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1 //===-- examples/ParallelJIT/ParallelJIT.cpp - Exercise threaded-safe JIT -===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Parallel JIT
11 //
12 // This test program creates two LLVM functions then calls them from three
13 // separate threads.  It requires the pthreads library.
14 // The three threads are created and then block waiting on a condition variable.
15 // Once all threads are blocked on the conditional variable, the main thread
16 // wakes them up. This complicated work is performed so that all three threads
17 // call into the JIT at the same time (or the best possible approximation of the
18 // same time). This test had assertion errors until I got the locking right.
19 
20 #include <pthread.h>
21 #include "llvm/LLVMContext.h"
22 #include "llvm/Module.h"
23 #include "llvm/Constants.h"
24 #include "llvm/DerivedTypes.h"
25 #include "llvm/Instructions.h"
26 #include "llvm/ExecutionEngine/JIT.h"
27 #include "llvm/ExecutionEngine/Interpreter.h"
28 #include "llvm/ExecutionEngine/GenericValue.h"
29 #include "llvm/Support/TargetSelect.h"
30 #include <iostream>
31 using namespace llvm;
32 
createAdd1(Module * M)33 static Function* createAdd1(Module *M) {
34   // Create the add1 function entry and insert this entry into module M.  The
35   // function will have a return type of "int" and take an argument of "int".
36   // The '0' terminates the list of argument types.
37   Function *Add1F =
38     cast<Function>(M->getOrInsertFunction("add1",
39                                           Type::getInt32Ty(M->getContext()),
40                                           Type::getInt32Ty(M->getContext()),
41                                           (Type *)0));
42 
43   // Add a basic block to the function. As before, it automatically inserts
44   // because of the last argument.
45   BasicBlock *BB = BasicBlock::Create(M->getContext(), "EntryBlock", Add1F);
46 
47   // Get pointers to the constant `1'.
48   Value *One = ConstantInt::get(Type::getInt32Ty(M->getContext()), 1);
49 
50   // Get pointers to the integer argument of the add1 function...
51   assert(Add1F->arg_begin() != Add1F->arg_end()); // Make sure there's an arg
52   Argument *ArgX = Add1F->arg_begin();  // Get the arg
53   ArgX->setName("AnArg");            // Give it a nice symbolic name for fun.
54 
55   // Create the add instruction, inserting it into the end of BB.
56   Instruction *Add = BinaryOperator::CreateAdd(One, ArgX, "addresult", BB);
57 
58   // Create the return instruction and add it to the basic block
59   ReturnInst::Create(M->getContext(), Add, BB);
60 
61   // Now, function add1 is ready.
62   return Add1F;
63 }
64 
CreateFibFunction(Module * M)65 static Function *CreateFibFunction(Module *M) {
66   // Create the fib function and insert it into module M.  This function is said
67   // to return an int and take an int parameter.
68   Function *FibF =
69     cast<Function>(M->getOrInsertFunction("fib",
70                                           Type::getInt32Ty(M->getContext()),
71                                           Type::getInt32Ty(M->getContext()),
72                                           (Type *)0));
73 
74   // Add a basic block to the function.
75   BasicBlock *BB = BasicBlock::Create(M->getContext(), "EntryBlock", FibF);
76 
77   // Get pointers to the constants.
78   Value *One = ConstantInt::get(Type::getInt32Ty(M->getContext()), 1);
79   Value *Two = ConstantInt::get(Type::getInt32Ty(M->getContext()), 2);
80 
81   // Get pointer to the integer argument of the add1 function...
82   Argument *ArgX = FibF->arg_begin();   // Get the arg.
83   ArgX->setName("AnArg");            // Give it a nice symbolic name for fun.
84 
85   // Create the true_block.
86   BasicBlock *RetBB = BasicBlock::Create(M->getContext(), "return", FibF);
87   // Create an exit block.
88   BasicBlock* RecurseBB = BasicBlock::Create(M->getContext(), "recurse", FibF);
89 
90   // Create the "if (arg < 2) goto exitbb"
91   Value *CondInst = new ICmpInst(*BB, ICmpInst::ICMP_SLE, ArgX, Two, "cond");
92   BranchInst::Create(RetBB, RecurseBB, CondInst, BB);
93 
94   // Create: ret int 1
95   ReturnInst::Create(M->getContext(), One, RetBB);
96 
97   // create fib(x-1)
98   Value *Sub = BinaryOperator::CreateSub(ArgX, One, "arg", RecurseBB);
99   Value *CallFibX1 = CallInst::Create(FibF, Sub, "fibx1", RecurseBB);
100 
101   // create fib(x-2)
102   Sub = BinaryOperator::CreateSub(ArgX, Two, "arg", RecurseBB);
103   Value *CallFibX2 = CallInst::Create(FibF, Sub, "fibx2", RecurseBB);
104 
105   // fib(x-1)+fib(x-2)
106   Value *Sum =
107     BinaryOperator::CreateAdd(CallFibX1, CallFibX2, "addresult", RecurseBB);
108 
109   // Create the return instruction and add it to the basic block
110   ReturnInst::Create(M->getContext(), Sum, RecurseBB);
111 
112   return FibF;
113 }
114 
115 struct threadParams {
116   ExecutionEngine* EE;
117   Function* F;
118   int value;
119 };
120 
121 // We block the subthreads just before they begin to execute:
122 // we want all of them to call into the JIT at the same time,
123 // to verify that the locking is working correctly.
124 class WaitForThreads
125 {
126 public:
WaitForThreads()127   WaitForThreads()
128   {
129     n = 0;
130     waitFor = 0;
131 
132     int result = pthread_cond_init( &condition, NULL );
133     assert( result == 0 );
134 
135     result = pthread_mutex_init( &mutex, NULL );
136     assert( result == 0 );
137   }
138 
~WaitForThreads()139   ~WaitForThreads()
140   {
141     int result = pthread_cond_destroy( &condition );
142     assert( result == 0 );
143 
144     result = pthread_mutex_destroy( &mutex );
145     assert( result == 0 );
146   }
147 
148   // All threads will stop here until another thread calls releaseThreads
block()149   void block()
150   {
151     int result = pthread_mutex_lock( &mutex );
152     assert( result == 0 );
153     n ++;
154     //~ std::cout << "block() n " << n << " waitFor " << waitFor << std::endl;
155 
156     assert( waitFor == 0 || n <= waitFor );
157     if ( waitFor > 0 && n == waitFor )
158     {
159       // There are enough threads blocked that we can release all of them
160       std::cout << "Unblocking threads from block()" << std::endl;
161       unblockThreads();
162     }
163     else
164     {
165       // We just need to wait until someone unblocks us
166       result = pthread_cond_wait( &condition, &mutex );
167       assert( result == 0 );
168     }
169 
170     // unlock the mutex before returning
171     result = pthread_mutex_unlock( &mutex );
172     assert( result == 0 );
173   }
174 
175   // If there are num or more threads blocked, it will signal them all
176   // Otherwise, this thread blocks until there are enough OTHER threads
177   // blocked
releaseThreads(size_t num)178   void releaseThreads( size_t num )
179   {
180     int result = pthread_mutex_lock( &mutex );
181     assert( result == 0 );
182 
183     if ( n >= num ) {
184       std::cout << "Unblocking threads from releaseThreads()" << std::endl;
185       unblockThreads();
186     }
187     else
188     {
189       waitFor = num;
190       pthread_cond_wait( &condition, &mutex );
191     }
192 
193     // unlock the mutex before returning
194     result = pthread_mutex_unlock( &mutex );
195     assert( result == 0 );
196   }
197 
198 private:
unblockThreads()199   void unblockThreads()
200   {
201     // Reset the counters to zero: this way, if any new threads
202     // enter while threads are exiting, they will block instead
203     // of triggering a new release of threads
204     n = 0;
205 
206     // Reset waitFor to zero: this way, if waitFor threads enter
207     // while threads are exiting, they will block instead of
208     // triggering a new release of threads
209     waitFor = 0;
210 
211     int result = pthread_cond_broadcast( &condition );
212     (void)result;
213     assert(result == 0);
214   }
215 
216   size_t n;
217   size_t waitFor;
218   pthread_cond_t condition;
219   pthread_mutex_t mutex;
220 };
221 
222 static WaitForThreads synchronize;
223 
callFunc(void * param)224 void* callFunc( void* param )
225 {
226   struct threadParams* p = (struct threadParams*) param;
227 
228   // Call the `foo' function with no arguments:
229   std::vector<GenericValue> Args(1);
230   Args[0].IntVal = APInt(32, p->value);
231 
232   synchronize.block(); // wait until other threads are at this point
233   GenericValue gv = p->EE->runFunction(p->F, Args);
234 
235   return (void*)(intptr_t)gv.IntVal.getZExtValue();
236 }
237 
main()238 int main() {
239   InitializeNativeTarget();
240   LLVMContext Context;
241 
242   // Create some module to put our function into it.
243   Module *M = new Module("test", Context);
244 
245   Function* add1F = createAdd1( M );
246   Function* fibF = CreateFibFunction( M );
247 
248   // Now we create the JIT.
249   ExecutionEngine* EE = EngineBuilder(M).create();
250 
251   //~ std::cout << "We just constructed this LLVM module:\n\n" << *M;
252   //~ std::cout << "\n\nRunning foo: " << std::flush;
253 
254   // Create one thread for add1 and two threads for fib
255   struct threadParams add1 = { EE, add1F, 1000 };
256   struct threadParams fib1 = { EE, fibF, 39 };
257   struct threadParams fib2 = { EE, fibF, 42 };
258 
259   pthread_t add1Thread;
260   int result = pthread_create( &add1Thread, NULL, callFunc, &add1 );
261   if ( result != 0 ) {
262           std::cerr << "Could not create thread" << std::endl;
263           return 1;
264   }
265 
266   pthread_t fibThread1;
267   result = pthread_create( &fibThread1, NULL, callFunc, &fib1 );
268   if ( result != 0 ) {
269           std::cerr << "Could not create thread" << std::endl;
270           return 1;
271   }
272 
273   pthread_t fibThread2;
274   result = pthread_create( &fibThread2, NULL, callFunc, &fib2 );
275   if ( result != 0 ) {
276           std::cerr << "Could not create thread" << std::endl;
277           return 1;
278   }
279 
280   synchronize.releaseThreads(3); // wait until other threads are at this point
281 
282   void* returnValue;
283   result = pthread_join( add1Thread, &returnValue );
284   if ( result != 0 ) {
285           std::cerr << "Could not join thread" << std::endl;
286           return 1;
287   }
288   std::cout << "Add1 returned " << intptr_t(returnValue) << std::endl;
289 
290   result = pthread_join( fibThread1, &returnValue );
291   if ( result != 0 ) {
292           std::cerr << "Could not join thread" << std::endl;
293           return 1;
294   }
295   std::cout << "Fib1 returned " << intptr_t(returnValue) << std::endl;
296 
297   result = pthread_join( fibThread2, &returnValue );
298   if ( result != 0 ) {
299           std::cerr << "Could not join thread" << std::endl;
300           return 1;
301   }
302   std::cout << "Fib2 returned " << intptr_t(returnValue) << std::endl;
303 
304   return 0;
305 }
306