328 lines · cpp
1//===-- examples/ParallelJIT/ParallelJIT.cpp - Exercise threaded-safe JIT -===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// Parallel JIT10//11// This test program creates two LLVM functions then calls them from three12// separate threads. It requires the pthreads library.13// The three threads are created and then block waiting on a condition variable.14// Once all threads are blocked on the conditional variable, the main thread15// wakes them up. This complicated work is performed so that all three threads16// call into the JIT at the same time (or the best possible approximation of the17// same time). This test had assertion errors until I got the locking right.18//19//===----------------------------------------------------------------------===//20 21#include "llvm/ADT/APInt.h"22#include "llvm/ADT/STLExtras.h"23#include "llvm/ExecutionEngine/ExecutionEngine.h"24#include "llvm/ExecutionEngine/GenericValue.h"25#include "llvm/ExecutionEngine/MCJIT.h"26#include "llvm/IR/Argument.h"27#include "llvm/IR/BasicBlock.h"28#include "llvm/IR/Constants.h"29#include "llvm/IR/DerivedTypes.h"30#include "llvm/IR/Function.h"31#include "llvm/IR/InstrTypes.h"32#include "llvm/IR/Instruction.h"33#include "llvm/IR/Instructions.h"34#include "llvm/IR/LLVMContext.h"35#include "llvm/IR/Module.h"36#include "llvm/IR/Type.h"37#include "llvm/Support/Casting.h"38#include "llvm/Support/TargetSelect.h"39#include <algorithm>40#include <cassert>41#include <cstddef>42#include <cstdint>43#include <iostream>44#include <memory>45#include <vector>46#include <pthread.h>47 48using namespace llvm;49 50static Function* createAdd1(Module *M) {51 LLVMContext &Context = M->getContext();52 // Create the add1 function entry and insert this entry into module M. The53 // function will have a return type of "int" and take an argument of "int".54 Function *Add1F =55 Function::Create(FunctionType::get(Type::getInt32Ty(Context),56 {Type::getInt32Ty(Context)}, false),57 Function::ExternalLinkage, "add1", M);58 59 // Add a basic block to the function. As before, it automatically inserts60 // because of the last argument.61 BasicBlock *BB = BasicBlock::Create(Context, "EntryBlock", Add1F);62 63 // Get pointers to the constant `1'.64 Value *One = ConstantInt::get(Type::getInt32Ty(Context), 1);65 66 // Get pointers to the integer argument of the add1 function...67 assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg68 Argument *ArgX = &*Add1F->arg_begin(); // Get the arg69 ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.70 71 // Create the add instruction, inserting it into the end of BB.72 Instruction *Add = BinaryOperator::CreateAdd(One, ArgX, "addresult", BB);73 74 // Create the return instruction and add it to the basic block75 ReturnInst::Create(Context, Add, BB);76 77 // Now, function add1 is ready.78 return Add1F;79}80 81static Function *CreateFibFunction(Module *M) {82 LLVMContext &Context = M->getContext();83 // Create the fib function and insert it into module M. This function is said84 // to return an int and take an int parameter.85 FunctionType *FibFTy = FunctionType::get(Type::getInt32Ty(Context),86 {Type::getInt32Ty(Context)}, false);87 Function *FibF =88 Function::Create(FibFTy, Function::ExternalLinkage, "fib", M);89 90 // Add a basic block to the function.91 BasicBlock *BB = BasicBlock::Create(Context, "EntryBlock", FibF);92 93 // Get pointers to the constants.94 Value *One = ConstantInt::get(Type::getInt32Ty(Context), 1);95 Value *Two = ConstantInt::get(Type::getInt32Ty(Context), 2);96 97 // Get pointer to the integer argument of the add1 function...98 Argument *ArgX = &*FibF->arg_begin(); // Get the arg.99 ArgX->setName("AnArg"); // Give it a nice symbolic name for fun.100 101 // Create the true_block.102 BasicBlock *RetBB = BasicBlock::Create(Context, "return", FibF);103 // Create an exit block.104 BasicBlock *RecurseBB = BasicBlock::Create(Context, "recurse", FibF);105 106 // Create the "if (arg < 2) goto exitbb"107 Value *CondInst = new ICmpInst(BB, ICmpInst::ICMP_SLE, ArgX, Two, "cond");108 BranchInst::Create(RetBB, RecurseBB, CondInst, BB);109 110 // Create: ret int 1111 ReturnInst::Create(Context, One, RetBB);112 113 // create fib(x-1)114 Value *Sub = BinaryOperator::CreateSub(ArgX, One, "arg", RecurseBB);115 Value *CallFibX1 = CallInst::Create(FibF, Sub, "fibx1", RecurseBB);116 117 // create fib(x-2)118 Sub = BinaryOperator::CreateSub(ArgX, Two, "arg", RecurseBB);119 Value *CallFibX2 = CallInst::Create(FibF, Sub, "fibx2", RecurseBB);120 121 // fib(x-1)+fib(x-2)122 Value *Sum =123 BinaryOperator::CreateAdd(CallFibX1, CallFibX2, "addresult", RecurseBB);124 125 // Create the return instruction and add it to the basic block126 ReturnInst::Create(Context, Sum, RecurseBB);127 128 return FibF;129}130 131struct threadParams {132 ExecutionEngine* EE;133 Function* F;134 int value;135};136 137// We block the subthreads just before they begin to execute:138// we want all of them to call into the JIT at the same time,139// to verify that the locking is working correctly.140class WaitForThreads141{142public:143 WaitForThreads()144 {145 n = 0;146 waitFor = 0;147 148 int result = pthread_cond_init( &condition, nullptr );149 (void)result;150 assert( result == 0 );151 152 result = pthread_mutex_init( &mutex, nullptr );153 assert( result == 0 );154 }155 156 ~WaitForThreads()157 {158 int result = pthread_cond_destroy( &condition );159 (void)result;160 assert( result == 0 );161 162 result = pthread_mutex_destroy( &mutex );163 assert( result == 0 );164 }165 166 // All threads will stop here until another thread calls releaseThreads167 void block()168 {169 int result = pthread_mutex_lock( &mutex );170 (void)result;171 assert( result == 0 );172 n ++;173 //~ std::cout << "block() n " << n << " waitFor " << waitFor << std::endl;174 175 assert( waitFor == 0 || n <= waitFor );176 if ( waitFor > 0 && n == waitFor )177 {178 // There are enough threads blocked that we can release all of them179 std::cout << "Unblocking threads from block()" << std::endl;180 unblockThreads();181 }182 else183 {184 // We just need to wait until someone unblocks us185 result = pthread_cond_wait( &condition, &mutex );186 assert( result == 0 );187 }188 189 // unlock the mutex before returning190 result = pthread_mutex_unlock( &mutex );191 assert( result == 0 );192 }193 194 // If there are num or more threads blocked, it will signal them all195 // Otherwise, this thread blocks until there are enough OTHER threads196 // blocked197 void releaseThreads( size_t num )198 {199 int result = pthread_mutex_lock( &mutex );200 (void)result;201 assert( result == 0 );202 203 if ( n >= num ) {204 std::cout << "Unblocking threads from releaseThreads()" << std::endl;205 unblockThreads();206 }207 else208 {209 waitFor = num;210 pthread_cond_wait( &condition, &mutex );211 }212 213 // unlock the mutex before returning214 result = pthread_mutex_unlock( &mutex );215 assert( result == 0 );216 }217 218private:219 void unblockThreads()220 {221 // Reset the counters to zero: this way, if any new threads222 // enter while threads are exiting, they will block instead223 // of triggering a new release of threads224 n = 0;225 226 // Reset waitFor to zero: this way, if waitFor threads enter227 // while threads are exiting, they will block instead of228 // triggering a new release of threads229 waitFor = 0;230 231 int result = pthread_cond_broadcast( &condition );232 (void)result;233 assert(result == 0);234 }235 236 size_t n;237 size_t waitFor;238 pthread_cond_t condition;239 pthread_mutex_t mutex;240};241 242static WaitForThreads synchronize;243 244void* callFunc( void* param )245{246 struct threadParams* p = (struct threadParams*) param;247 248 // Call the `foo' function with no arguments:249 std::vector<GenericValue> Args(1);250 Args[0].IntVal = APInt(32, p->value);251 252 synchronize.block(); // wait until other threads are at this point253 GenericValue gv = p->EE->runFunction(p->F, Args);254 255 return (void*)(intptr_t)gv.IntVal.getZExtValue();256}257 258int main() {259 InitializeNativeTarget();260 LLVMInitializeNativeAsmPrinter();261 LLVMContext Context;262 263 // Create some module to put our function into it.264 std::unique_ptr<Module> Owner = std::make_unique<Module>("test", Context);265 Module *M = Owner.get();266 267 Function* add1F = createAdd1( M );268 Function* fibF = CreateFibFunction( M );269 270 // Now we create the JIT.271 ExecutionEngine* EE = EngineBuilder(std::move(Owner)).create();272 273 //~ std::cout << "We just constructed this LLVM module:\n\n" << *M;274 //~ std::cout << "\n\nRunning foo: " << std::flush;275 276 // Create one thread for add1 and two threads for fib277 struct threadParams add1 = { EE, add1F, 1000 };278 struct threadParams fib1 = { EE, fibF, 39 };279 struct threadParams fib2 = { EE, fibF, 42 };280 281 pthread_t add1Thread;282 int result = pthread_create( &add1Thread, nullptr, callFunc, &add1 );283 if ( result != 0 ) {284 std::cerr << "Could not create thread" << std::endl;285 return 1;286 }287 288 pthread_t fibThread1;289 result = pthread_create( &fibThread1, nullptr, callFunc, &fib1 );290 if ( result != 0 ) {291 std::cerr << "Could not create thread" << std::endl;292 return 1;293 }294 295 pthread_t fibThread2;296 result = pthread_create( &fibThread2, nullptr, callFunc, &fib2 );297 if ( result != 0 ) {298 std::cerr << "Could not create thread" << std::endl;299 return 1;300 }301 302 synchronize.releaseThreads(3); // wait until other threads are at this point303 304 void* returnValue;305 result = pthread_join( add1Thread, &returnValue );306 if ( result != 0 ) {307 std::cerr << "Could not join thread" << std::endl;308 return 1;309 }310 std::cout << "Add1 returned " << intptr_t(returnValue) << std::endl;311 312 result = pthread_join( fibThread1, &returnValue );313 if ( result != 0 ) {314 std::cerr << "Could not join thread" << std::endl;315 return 1;316 }317 std::cout << "Fib1 returned " << intptr_t(returnValue) << std::endl;318 319 result = pthread_join( fibThread2, &returnValue );320 if ( result != 0 ) {321 std::cerr << "Could not join thread" << std::endl;322 return 1;323 }324 std::cout << "Fib2 returned " << intptr_t(returnValue) << std::endl;325 326 return 0;327}328