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114 lines
3.9 KiB
C++
114 lines
3.9 KiB
C++
//===--- DeadArgumentTransform.cpp ----------------------------------------===//
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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 - 2018 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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#define DEBUG_TYPE "fso-dead-argument-transform"
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#include "FunctionSignatureOpts.h"
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#include "swift/SIL/DebugUtils.h"
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#include "llvm/Support/CommandLine.h"
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using namespace swift;
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static llvm::cl::opt<bool> FSODisableDeadArgument(
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"sil-fso-disable-dead-argument",
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llvm::cl::desc("Do not perform dead argument elimination during FSO. "
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"Intended only for testing purposes"));
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bool FunctionSignatureTransform::DeadArgumentAnalyzeParameters() {
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if (FSODisableDeadArgument)
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return false;
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// Did we decide we should optimize any parameter?
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SILFunction *F = TransformDescriptor.OriginalFunction;
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// If a function has lifetime dependencies, disable FSO's dead param
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// optimization. Dead params maybe dependency sources and we should not
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// delete them. It is also problematic to dead code params that are not
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// dependency sources, since lifetime dependent sources are stored as indices
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// and deleting dead parameters will require recomputation of these indices.
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if (F->getLoweredFunctionType()->hasLifetimeDependencies()) {
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return false;
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}
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bool SignatureOptimize = false;
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auto Args = F->begin()->getSILFunctionArguments();
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auto OrigShouldModifySelfArgument =
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TransformDescriptor.shouldModifySelfArgument;
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// Analyze the argument information.
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for (unsigned i : indices(Args)) {
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ArgumentDescriptor &A = TransformDescriptor.ArgumentDescList[i];
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if (!A.PInfo.has_value()) {
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// It is not an argument. It could be an indirect result.
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continue;
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}
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if (!A.canOptimizeLiveArg()) {
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continue;
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}
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// Check whether argument is dead.
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if (!hasNonTrivialNonDebugTransitiveUsers(Args[i])) {
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A.IsEntirelyDead = true;
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SignatureOptimize = true;
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if (Args[i]->isSelf())
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TransformDescriptor.shouldModifySelfArgument = true;
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}
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}
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if (F->getLoweredFunctionType()->isPolymorphic()) {
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// If the set of dead arguments contains only type arguments,
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// don't remove them, because it would produce a slower code
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// for generic functions.
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bool HasNonTypeDeadArguments = false;
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for (auto &AD : TransformDescriptor.ArgumentDescList) {
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if (AD.IsEntirelyDead &&
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!isa<AnyMetatypeType>(AD.Arg->getType().getASTType())) {
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HasNonTypeDeadArguments = true;
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break;
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}
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}
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if (!HasNonTypeDeadArguments) {
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for (auto &AD : TransformDescriptor.ArgumentDescList) {
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if (AD.IsEntirelyDead) {
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AD.IsEntirelyDead = false;
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}
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}
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TransformDescriptor.shouldModifySelfArgument =
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OrigShouldModifySelfArgument;
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SignatureOptimize = false;
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}
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}
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return SignatureOptimize;
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}
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void FunctionSignatureTransform::DeadArgumentTransformFunction() {
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SILFunction *F = TransformDescriptor.OriginalFunction;
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SILBasicBlock *BB = &*F->begin();
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for (const ArgumentDescriptor &AD : TransformDescriptor.ArgumentDescList) {
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if (!AD.IsEntirelyDead)
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continue;
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eraseUsesOfValue(BB->getArgument(AD.Index));
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}
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}
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void FunctionSignatureTransform::DeadArgumentFinalizeOptimizedFunction() {
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auto *BB = &*TransformDescriptor.OptimizedFunction.get()->begin();
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// Remove any dead argument starting from the last argument to the first.
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for (ArgumentDescriptor &AD : reverse(TransformDescriptor.ArgumentDescList)) {
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if (!AD.IsEntirelyDead)
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continue;
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AD.WasErased = true;
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BB->eraseArgument(AD.Arg->getIndex());
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}
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}
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