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/IR/Argument.h"
  26 #include "llvm/IR/BasicBlock.h"
  27 #include "llvm/IR/Constants.h"
  28 #include "llvm/IR/DerivedTypes.h"
  29 #include "llvm/IR/Function.h"
  30 #include "llvm/IR/InstrTypes.h"
  31 #include "llvm/IR/Instruction.h"
  32 #include "llvm/IR/Instructions.h"
  33 #include "llvm/IR/LLVMContext.h"
  34 #include "llvm/IR/Module.h"
  35 #include "llvm/IR/Type.h"
  36 #include "llvm/Support/Casting.h"
  37 #include "llvm/Support/TargetSelect.h"
  38 #include <algorithm>
  39 #include <cassert>
  40 #include <cstddef>
  41 #include <cstdint>
  42 #include <iostream>
  43 #include <memory>
  44 #include <vector>
  45 #include <pthread.h>
  46
  47 using namespace llvm;
  48
  49 static Function* createAdd1(Module *M) {
  50   LLVMContext &Context = M->getContext();
  51   // Create the add1 function entry and insert this entry into module M.  The
  52   // function will have a return type of "int" and take an argument of "int".
  53   Function *Add1F =
  54       Function::Create(FunctionType::get(Type::getInt32Ty(Context),
  55                                          {Type::getInt32Ty(Context)}, false),
  56                        Function::ExternalLinkage, "add1", M);
  57
  58   // Add a basic block to the function. As before, it automatically inserts
  59   // because of the last argument.
  60   BasicBlock *BB = BasicBlock::Create(Context, "EntryBlock", Add1F);
  61
  62   // Get pointers to the constant `1'.
  63   Value *One = ConstantInt::get(Type::getInt32Ty(Context), 1);
  64
  65   // Get pointers to the integer argument of the add1 function...
  66   assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
  67   Argument *ArgX = &*Add1F->arg_begin();          // Get the arg
  68   ArgX->setName("AnArg");            // Give it a nice symbolic name for fun.
  69
  70   // Create the add instruction, inserting it into the end of BB.
  71   Instruction *Add = BinaryOperator::CreateAdd(One, ArgX, "addresult", BB);
  72
  73   // Create the return instruction and add it to the basic block
  74   ReturnInst::Create(Context, Add, BB);
  75
  76   // Now, function add1 is ready.
  77   return Add1F;
  78 }
  79
  80 static Function *CreateFibFunction(Module *M) {
  81   LLVMContext &Context = M->getContext();
  82   // Create the fib function and insert it into module M.  This function is said
  83   // to return an int and take an int parameter.
  84   FunctionType *FibFTy = FunctionType::get(Type::getInt32Ty(Context),
  85                                            {Type::getInt32Ty(Context)}, false);
  86   Function *FibF =
  87       Function::Create(FibFTy, Function::ExternalLinkage, "fib", M);
  88
  89   // Add a basic block to the function.
  90   BasicBlock *BB = BasicBlock::Create(Context, "EntryBlock", FibF);
  91
  92   // Get pointers to the constants.
  93   Value *One = ConstantInt::get(Type::getInt32Ty(Context), 1);
  94   Value *Two = ConstantInt::get(Type::getInt32Ty(Context), 2);
  95
  96   // Get pointer to the integer argument of the add1 function...
  97   Argument *ArgX = &*FibF->arg_begin(); // Get the arg.
  98   ArgX->setName("AnArg");            // Give it a nice symbolic name for fun.
  99
 100   // Create the true_block.
 101   BasicBlock *RetBB = BasicBlock::Create(Context, "return", FibF);
 102   // Create an exit block.
 103   BasicBlock *RecurseBB = BasicBlock::Create(Context, "recurse", FibF);
 104
 105   // Create the "if (arg < 2) goto exitbb"
 106   Value *CondInst = new ICmpInst(*BB, ICmpInst::ICMP_SLE, ArgX, Two, "cond");
 107   BranchInst::Create(RetBB, RecurseBB, CondInst, BB);
 108
 109   // Create: ret int 1
 110   ReturnInst::Create(Context, One, RetBB);
 111
 112   // create fib(x-1)
 113   Value *Sub = BinaryOperator::CreateSub(ArgX, One, "arg", RecurseBB);
 114   Value *CallFibX1 = CallInst::Create(FibF, Sub, "fibx1", RecurseBB);
 115
 116   // create fib(x-2)
 117   Sub = BinaryOperator::CreateSub(ArgX, Two, "arg", RecurseBB);
 118   Value *CallFibX2 = CallInst::Create(FibF, Sub, "fibx2", RecurseBB);
 119
 120   // fib(x-1)+fib(x-2)
 121   Value *Sum =
 122     BinaryOperator::CreateAdd(CallFibX1, CallFibX2, "addresult", RecurseBB);
 123
 124   // Create the return instruction and add it to the basic block
 125   ReturnInst::Create(Context, Sum, RecurseBB);
 126
 127   return FibF;
 128 }
 129
 130 struct threadParams {
 131   ExecutionEngine* EE;
 132   Function* F;
 133   int value;
 134 };
 135
 136 // We block the subthreads just before they begin to execute:
 137 // we want all of them to call into the JIT at the same time,
 138 // to verify that the locking is working correctly.
 139 class WaitForThreads
 140 {
 141 public:
 142   WaitForThreads()
 143   {
 144     n = 0;
 145     waitFor = 0;
 146
 147     int result = pthread_cond_init( &condition, nullptr );
 148     (void)result;
 149     assert( result == 0 );
 150
 151     result = pthread_mutex_init( &mutex, nullptr );
 152     assert( result == 0 );
 153   }
 154
 155   ~WaitForThreads()
 156   {
 157     int result = pthread_cond_destroy( &condition );
 158     (void)result;
 159     assert( result == 0 );
 160
 161     result = pthread_mutex_destroy( &mutex );
 162     assert( result == 0 );
 163   }
 164
 165   // All threads will stop here until another thread calls releaseThreads
 166   void block()
 167   {
 168     int result = pthread_mutex_lock( &mutex );
 169     (void)result;
 170     assert( result == 0 );
 171     n ++;
 172     //~ std::cout << "block() n " << n << " waitFor " << waitFor << std::endl;
 173
 174     assert( waitFor == 0 || n <= waitFor );
 175     if ( waitFor > 0 && n == waitFor )
 176     {
 177       // There are enough threads blocked that we can release all of them
 178       std::cout << "Unblocking threads from block()" << std::endl;
 179       unblockThreads();
 180     }
 181     else
 182     {
 183       // We just need to wait until someone unblocks us
 184       result = pthread_cond_wait( &condition, &mutex );
 185       assert( result == 0 );
 186     }
 187
 188     // unlock the mutex before returning
 189     result = pthread_mutex_unlock( &mutex );
 190     assert( result == 0 );
 191   }
 192
 193   // If there are num or more threads blocked, it will signal them all
 194   // Otherwise, this thread blocks until there are enough OTHER threads
 195   // blocked
 196   void releaseThreads( size_t num )
 197   {
 198     int result = pthread_mutex_lock( &mutex );
 199     (void)result;
 200     assert( result == 0 );
 201
 202     if ( n >= num ) {
 203       std::cout << "Unblocking threads from releaseThreads()" << std::endl;
 204       unblockThreads();
 205     }
 206     else
 207     {
 208       waitFor = num;
 209       pthread_cond_wait( &condition, &mutex );
 210     }
 211
 212     // unlock the mutex before returning
 213     result = pthread_mutex_unlock( &mutex );
 214     assert( result == 0 );
 215   }
 216
 217 private:
 218   void unblockThreads()
 219   {
 220     // Reset the counters to zero: this way, if any new threads
 221     // enter while threads are exiting, they will block instead
 222     // of triggering a new release of threads
 223     n = 0;
 224
 225     // Reset waitFor to zero: this way, if waitFor threads enter
 226     // while threads are exiting, they will block instead of
 227     // triggering a new release of threads
 228     waitFor = 0;
 229
 230     int result = pthread_cond_broadcast( &condition );
 231     (void)result;
 232     assert(result == 0);
 233   }
 234
 235   size_t n;
 236   size_t waitFor;
 237   pthread_cond_t condition;
 238   pthread_mutex_t mutex;
 239 };
 240
 241 static WaitForThreads synchronize;
 242
 243 void* callFunc( void* param )
 244 {
 245   struct threadParams* p = (struct threadParams*) param;
 246
 247   // Call the `foo' function with no arguments:
 248   std::vector<GenericValue> Args(1);
 249   Args[0].IntVal = APInt(32, p->value);
 250
 251   synchronize.block(); // wait until other threads are at this point
 252   GenericValue gv = p->EE->runFunction(p->F, Args);
 253
 254   return (void*)(intptr_t)gv.IntVal.getZExtValue();
 255 }
 256
 257 int main() {
 258   InitializeNativeTarget();
 259   LLVMContext Context;
 260
 261   // Create some module to put our function into it.
 262   std::unique_ptr<Module> Owner = std::make_unique<Module>("test", Context);
 263   Module *M = Owner.get();
 264
 265   Function* add1F = createAdd1( M );
 266   Function* fibF = CreateFibFunction( M );
 267
 268   // Now we create the JIT.
 269   ExecutionEngine* EE = EngineBuilder(std::move(Owner)).create();
 270
 271   //~ std::cout << "We just constructed this LLVM module:\n\n" << *M;
 272   //~ std::cout << "\n\nRunning foo: " << std::flush;
 273
 274   // Create one thread for add1 and two threads for fib
 275   struct threadParams add1 = { EE, add1F, 1000 };
 276   struct threadParams fib1 = { EE, fibF, 39 };
 277   struct threadParams fib2 = { EE, fibF, 42 };
 278
 279   pthread_t add1Thread;
 280   int result = pthread_create( &add1Thread, nullptr, callFunc, &add1 );
 281   if ( result != 0 ) {
 282           std::cerr << "Could not create thread" << std::endl;
 283           return 1;
 284   }
 285
 286   pthread_t fibThread1;
 287   result = pthread_create( &fibThread1, nullptr, callFunc, &fib1 );
 288   if ( result != 0 ) {
 289           std::cerr << "Could not create thread" << std::endl;
 290           return 1;
 291   }
 292
 293   pthread_t fibThread2;
 294   result = pthread_create( &fibThread2, nullptr, callFunc, &fib2 );
 295   if ( result != 0 ) {
 296           std::cerr << "Could not create thread" << std::endl;
 297           return 1;
 298   }
 299
 300   synchronize.releaseThreads(3); // wait until other threads are at this point
 301
 302   void* returnValue;
 303   result = pthread_join( add1Thread, &returnValue );
 304   if ( result != 0 ) {
 305           std::cerr << "Could not join thread" << std::endl;
 306           return 1;
 307   }
 308   std::cout << "Add1 returned " << intptr_t(returnValue) << std::endl;
 309
 310   result = pthread_join( fibThread1, &returnValue );
 311   if ( result != 0 ) {
 312           std::cerr << "Could not join thread" << std::endl;
 313           return 1;
 314   }
 315   std::cout << "Fib1 returned " << intptr_t(returnValue) << std::endl;
 316
 317   result = pthread_join( fibThread2, &returnValue );
 318   if ( result != 0 ) {
 319           std::cerr << "Could not join thread" << std::endl;
 320           return 1;
 321   }
 322   std::cout << "Fib2 returned " << intptr_t(returnValue) << std::endl;
 323
 324   return 0;
 325 }