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359 lines
12 KiB
C++
359 lines
12 KiB
C++
//===- PerformanceInliner.cpp - Basic cost based inlining for performance -===//
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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 - 2015 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 http://swift.org/LICENSE.txt for license information
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// See http://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 "sil-inliner"
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#include "swift/SIL/SILInstruction.h"
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#include "swift/SIL/CallGraph.h"
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#include "swift/SIL/SILModule.h"
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#include "swift/SILPasses/Passes.h"
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#include "swift/SILPasses/Utils/SILInliner.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/ADT/MapVector.h"
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using namespace swift;
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static llvm::cl::opt<unsigned>
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InlineCostThreshold("sil-inline-threshold", llvm::cl::Hidden,
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llvm::cl::init(50));
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STATISTIC(NumFunctionsInlined, "Number of functions inlined");
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//===----------------------------------------------------------------------===//
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// Call Graph Creation
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//===----------------------------------------------------------------------===//
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/// \brief Returns a SILFunction if this ApplyInst calls a recognizable function
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/// that is legal to inline.
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static SILFunction *getInlinableFunction(ApplyInst *AI) {
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// Avoid substituion lists, we don't support them.
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if (AI->hasSubstitutions())
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return nullptr;
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auto *FRI = dyn_cast<FunctionRefInst>(AI->getCallee().getDef());
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if (!FRI)
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return nullptr;
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SILFunction *F = FRI->getReferencedFunction();
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if (F->empty() || F->isExternalDeclaration()) {
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DEBUG(llvm::dbgs() << " Can't inline " << F->getName() << ".\n");
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return nullptr;
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}
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DEBUG(llvm::dbgs() << " Can inline " << F->getName() << ".\n");
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return F;
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}
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/// Return the bottom up call-graph order for module M. Notice that we don't
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/// include functions that don't participate in any call (caller or callee).
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static void TopDownCallGraphOrder(SILModule *M,
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std::vector<SILFunction *> &order) {
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CallGraphSorter<SILFunction *> sorter;
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// Construct the call graph, mapping callee to callers to that the resulting
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// topological ordering has callees before callers.
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//
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// *NOTE* From the typical callgraph perspective, we are inserting edges in
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// reverse.
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for (auto &Caller : *M)
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for (auto &BB : Caller)
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for (auto &I : BB)
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if (FunctionRefInst *FRI = dyn_cast<FunctionRefInst>(&I)) {
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SILFunction *Callee = FRI->getReferencedFunction();
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sorter.addEdge(Callee, &Caller);
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}
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// Perform the topological sorting.
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sorter.sort(order);
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}
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//===----------------------------------------------------------------------===//
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// Cost Model
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//===----------------------------------------------------------------------===//
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namespace {
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// For now Free is 0 and Expensive is 1. This can be changed in the future by
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// adding more categories.
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enum class InlineCost {
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Free = 0,
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Expensive = 1,
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};
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} // end anonymous namespace
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/// For now just assume that every SIL instruction is one to one with an LLVM
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/// instruction. This is of course very much so not true.
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///
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/// TODO: Fill this out.
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static InlineCost instructionInlineCost(SILInstruction &I) {
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switch (I.getKind()) {
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case ValueKind::FunctionRefInst:
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case ValueKind::BuiltinFunctionRefInst:
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case ValueKind::GlobalAddrInst:
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case ValueKind::SILGlobalAddrInst:
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case ValueKind::IntegerLiteralInst:
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case ValueKind::FloatLiteralInst:
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case ValueKind::DebugValueInst:
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case ValueKind::DebugValueAddrInst:
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return InlineCost::Free;
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case ValueKind::TupleElementAddrInst:
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case ValueKind::StructElementAddrInst: {
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// A gep whose operand is a gep with no other users will get folded by
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// LLVM into one gep implying the second should be free.
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SILValue Op = I.getOperand(0);
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if ((Op->getKind() == ValueKind::TupleElementAddrInst ||
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Op->getKind() == ValueKind::StructElementAddrInst) &&
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Op->hasOneUse())
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return InlineCost::Free;
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}
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// Aggregates are exploded at the IR level; these are effectively no-ops.
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case ValueKind::TupleInst:
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case ValueKind::StructInst:
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case ValueKind::StructExtractInst:
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case ValueKind::TupleExtractInst:
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return InlineCost::Free;
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// Unchecked casts are free.
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case ValueKind::AddressToPointerInst:
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case ValueKind::PointerToAddressInst:
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case ValueKind::ObjectPointerToRefInst:
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case ValueKind::RefToObjectPointerInst:
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case ValueKind::RawPointerToRefInst:
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case ValueKind::RefToRawPointerInst:
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case ValueKind::UpcastExistentialRefInst:
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case ValueKind::UpcastInst:
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case ValueKind::ThinToThickFunctionInst:
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case ValueKind::ConvertFunctionInst:
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return InlineCost::Free;
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// Arguments and undef are free.
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case ValueKind::SILArgument:
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case ValueKind::SILUndef:
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llvm_unreachable("Only instructions should be passed into this "
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"function.");
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case ValueKind::MetatypeInst:
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// Thin metatypes are always free.
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if (I.getType(0).castTo<MetatypeType>()->isThin())
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return InlineCost::Free;
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// TODO: Thick metatypes are free if they don't require generic or lazy
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// instantiation.
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return InlineCost::Expensive;
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// Return and unreachable are free.
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case ValueKind::UnreachableInst:
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case ValueKind::ReturnInst:
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return InlineCost::Free;
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// TODO
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case ValueKind::AllocArrayInst:
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case ValueKind::AllocBoxInst:
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case ValueKind::AllocRefInst:
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case ValueKind::AllocStackInst:
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case ValueKind::ApplyInst:
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case ValueKind::ArchetypeMetatypeInst:
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case ValueKind::ArchetypeMethodInst:
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case ValueKind::ArchetypeRefToSuperInst:
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case ValueKind::AssignInst:
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case ValueKind::AutoreleaseReturnInst:
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case ValueKind::BranchInst:
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case ValueKind::BridgeToBlockInst:
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case ValueKind::CheckedCastBranchInst:
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case ValueKind::ClassMetatypeInst:
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case ValueKind::ClassMethodInst:
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case ValueKind::CondBranchInst:
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case ValueKind::CondFailInst:
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case ValueKind::CopyAddrInst:
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case ValueKind::CopyValueInst:
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case ValueKind::DeallocBoxInst:
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case ValueKind::DeallocRefInst:
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case ValueKind::DeallocStackInst:
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case ValueKind::DeinitExistentialInst:
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case ValueKind::DestroyAddrInst:
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case ValueKind::DestroyValueInst:
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case ValueKind::DynamicMethodBranchInst:
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case ValueKind::DynamicMethodInst:
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case ValueKind::EnumInst:
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case ValueKind::IndexAddrInst:
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case ValueKind::IndexRawPointerInst:
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case ValueKind::InitEnumDataAddrInst:
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case ValueKind::InitExistentialInst:
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case ValueKind::InitExistentialRefInst:
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case ValueKind::InjectEnumAddrInst:
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case ValueKind::IsNonnullInst:
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case ValueKind::LoadInst:
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case ValueKind::LoadWeakInst:
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case ValueKind::PartialApplyInst:
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case ValueKind::PeerMethodInst:
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case ValueKind::ProjectExistentialInst:
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case ValueKind::ProjectExistentialRefInst:
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case ValueKind::ProtocolMetatypeInst:
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case ValueKind::ProtocolMethodInst:
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case ValueKind::RefElementAddrInst:
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case ValueKind::RefToUnownedInst:
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case ValueKind::StoreInst:
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case ValueKind::StoreWeakInst:
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case ValueKind::StringLiteralInst:
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case ValueKind::StrongReleaseInst:
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case ValueKind::StrongRetainAutoreleasedInst:
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case ValueKind::StrongRetainInst:
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case ValueKind::StrongRetainUnownedInst:
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case ValueKind::SuperMethodInst:
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case ValueKind::SwitchEnumAddrInst:
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case ValueKind::SwitchEnumInst:
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case ValueKind::SwitchIntInst:
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case ValueKind::TakeEnumDataAddrInst:
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case ValueKind::UnconditionalCheckedCastInst:
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case ValueKind::UnownedReleaseInst:
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case ValueKind::UnownedRetainInst:
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case ValueKind::UnownedToRefInst:
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case ValueKind::UpcastExistentialInst:
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return InlineCost::Expensive;
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case ValueKind::MarkFunctionEscapeInst:
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case ValueKind::MarkUninitializedInst:
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llvm_unreachable("not valid in canonical sil");
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}
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}
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/// \brief Returns the inlining cost of the function.
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static unsigned getFunctionCost(SILFunction *F) {
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DEBUG(llvm::dbgs() << " Calculating cost for " << F->getName() << ".\n");
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if (F->isTransparent() == IsTransparent_t::IsTransparent)
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return 0;
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unsigned Cost = 0;
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for (auto &BB : *F) {
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for (auto &I : BB) {
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Cost += unsigned(instructionInlineCost(I));
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// If we're debugging, continue calculating the total cost even if we
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// passed the threshold.
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DEBUG(goto next);
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// If i is greater than the InlineCostThreshold, we already know we are
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// not going to inline this given function, so there is no point in
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// continuing to visit instructions.
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if (Cost > InlineCostThreshold) {
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return Cost;
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}
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goto next;
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next:;
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}
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}
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DEBUG(llvm::dbgs() << " Found cost: " << Cost << "\n");
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return Cost;
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}
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//===----------------------------------------------------------------------===//
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// Inliner
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//===----------------------------------------------------------------------===//
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/// Attempt to inline all calls smaller than our threshold into F until.
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static void inlineCallsIntoFunction(SILFunction *Caller) {
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SILInliner Inliner(*Caller, SILInliner::InlineKind::PerformanceInline);
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DEBUG(llvm::dbgs() << "Visiting Function: " << Caller->getName() << "\n");
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llvm::SmallVector<ApplyInst*, 8> CallSites;
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// Collect all of the ApplyInsts in this function. We will be changing the
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// control flow and collecting the AIs simplifies the scan.
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for (auto &BB : *Caller) {
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auto I = BB.begin(), E = BB.end();
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while (I != E) {
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// Check if this is a call site.
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ApplyInst *AI = dyn_cast<ApplyInst>(I++);
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if (AI)
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CallSites.push_back(AI);
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}
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}
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for (auto AI : CallSites) {
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DEBUG(llvm::dbgs() << " Found call site:" << *AI);
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// Get the callee.
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SILFunction *Callee = getInlinableFunction(AI);
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if (!Callee)
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continue;
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DEBUG(llvm::dbgs() << " Found callee:" << Callee->getName() << ".\n");
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// Prevent circular inlining.
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if (Callee == Caller) {
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DEBUG(llvm::dbgs() << " Skipping recursive calls.\n");
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continue;
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}
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// Calculate the inlining cost of the callee.
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unsigned CalleeCost = getFunctionCost(Callee);
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if (CalleeCost > InlineCostThreshold) {
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DEBUG(llvm::dbgs() << " Function too big to inline. Skipping.\n");
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continue;
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}
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// Add the arguments from AI into a SILValue list.
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SmallVector<SILValue, 8> Args;
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for (const auto &Arg : AI->getArguments())
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Args.push_back(Arg);
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// Ok, we are within budget. Attempt to inline.
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DEBUG(llvm::dbgs() << " Inlining " << Callee->getName() << " Into " <<
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Caller->getName() << "\n");
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// We already moved the iterator to the next instruction because the AI
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// will be erased by the inliner. Notice that we will skip all of the
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// newly inlined ApplyInsts. That's okay because we will visit them in
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// our next invocation of the inliner.
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Inliner.inlineFunction(AI, Callee, ArrayRef<Substitution>(), Args);
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NumFunctionsInlined++;
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}
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}
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//===----------------------------------------------------------------------===//
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// Top Level Driver
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//===----------------------------------------------------------------------===//
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void swift::performSILPerformanceInlining(SILModule *M) {
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DEBUG(llvm::dbgs() << "*** SIL Performance Inlining ***\n\n");
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if (InlineCostThreshold == 0) {
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DEBUG(llvm::dbgs() << "*** The SIL performance Inliner is disabled ***\n");
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return;
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}
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// Collect a call-graph bottom-up list of functions.
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std::vector<SILFunction *> Worklist;
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TopDownCallGraphOrder(M, Worklist);
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// For each function in the worklist, attempt to inline its list of apply
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// inst.
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while (Worklist.size()) {
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SILFunction *F = Worklist.back();
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Worklist.pop_back();
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// Do not inline into transparent functions. This is exposing a diagnostics
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// bug. We will still inline after we perform mandatory inlining of the
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// transparent function.
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inlineCallsIntoFunction(F);
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}
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}
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