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//===--- DeadArgumentTransform.cpp ----------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 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
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "fso-dead-argument-transform"
#include "FunctionSignatureOpts.h"
#include "swift/SIL/DebugUtils.h"
#include "llvm/Support/CommandLine.h"
using namespace swift;
static llvm::cl::opt<bool> FSODisableDeadArgument(
"sil-fso-disable-dead-argument",
llvm::cl::desc("Do not perform dead argument elimination during FSO. "
"Intended only for testing purposes"));
bool FunctionSignatureTransform::DeadArgumentAnalyzeParameters() {
if (FSODisableDeadArgument)
return false;
// Did we decide we should optimize any parameter?
SILFunction *F = TransformDescriptor.OriginalFunction;
bool SignatureOptimize = false;
auto Args = F->begin()->getSILFunctionArguments();
auto OrigShouldModifySelfArgument =
TransformDescriptor.shouldModifySelfArgument;
// Analyze the argument information.
for (unsigned i : indices(Args)) {
ArgumentDescriptor &A = TransformDescriptor.ArgumentDescList[i];
if (!A.PInfo.has_value()) {
// It is not an argument. It could be an indirect result.
continue;
}
if (!A.canOptimizeLiveArg()) {
continue;
}
// Check whether argument is dead.
if (!hasNonTrivialNonDebugTransitiveUsers(Args[i])) {
A.IsEntirelyDead = true;
SignatureOptimize = true;
if (Args[i]->isSelf())
TransformDescriptor.shouldModifySelfArgument = true;
}
}
if (F->getLoweredFunctionType()->isPolymorphic()) {
// If the set of dead arguments contains only type arguments,
// don't remove them, because it would produce a slower code
// for generic functions.
bool HasNonTypeDeadArguments = false;
for (auto &AD : TransformDescriptor.ArgumentDescList) {
if (AD.IsEntirelyDead &&
!isa<AnyMetatypeType>(AD.Arg->getType().getASTType())) {
HasNonTypeDeadArguments = true;
break;
}
}
if (!HasNonTypeDeadArguments) {
for (auto &AD : TransformDescriptor.ArgumentDescList) {
if (AD.IsEntirelyDead) {
AD.IsEntirelyDead = false;
}
}
TransformDescriptor.shouldModifySelfArgument =
OrigShouldModifySelfArgument;
SignatureOptimize = false;
}
}
return SignatureOptimize;
}
void FunctionSignatureTransform::DeadArgumentTransformFunction() {
SILFunction *F = TransformDescriptor.OriginalFunction;
SILBasicBlock *BB = &*F->begin();
for (const ArgumentDescriptor &AD : TransformDescriptor.ArgumentDescList) {
if (!AD.IsEntirelyDead)
continue;
eraseUsesOfValue(BB->getArgument(AD.Index));
}
}
void FunctionSignatureTransform::DeadArgumentFinalizeOptimizedFunction() {
auto *BB = &*TransformDescriptor.OptimizedFunction.get()->begin();
// Remove any dead argument starting from the last argument to the first.
for (ArgumentDescriptor &AD : reverse(TransformDescriptor.ArgumentDescList)) {
if (!AD.IsEntirelyDead)
continue;
AD.WasErased = true;
BB->eraseArgument(AD.Arg->getIndex());
}
}
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