llvm/examples/ParallelJIT/ParallelJIT.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-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // Parallel JIT
  10 //
  11 // This test program creates two LLVM functions then calls them from three
  12 // 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 thread
  15 // wakes them up. This complicated work is performed so that all three threads
  16 // call into the JIT at the same time (or the best possible approximation of the
  17 // 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
  48 using namespace llvm;
  49
  50 static Function* createAdd1(Module *M) {
  51   LLVMContext &Context = M->getContext();
  52   // Create the add1 function entry and insert this entry into module M.  The
  53   // 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 inserts
  60   // 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 arg
  68   Argument *ArgX = &*Add1F->arg_begin();          // Get the arg
  69   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 block
  75   ReturnInst::Create(Context, Add, BB);
  76
  77   // Now, function add1 is ready.
  78   return Add1F;
  79 }
  80
  81 static Function *CreateFibFunction(Module *M) {
  82   LLVMContext &Context = M->getContext();
  83   // Create the fib function and insert it into module M.  This function is said
  84   // 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 1
 111   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 block
 126   ReturnInst::Create(Context, Sum, RecurseBB);
 127
 128   return FibF;
 129 }
 130
 131 struct 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.
 140 class WaitForThreads
 141 {
 142 public:
 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 releaseThreads
 167   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 them
 179       std::cout << "Unblocking threads from block()" << std::endl;
 180       unblockThreads();
 181     }
 182     else
 183     {
 184       // We just need to wait until someone unblocks us
 185       result = pthread_cond_wait( &condition, &mutex );
 186       assert( result == 0 );
 187     }
 188
 189     // unlock the mutex before returning
 190     result = pthread_mutex_unlock( &mutex );
 191     assert( result == 0 );
 192   }
 193
 194   // If there are num or more threads blocked, it will signal them all
 195   // Otherwise, this thread blocks until there are enough OTHER threads
 196   // blocked
 197   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     else
 208     {
 209       waitFor = num;
 210       pthread_cond_wait( &condition, &mutex );
 211     }
 212
 213     // unlock the mutex before returning
 214     result = pthread_mutex_unlock( &mutex );
 215     assert( result == 0 );
 216   }
 217
 218 private:
 219   void unblockThreads()
 220   {
 221     // Reset the counters to zero: this way, if any new threads
 222     // enter while threads are exiting, they will block instead
 223     // of triggering a new release of threads
 224     n = 0;
 225
 226     // Reset waitFor to zero: this way, if waitFor threads enter
 227     // while threads are exiting, they will block instead of
 228     // triggering a new release of threads
 229     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
 242 static WaitForThreads synchronize;
 243
 244 void* 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 point
 253   GenericValue gv = p->EE->runFunction(p->F, Args);
 254
 255   return (void*)(intptr_t)gv.IntVal.getZExtValue();
 256 }
 257
 258 int 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 fib
 277   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 point
 303
 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 }