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//===-- JIT.cpp - LLVM Just in Time Compiler ------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This tool implements a just-in-time compiler for LLVM, allowing direct
// execution of LLVM bytecode in an efficient manner.
//
//===----------------------------------------------------------------------===//
#include "JIT.h"
#include "llvm/Function.h"
#include "llvm/ModuleProvider.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/ExecutionEngine/GenericValue.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetJITInfo.h"
using namespace llvm;
JIT::JIT(ModuleProvider *MP, TargetMachine &tm, TargetJITInfo &tji)
: ExecutionEngine(MP), TM(tm), TJI(tji), PM(MP) {
setTargetData(TM.getTargetData());
// Initialize MCE
MCE = createEmitter(*this);
// Compile LLVM Code down to machine code in the intermediate representation
TJI.addPassesToJITCompile(PM);
// Turn the machine code intermediate representation into bytes in memory that
// may be executed.
if (TM.addPassesToEmitMachineCode(PM, *MCE)) {
std::cerr << "lli: target '" << TM.getName()
<< "' doesn't support machine code emission!\n";
abort();
}
emitGlobals();
}
JIT::~JIT() {
delete MCE;
delete &TM;
}
/// run - Start execution with the specified function and arguments.
///
GenericValue JIT::run(Function *F, const std::vector<GenericValue> &ArgValues) {
assert (F && "Function *F was null at entry to run()");
int (*PF)(int, char **, const char **) =
(int(*)(int, char **, const char **))getPointerToFunction(F);
assert(PF != 0 && "Pointer to fn's code was null after getPointerToFunction");
// Call the function.
int ExitCode = PF(ArgValues[0].IntVal, (char **) GVTOP (ArgValues[1]),
(const char **) GVTOP (ArgValues[2]));
// Run any atexit handlers now!
runAtExitHandlers();
GenericValue rv;
rv.IntVal = ExitCode;
return rv;
}
/// runJITOnFunction - Run the FunctionPassManager full of
/// just-in-time compilation passes on F, hopefully filling in
/// GlobalAddress[F] with the address of F's machine code.
///
void JIT::runJITOnFunction(Function *F) {
static bool isAlreadyCodeGenerating = false;
assert(!isAlreadyCodeGenerating && "Error: Recursive compilation detected!");
// JIT the function
isAlreadyCodeGenerating = true;
PM.run(*F);
isAlreadyCodeGenerating = false;
}
/// getPointerToFunction - This method is used to get the address of the
/// specified function, compiling it if neccesary.
///
void *JIT::getPointerToFunction(Function *F) {
void *&Addr = GlobalAddress[F]; // Check if function already code gen'd
if (Addr) return Addr;
// Make sure we read in the function if it exists in this Module
MP->materializeFunction(F);
if (F->isExternal())
return Addr = getPointerToNamedFunction(F->getName());
runJITOnFunction(F);
assert(Addr && "Code generation didn't add function to GlobalAddress table!");
return Addr;
}
// getPointerToFunctionOrStub - If the specified function has been
// code-gen'd, return a pointer to the function. If not, compile it, or use
// a stub to implement lazy compilation if available.
//
void *JIT::getPointerToFunctionOrStub(Function *F) {
// If we have already code generated the function, just return the address.
std::map<const GlobalValue*, void *>::iterator I = GlobalAddress.find(F);
if (I != GlobalAddress.end()) return I->second;
// If the target supports "stubs" for functions, get a stub now.
if (void *Ptr = TJI.getJITStubForFunction(F, *MCE))
return Ptr;
// Otherwise, if the target doesn't support it, just codegen the function.
return getPointerToFunction(F);
}
/// recompileAndRelinkFunction - This method is used to force a function
/// which has already been compiled, to be compiled again, possibly
/// after it has been modified. Then the entry to the old copy is overwritten
/// with a branch to the new copy. If there was no old copy, this acts
/// just like JIT::getPointerToFunction().
///
void *JIT::recompileAndRelinkFunction(Function *F) {
void *&Addr = GlobalAddress[F]; // Check if function already code gen'd
// If it's not already compiled (this is kind of weird) there is no
// reason to patch it up.
if (!Addr) { return getPointerToFunction (F); }
void *OldAddr = Addr;
Addr = 0;
MachineFunction::destruct(F);
runJITOnFunction(F);
assert(Addr && "Code generation didn't add function to GlobalAddress table!");
TJI.replaceMachineCodeForFunction(OldAddr, Addr);
return Addr;
}
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