See for the list of Swift project authors
// Devirtualize indirect calls to functions, turning them into direct function
// references.
#define DEBUG_TYPE "sil-devirtualizer"
#include "swift/SIL/OptimizationRemark.h"
#include "swift/SIL/SILFunction.h"
#include "swift/SIL/SILInstruction.h"
#include "swift/SILOptimizer/Analysis/ClassHierarchyAnalysis.h"
#include "swift/SILOptimizer/Utils/Devirtualize.h"
#include "swift/SILOptimizer/PassManager/Transforms.h"
#include "llvm/ADT/SmallVector.h"
using namespace swift;
namespace {
class Devirtualizer : public SILFunctionTransform {
bool Changed = false;
bool ChangedCFG = false;
void devirtualizeAppliesInFunction(SILFunction &F,
ClassHierarchyAnalysis *CHA);
/// The entry point to the transformation.
void run() override {
SILFunction &F = *getFunction();
ClassHierarchyAnalysis *CHA = PM->getAnalysis<ClassHierarchyAnalysis>();
LLVM_DEBUG(llvm::dbgs() << "***** Devirtualizer on function:" << F.getName()
<< " *****\n");
Changed = false;
ChangedCFG = false;
devirtualizeAppliesInFunction(F, CHA);
if (ChangedCFG)
else if (Changed)
} // end anonymous namespace
// Return true if any calls changed, and true if the CFG also changed.
void Devirtualizer::devirtualizeAppliesInFunction(SILFunction &F,
ClassHierarchyAnalysis *CHA) {
llvm::SmallVector<ApplySite, 8> NewApplies;
OptRemark::Emitter ORE(DEBUG_TYPE, F);
SmallVector<ApplySite, 16> Applies;
for (auto &BB : F) {
for (auto It = BB.begin(), End = BB.end(); It != End;) {
auto &I = *It++;
// Skip non-apply instructions.
auto Apply = ApplySite::isa(&I);
if (!Apply)
for (auto Apply : Applies) {
ApplySite NewInst;
bool modifiedCFG;
std::tie(NewInst, modifiedCFG) = tryDevirtualizeApply(Apply, CHA, &ORE);
if (!NewInst)
Changed = true;
ChangedCFG |= modifiedCFG;
// For each new apply, attempt to link in function bodies if we do
// not already have them, then notify the pass manager of the new
// functions.
// We do this after deleting the old applies because otherwise we
// hit verification errors in the linking code due to having
// non-cond_br critical edges.
while (!NewApplies.empty()) {
auto Apply = NewApplies.pop_back_val();
auto *CalleeFn = Apply.getInitiallyReferencedFunction();
assert(CalleeFn && "Expected devirtualized callee!");
// We need to ensure that we link after devirtualizing in order to pull in
// everything we reference from another module, which may expose optimization
// opportunities and is also needed for correctness if we reference functions
// with non-public linkage. See lib/SIL/Linker.cpp for details.
if (!CalleeFn->isDefinition())
F.getModule().linkFunction(CalleeFn, SILModule::LinkingMode::LinkAll);
// We may not have optimized these functions yet, and it could
// be beneficial to rerun some earlier passes on the current
// function now that we've made these direct references visible.
if (CalleeFn->isDefinition() && CalleeFn->shouldOptimize())
addFunctionToPassManagerWorklist(CalleeFn, nullptr);
SILTransform *swift::createDevirtualizer() { return new Devirtualizer(); }