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This pass is only used for functions with performance annotations (@_noLocks, @_noAllocation). It runs in the mandatory pipeline and specializes all function calls in performance-annotated functions and functions which are called from such functions. In addition, the pass also does some other related optimizations: devirtualization, constant-folding Builtin.canBeClass, inlining of transparent functions and memory access optimizations.
291 lines
10 KiB
C++
291 lines
10 KiB
C++
//===--- GenericSpecializer.cpp - Specialization of generic functions -----===//
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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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// Specialize calls to generic functions by substituting static type
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// information.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "sil-generic-specializer"
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#include "swift/SIL/OptimizationRemark.h"
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#include "swift/SIL/SILFunction.h"
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#include "swift/SIL/SILInstruction.h"
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#include "swift/SILOptimizer/PassManager/Transforms.h"
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#include "swift/SILOptimizer/Utils/BasicBlockOptUtils.h"
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#include "swift/SILOptimizer/Utils/ConstantFolding.h"
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#include "swift/SILOptimizer/Utils/Devirtualize.h"
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#include "swift/SILOptimizer/Utils/Generics.h"
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#include "swift/SILOptimizer/Utils/InstOptUtils.h"
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#include "swift/SILOptimizer/Utils/SILOptFunctionBuilder.h"
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#include "swift/SILOptimizer/Utils/SILInliner.h"
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#include "llvm/ADT/SmallVector.h"
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using namespace swift;
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namespace {
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static bool specializeAppliesInFunction(SILFunction &F,
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SILTransform *transform,
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bool isMandatory) {
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SILOptFunctionBuilder FunctionBuilder(*transform);
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DeadInstructionSet DeadApplies;
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llvm::SmallSetVector<SILInstruction *, 8> Applies;
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OptRemark::Emitter ORE(DEBUG_TYPE, F);
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bool Changed = false;
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for (auto &BB : F) {
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// Collect the applies for this block in reverse order so that we
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// can pop them off the end of our vector and process them in
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// forward order.
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for (auto &I : llvm::reverse(BB)) {
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// Skip non-apply instructions, apply instructions with no
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// substitutions, apply instructions where we do not statically
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// know the called function, and apply instructions where we do
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// not have the body of the called function.
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ApplySite Apply = ApplySite::isa(&I);
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if (!Apply || !Apply.hasSubstitutions())
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continue;
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auto *Callee = Apply.getReferencedFunctionOrNull();
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if (!Callee)
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continue;
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if (!Callee->isDefinition() && !Callee->hasPrespecialization()) {
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ORE.emit([&]() {
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using namespace OptRemark;
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return RemarkMissed("NoDef", I)
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<< "Unable to specialize generic function "
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<< NV("Callee", Callee) << " since definition is not visible";
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});
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continue;
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}
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Applies.insert(Apply.getInstruction());
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}
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// Attempt to specialize each apply we collected, deleting any
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// that we do specialize (along with other instructions we clone
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// in the process of doing so). We pop from the end of the list to
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// avoid tricky iterator invalidation issues.
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while (!Applies.empty()) {
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auto *I = Applies.pop_back_val();
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auto Apply = ApplySite::isa(I);
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assert(Apply && "Expected an apply!");
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SILFunction *Callee = Apply.getReferencedFunctionOrNull();
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assert(Callee && "Expected to have a known callee");
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if (!Apply.canOptimize())
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continue;
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if (!isMandatory && !Callee->shouldOptimize())
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continue;
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// We have a call that can potentially be specialized, so
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// attempt to do so.
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llvm::SmallVector<SILFunction *, 2> NewFunctions;
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trySpecializeApplyOfGeneric(FunctionBuilder, Apply, DeadApplies,
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NewFunctions, ORE, isMandatory);
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// Remove all the now-dead applies. We must do this immediately
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// rather than defer it in order to avoid problems with cloning
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// dead instructions when doing recursive specialization.
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while (!DeadApplies.empty()) {
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auto *AI = DeadApplies.pop_back_val();
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// Remove any applies we are deleting so that we don't attempt
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// to specialize them.
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Applies.remove(AI);
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recursivelyDeleteTriviallyDeadInstructions(AI, true);
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Changed = true;
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}
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if (auto *sft = dyn_cast<SILFunctionTransform>(transform)) {
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// If calling the specialization utility resulted in new functions
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// (as opposed to returning a previous specialization), we need to notify
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// the pass manager so that the new functions get optimized.
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for (SILFunction *NewF : reverse(NewFunctions)) {
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sft->addFunctionToPassManagerWorklist(NewF, Callee);
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}
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}
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}
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}
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return Changed;
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}
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/// The generic specializer, used in the optimization pipeline.
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class GenericSpecializer : public SILFunctionTransform {
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/// The entry point to the transformation.
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void run() override {
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SILFunction &F = *getFunction();
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LLVM_DEBUG(llvm::dbgs() << "***** GenericSpecializer on function:"
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<< F.getName() << " *****\n");
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if (specializeAppliesInFunction(F, this, /*isMandatory*/ false)) {
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invalidateAnalysis(SILAnalysis::InvalidationKind::Everything);
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}
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}
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};
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/// The mandatory specializer, which runs in the mandatory pipeline.
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///
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/// It specializes functions, called from performance-annotated functions
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/// (@_noLocks, @_noAllocation).
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class MandatoryGenericSpecializer : public SILModuleTransform {
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void run() override;
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bool optimize(SILFunction *func, ClassHierarchyAnalysis *cha);
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bool optimizeInst(SILInstruction *inst, SILOptFunctionBuilder &funcBuilder,
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InstructionDeleter &deleter, ClassHierarchyAnalysis *cha);
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};
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void MandatoryGenericSpecializer::run() {
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SILModule *module = getModule();
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if (!module->getOptions().EnablePerformanceAnnotations)
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return;
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ClassHierarchyAnalysis *cha = getAnalysis<ClassHierarchyAnalysis>();
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llvm::SmallVector<SILFunction *, 8> workList;
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llvm::SmallPtrSet<SILFunction *, 16> visited;
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// Look for performance-annotated functions.
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for (SILFunction &function : *module) {
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if (function.getPerfConstraints() != PerformanceConstraints::None) {
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workList.push_back(&function);
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visited.insert(&function);
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}
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}
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while (!workList.empty()) {
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SILFunction *func = workList.pop_back_val();
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module->linkFunction(func, SILModule::LinkingMode::LinkAll);
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if (!func->isDefinition())
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continue;
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// Perform generic specialization and other related optimzations.
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bool changed = optimize(func, cha);
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if (changed)
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invalidateAnalysis(func, SILAnalysis::InvalidationKind::Everything);
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// Continue specializing called functions.
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for (SILBasicBlock &block : *func) {
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for (SILInstruction &inst : block) {
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if (auto as = ApplySite::isa(&inst)) {
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if (SILFunction *callee = as.getReferencedFunctionOrNull()) {
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if (visited.insert(callee).second)
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workList.push_back(callee);
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}
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}
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}
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}
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}
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}
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/// Specialize generic calls in \p func and do some other related optimizations:
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/// devirtualization and constant-folding of the Builtin.canBeClass.
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bool MandatoryGenericSpecializer::optimize(SILFunction *func,
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ClassHierarchyAnalysis *cha) {
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bool changed = false;
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SILOptFunctionBuilder funcBuilder(*this);
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InstructionDeleter deleter;
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ReachingReturnBlocks rrBlocks(func);
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NonErrorHandlingBlocks neBlocks(func);
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// If this is a just specialized function, try to optimize copy_addr, etc.
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// instructions.
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if (optimizeMemoryAccesses(*func)) {
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eliminateDeadAllocations(*func);
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changed = true;
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}
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// Visiting blocks in reverse order avoids revisiting instructions after block
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// splitting, which would be quadratic.
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for (SILBasicBlock &block : llvm::reverse(*func)) {
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// Only consider blocks which are not on a "throw" path.
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if (!rrBlocks.reachesReturn(&block) || !neBlocks.isNonErrorHandling(&block))
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continue;
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for (SILInstruction *inst : deleter.updatingReverseRange(&block)) {
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changed |= optimizeInst(inst, funcBuilder, deleter, cha);
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}
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}
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deleter.cleanupDeadInstructions();
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if (specializeAppliesInFunction(*func, this, /*isMandatory*/ true))
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changed = true;
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return changed;
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}
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bool MandatoryGenericSpecializer::
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optimizeInst(SILInstruction *inst, SILOptFunctionBuilder &funcBuilder,
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InstructionDeleter &deleter, ClassHierarchyAnalysis *cha) {
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if (auto as = ApplySite::isa(inst)) {
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// Specialization opens opportunities to devirtualize method calls.
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ApplySite newAS = tryDevirtualizeApply(as, cha).first;
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if (!newAS)
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return false;
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deleter.forceDelete(as.getInstruction());
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auto newFAS = FullApplySite::isa(newAS.getInstruction());
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if (!newFAS)
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return true;
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SILFunction *callee = newFAS.getReferencedFunctionOrNull();
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if (!callee || callee->isTransparent() == IsNotTransparent)
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return true;
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// If the de-virtualized callee is a transparent function, inline it.
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SILInliner::inlineFullApply(newFAS, SILInliner::InlineKind::MandatoryInline,
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funcBuilder, deleter);
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return true;
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}
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if (auto *bi = dyn_cast<BuiltinInst>(inst)) {
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// Constant-fold the Builtin.canBeClass. This is essential for Array code.
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if (bi->getBuiltinInfo().ID != BuiltinValueKind::CanBeObjCClass)
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return false;
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SILBuilderWithScope builder(bi);
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IntegerLiteralInst *lit = optimizeBuiltinCanBeObjCClass(bi, builder);
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if (!lit)
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return false;
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bi->replaceAllUsesWith(lit);
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ConstantFolder constFolder(funcBuilder, getOptions().AssertConfig,
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/*EnableDiagnostics*/ false);
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constFolder.addToWorklist(lit);
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constFolder.processWorkList();
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deleter.forceDelete(bi);
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return true;
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}
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return false;
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}
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} // end anonymous namespace
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SILTransform *swift::createGenericSpecializer() {
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return new GenericSpecializer();
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}
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SILTransform *swift::createMandatoryGenericSpecializer() {
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return new MandatoryGenericSpecializer();
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}
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