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//===---------- speculation.cpp - Utilities for Speculation ----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/ExecutionEngine/Orc/Speculation.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/IR/Verifier.h"
#include "llvm/Support/Debug.h"
#include <vector>
namespace llvm {
namespace orc {
// ImplSymbolMap methods
void ImplSymbolMap::trackImpls(SymbolAliasMap ImplMaps, JITDylib *SrcJD) {
assert(SrcJD && "Tracking on Null Source .impl dylib");
std::lock_guard<std::mutex> Lockit(ConcurrentAccess);
for (auto &I : ImplMaps) {
auto It = Maps.insert({I.first, {I.second.Aliasee, SrcJD}});
// check rationale when independent dylibs have same symbol name?
assert(It.second && "ImplSymbols are already tracked for this Symbol?");
(void)(It);
}
}
// Trigger Speculative Compiles.
void Speculator::speculateForEntryPoint(Speculator *Ptr, uint64_t StubId) {
assert(Ptr && " Null Address Received in orc_speculate_for ");
Ptr->speculateFor(StubId);
}
Error Speculator::addSpeculationRuntime(JITDylib &JD,
MangleAndInterner &Mangle) {
JITEvaluatedSymbol ThisPtr(pointerToJITTargetAddress(this),
JITSymbolFlags::Exported);
JITEvaluatedSymbol SpeculateForEntryPtr(
pointerToJITTargetAddress(&speculateForEntryPoint),
JITSymbolFlags::Exported);
return JD.define(absoluteSymbols({
{Mangle("__orc_speculator"), ThisPtr}, // Data Symbol
{Mangle("__orc_speculate_for"), SpeculateForEntryPtr} // Callable Symbol
}));
}
// If two modules, share the same LLVMContext, different threads must
// not access them concurrently without locking the associated LLVMContext
// this implementation follows this contract.
void IRSpeculationLayer::emit(MaterializationResponsibility R,
ThreadSafeModule TSM) {
assert(TSM && "Speculation Layer received Null Module ?");
assert(TSM.getContext().getContext() != nullptr &&
"Module with null LLVMContext?");
// Instrumentation of runtime calls, lock the Module
TSM.withModuleDo([this, &R](Module &M) {
auto &MContext = M.getContext();
auto SpeculatorVTy = StructType::create(MContext, "Class.Speculator");
auto RuntimeCallTy = FunctionType::get(
Type::getVoidTy(MContext),
{SpeculatorVTy->getPointerTo(), Type::getInt64Ty(MContext)}, false);
auto RuntimeCall =
Function::Create(RuntimeCallTy, Function::LinkageTypes::ExternalLinkage,
"__orc_speculate_for", &M);
auto SpeclAddr = new GlobalVariable(
M, SpeculatorVTy, false, GlobalValue::LinkageTypes::ExternalLinkage,
nullptr, "__orc_speculator");
IRBuilder<> Mutator(MContext);
// QueryAnalysis allowed to transform the IR source, one such example is
// Simplify CFG helps the static branch prediction heuristics!
for (auto &Fn : M.getFunctionList()) {
if (!Fn.isDeclaration()) {
auto IRNames = QueryAnalysis(Fn);
// Instrument and register if Query has result
if (IRNames.hasValue()) {
// Emit globals for each function.
auto LoadValueTy = Type::getInt8Ty(MContext);
auto SpeculatorGuard = new GlobalVariable(
M, LoadValueTy, false, GlobalValue::LinkageTypes::InternalLinkage,
ConstantInt::get(LoadValueTy, 0),
"__orc_speculate.guard.for." + Fn.getName());
SpeculatorGuard->setAlignment(Align::None());
SpeculatorGuard->setUnnamedAddr(GlobalValue::UnnamedAddr::Local);
BasicBlock &ProgramEntry = Fn.getEntryBlock();
// Create BasicBlocks before the program's entry basicblock
BasicBlock *SpeculateBlock = BasicBlock::Create(
MContext, "__orc_speculate.block", &Fn, &ProgramEntry);
BasicBlock *SpeculateDecisionBlock = BasicBlock::Create(
MContext, "__orc_speculate.decision.block", &Fn, SpeculateBlock);
assert(SpeculateDecisionBlock == &Fn.getEntryBlock() &&
"SpeculateDecisionBlock not updated?");
Mutator.SetInsertPoint(SpeculateDecisionBlock);
auto LoadGuard =
Mutator.CreateLoad(LoadValueTy, SpeculatorGuard, "guard.value");
// if just loaded value equal to 0,return true.
auto CanSpeculate =
Mutator.CreateICmpEQ(LoadGuard, ConstantInt::get(LoadValueTy, 0),
"compare.to.speculate");
Mutator.CreateCondBr(CanSpeculate, SpeculateBlock, &ProgramEntry);
Mutator.SetInsertPoint(SpeculateBlock);
auto ImplAddrToUint =
Mutator.CreatePtrToInt(&Fn, Type::getInt64Ty(MContext));
Mutator.CreateCall(RuntimeCallTy, RuntimeCall,
{SpeclAddr, ImplAddrToUint});
Mutator.CreateStore(ConstantInt::get(LoadValueTy, 1),
SpeculatorGuard);
Mutator.CreateBr(&ProgramEntry);
assert(Mutator.GetInsertBlock()->getParent() == &Fn &&
"IR builder association mismatch?");
S.registerSymbols(internToJITSymbols(IRNames.getValue()),
&R.getTargetJITDylib());
}
}
}
});
assert(!TSM.withModuleDo([](const Module &M) { return verifyModule(M); }) &&
"Speculation Instrumentation breaks IR?");
NextLayer.emit(std::move(R), std::move(TSM));
}
} // namespace orc
} // namespace llvm
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