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b35b30c283
leaked to the system. Now they are destroyed with the JITMemoryManager is destroyed. llvm-svn: 19434
448 lines
16 KiB
C++
448 lines
16 KiB
C++
//===-- JITEmitter.cpp - Write machine code to executable memory ----------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file was developed by the LLVM research group and is distributed under
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// the University of Illinois Open Source License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines a MachineCodeEmitter object that is used by the JIT to
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// write machine code to memory and remember where relocatable values are.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "jit"
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#include "JIT.h"
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#include "llvm/Constant.h"
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#include "llvm/Module.h"
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#include "llvm/CodeGen/MachineCodeEmitter.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineConstantPool.h"
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#include "llvm/CodeGen/MachineRelocation.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Target/TargetJITInfo.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/System/Memory.h"
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using namespace llvm;
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namespace {
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Statistic<> NumBytes("jit", "Number of bytes of machine code compiled");
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JIT *TheJIT = 0;
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}
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//===----------------------------------------------------------------------===//
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// JITMemoryManager code.
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//
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namespace {
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/// JITMemoryManager - Manage memory for the JIT code generation in a logical,
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/// sane way. This splits a large block of MAP_NORESERVE'd memory into two
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/// sections, one for function stubs, one for the functions themselves. We
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/// have to do this because we may need to emit a function stub while in the
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/// middle of emitting a function, and we don't know how large the function we
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/// are emitting is. This never bothers to release the memory, because when
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/// we are ready to destroy the JIT, the program exits.
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class JITMemoryManager {
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sys::MemoryBlock MemBlock; // Virtual memory block allocated RWX
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unsigned char *MemBase; // Base of block of memory, start of stub mem
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unsigned char *FunctionBase; // Start of the function body area
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unsigned char *ConstantPool; // Memory allocated for constant pools
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unsigned char *CurStubPtr, *CurFunctionPtr, *CurConstantPtr;
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public:
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JITMemoryManager();
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~JITMemoryManager();
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inline unsigned char *allocateStub(unsigned StubSize);
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inline unsigned char *allocateConstant(unsigned ConstantSize,
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unsigned Alignment);
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inline unsigned char *startFunctionBody();
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inline void endFunctionBody(unsigned char *FunctionEnd);
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};
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}
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JITMemoryManager::JITMemoryManager() {
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// Allocate a 16M block of memory...
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MemBlock = sys::Memory::AllocateRWX((16 << 20));
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MemBase = reinterpret_cast<unsigned char*>(MemBlock.base());
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FunctionBase = MemBase + 512*1024; // Use 512k for stubs
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// Allocate stubs backwards from the function base, allocate functions forward
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// from the function base.
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CurStubPtr = CurFunctionPtr = FunctionBase;
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ConstantPool = new unsigned char [512*1024]; // Use 512k for constant pools
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CurConstantPtr = ConstantPool + 512*1024;
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}
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JITMemoryManager::~JITMemoryManager() {
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sys::Memory::ReleaseRWX(MemBlock);
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delete[] ConstantPool;
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}
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unsigned char *JITMemoryManager::allocateStub(unsigned StubSize) {
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CurStubPtr -= StubSize;
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if (CurStubPtr < MemBase) {
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std::cerr << "JIT ran out of memory for function stubs!\n";
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abort();
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}
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return CurStubPtr;
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}
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unsigned char *JITMemoryManager::allocateConstant(unsigned ConstantSize,
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unsigned Alignment) {
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// Reserve space and align pointer.
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CurConstantPtr -= ConstantSize;
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CurConstantPtr =
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(unsigned char *)((intptr_t)CurConstantPtr & ~((intptr_t)Alignment - 1));
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if (CurConstantPtr < ConstantPool) {
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std::cerr << "JIT ran out of memory for constant pools!\n";
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abort();
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}
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return CurConstantPtr;
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}
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unsigned char *JITMemoryManager::startFunctionBody() {
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// Round up to an even multiple of 8 bytes, this should eventually be target
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// specific.
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return (unsigned char*)(((intptr_t)CurFunctionPtr + 7) & ~7);
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}
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void JITMemoryManager::endFunctionBody(unsigned char *FunctionEnd) {
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assert(FunctionEnd > CurFunctionPtr);
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CurFunctionPtr = FunctionEnd;
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}
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//===----------------------------------------------------------------------===//
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// JIT lazy compilation code.
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//
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namespace {
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/// JITResolver - Keep track of, and resolve, call sites for functions that
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/// have not yet been compiled.
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class JITResolver {
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/// MCE - The MachineCodeEmitter to use to emit stubs with.
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MachineCodeEmitter &MCE;
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/// LazyResolverFn - The target lazy resolver function that we actually
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/// rewrite instructions to use.
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TargetJITInfo::LazyResolverFn LazyResolverFn;
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// FunctionToStubMap - Keep track of the stub created for a particular
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// function so that we can reuse them if necessary.
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std::map<Function*, void*> FunctionToStubMap;
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// StubToFunctionMap - Keep track of the function that each stub corresponds
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// to.
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std::map<void*, Function*> StubToFunctionMap;
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public:
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JITResolver(MachineCodeEmitter &mce) : MCE(mce) {
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LazyResolverFn =
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TheJIT->getJITInfo().getLazyResolverFunction(JITCompilerFn);
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}
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/// getFunctionStub - This returns a pointer to a function stub, creating
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/// one on demand as needed.
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void *getFunctionStub(Function *F);
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/// AddCallbackAtLocation - If the target is capable of rewriting an
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/// instruction without the use of a stub, record the location of the use so
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/// we know which function is being used at the location.
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void *AddCallbackAtLocation(Function *F, void *Location) {
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/// Get the target-specific JIT resolver function.
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StubToFunctionMap[Location] = F;
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return (void*)LazyResolverFn;
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}
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/// JITCompilerFn - This function is called to resolve a stub to a compiled
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/// address. If the LLVM Function corresponding to the stub has not yet
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/// been compiled, this function compiles it first.
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static void *JITCompilerFn(void *Stub);
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};
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}
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/// getJITResolver - This function returns the one instance of the JIT resolver.
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///
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static JITResolver &getJITResolver(MachineCodeEmitter *MCE = 0) {
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static JITResolver TheJITResolver(*MCE);
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return TheJITResolver;
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}
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/// getFunctionStub - This returns a pointer to a function stub, creating
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/// one on demand as needed.
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void *JITResolver::getFunctionStub(Function *F) {
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// If we already have a stub for this function, recycle it.
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void *&Stub = FunctionToStubMap[F];
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if (Stub) return Stub;
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// Call the lazy resolver function unless we already KNOW it is an external
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// function, in which case we just skip the lazy resolution step.
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void *Actual = (void*)LazyResolverFn;
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if (F->hasExternalLinkage())
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Actual = TheJIT->getPointerToFunction(F);
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// Otherwise, codegen a new stub. For now, the stub will call the lazy
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// resolver function.
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Stub = TheJIT->getJITInfo().emitFunctionStub(Actual, MCE);
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if (F->hasExternalLinkage()) {
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// If we are getting the stub for an external function, we really want the
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// address of the stub in the GlobalAddressMap for the JIT, not the address
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// of the external function.
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TheJIT->updateGlobalMapping(F, Stub);
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}
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DEBUG(std::cerr << "JIT: Stub emitted at [" << Stub << "] for function '"
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<< F->getName() << "'\n");
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// Finally, keep track of the stub-to-Function mapping so that the
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// JITCompilerFn knows which function to compile!
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StubToFunctionMap[Stub] = F;
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return Stub;
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}
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/// JITCompilerFn - This function is called when a lazy compilation stub has
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/// been entered. It looks up which function this stub corresponds to, compiles
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/// it if necessary, then returns the resultant function pointer.
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void *JITResolver::JITCompilerFn(void *Stub) {
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JITResolver &JR = getJITResolver();
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// The address given to us for the stub may not be exactly right, it might be
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// a little bit after the stub. As such, use upper_bound to find it.
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std::map<void*, Function*>::iterator I =
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JR.StubToFunctionMap.upper_bound(Stub);
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assert(I != JR.StubToFunctionMap.begin() && "This is not a known stub!");
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Function *F = (--I)->second;
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// The target function will rewrite the stub so that the compilation callback
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// function is no longer called from this stub.
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JR.StubToFunctionMap.erase(I);
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DEBUG(std::cerr << "JIT: Lazily resolving function '" << F->getName()
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<< "' In stub ptr = " << Stub << " actual ptr = "
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<< I->first << "\n");
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void *Result = TheJIT->getPointerToFunction(F);
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// We don't need to reuse this stub in the future, as F is now compiled.
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JR.FunctionToStubMap.erase(F);
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// FIXME: We could rewrite all references to this stub if we knew them.
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return Result;
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}
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// getPointerToFunctionOrStub - If the specified function has been
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// code-gen'd, return a pointer to the function. If not, compile it, or use
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// a stub to implement lazy compilation if available.
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//
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void *JIT::getPointerToFunctionOrStub(Function *F) {
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// If we have already code generated the function, just return the address.
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if (void *Addr = getPointerToGlobalIfAvailable(F))
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return Addr;
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// Get a stub if the target supports it
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return getJITResolver(MCE).getFunctionStub(F);
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}
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//===----------------------------------------------------------------------===//
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// JITEmitter code.
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//
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namespace {
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/// JITEmitter - The JIT implementation of the MachineCodeEmitter, which is
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/// used to output functions to memory for execution.
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class JITEmitter : public MachineCodeEmitter {
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JITMemoryManager MemMgr;
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// CurBlock - The start of the current block of memory. CurByte - The
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// current byte being emitted to.
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unsigned char *CurBlock, *CurByte;
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// When outputting a function stub in the context of some other function, we
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// save CurBlock and CurByte here.
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unsigned char *SavedCurBlock, *SavedCurByte;
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// ConstantPoolAddresses - Contains the location for each entry in the
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// constant pool.
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std::vector<void*> ConstantPoolAddresses;
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/// Relocations - These are the relocations that the function needs, as
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/// emitted.
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std::vector<MachineRelocation> Relocations;
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public:
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JITEmitter(JIT &jit) { TheJIT = &jit; }
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virtual void startFunction(MachineFunction &F);
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virtual void finishFunction(MachineFunction &F);
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virtual void emitConstantPool(MachineConstantPool *MCP);
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virtual void startFunctionStub(unsigned StubSize);
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virtual void* finishFunctionStub(const Function *F);
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virtual void emitByte(unsigned char B);
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virtual void emitWord(unsigned W);
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virtual void emitWordAt(unsigned W, unsigned *Ptr);
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virtual void addRelocation(const MachineRelocation &MR) {
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Relocations.push_back(MR);
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}
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virtual uint64_t getCurrentPCValue();
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virtual uint64_t getCurrentPCOffset();
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virtual uint64_t getConstantPoolEntryAddress(unsigned Entry);
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private:
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void *getPointerToGlobal(GlobalValue *GV, void *Reference, bool NoNeedStub);
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};
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}
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MachineCodeEmitter *JIT::createEmitter(JIT &jit) {
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return new JITEmitter(jit);
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}
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void *JITEmitter::getPointerToGlobal(GlobalValue *V, void *Reference,
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bool DoesntNeedStub) {
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if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
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/// FIXME: If we straightened things out, this could actually emit the
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/// global immediately instead of queuing it for codegen later!
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return TheJIT->getOrEmitGlobalVariable(GV);
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}
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// If we have already compiled the function, return a pointer to its body.
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Function *F = cast<Function>(V);
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void *ResultPtr = TheJIT->getPointerToGlobalIfAvailable(F);
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if (ResultPtr) return ResultPtr;
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if (F->hasExternalLinkage() && F->isExternal()) {
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// If this is an external function pointer, we can force the JIT to
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// 'compile' it, which really just adds it to the map.
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if (DoesntNeedStub)
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return TheJIT->getPointerToFunction(F);
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return getJITResolver(this).getFunctionStub(F);
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}
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// Okay, the function has not been compiled yet, if the target callback
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// mechanism is capable of rewriting the instruction directly, prefer to do
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// that instead of emitting a stub.
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if (DoesntNeedStub)
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return getJITResolver(this).AddCallbackAtLocation(F, Reference);
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// Otherwise, we have to emit a lazy resolving stub.
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return getJITResolver(this).getFunctionStub(F);
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}
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void JITEmitter::startFunction(MachineFunction &F) {
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CurByte = CurBlock = MemMgr.startFunctionBody();
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TheJIT->addGlobalMapping(F.getFunction(), CurBlock);
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}
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void JITEmitter::finishFunction(MachineFunction &F) {
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MemMgr.endFunctionBody(CurByte);
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ConstantPoolAddresses.clear();
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NumBytes += CurByte-CurBlock;
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if (!Relocations.empty()) {
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// Resolve the relocations to concrete pointers.
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for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
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MachineRelocation &MR = Relocations[i];
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void *ResultPtr;
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if (MR.isString())
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ResultPtr = TheJIT->getPointerToNamedFunction(MR.getString());
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else
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ResultPtr = getPointerToGlobal(MR.getGlobalValue(),
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CurBlock+MR.getMachineCodeOffset(),
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MR.doesntNeedFunctionStub());
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MR.setResultPointer(ResultPtr);
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}
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TheJIT->getJITInfo().relocate(CurBlock, &Relocations[0],
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Relocations.size());
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}
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DEBUG(std::cerr << "JIT: Finished CodeGen of [" << (void*)CurBlock
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<< "] Function: " << F.getFunction()->getName()
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<< ": " << CurByte-CurBlock << " bytes of text, "
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<< Relocations.size() << " relocations\n");
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Relocations.clear();
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}
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void JITEmitter::emitConstantPool(MachineConstantPool *MCP) {
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const std::vector<Constant*> &Constants = MCP->getConstants();
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if (Constants.empty()) return;
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for (unsigned i = 0, e = Constants.size(); i != e; ++i) {
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const Type *Ty = Constants[i]->getType();
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unsigned Size = (unsigned)TheJIT->getTargetData().getTypeSize(Ty);
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unsigned Alignment = TheJIT->getTargetData().getTypeAlignment(Ty);
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void *Addr = MemMgr.allocateConstant(Size, Alignment);
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TheJIT->InitializeMemory(Constants[i], Addr);
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ConstantPoolAddresses.push_back(Addr);
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}
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}
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void JITEmitter::startFunctionStub(unsigned StubSize) {
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SavedCurBlock = CurBlock; SavedCurByte = CurByte;
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CurByte = CurBlock = MemMgr.allocateStub(StubSize);
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}
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void *JITEmitter::finishFunctionStub(const Function *F) {
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NumBytes += CurByte-CurBlock;
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std::swap(CurBlock, SavedCurBlock);
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CurByte = SavedCurByte;
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return SavedCurBlock;
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}
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void JITEmitter::emitByte(unsigned char B) {
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*CurByte++ = B; // Write the byte to memory
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}
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void JITEmitter::emitWord(unsigned W) {
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// This won't work if the endianness of the host and target don't agree! (For
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// a JIT this can't happen though. :)
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*(unsigned*)CurByte = W;
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CurByte += sizeof(unsigned);
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}
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void JITEmitter::emitWordAt(unsigned W, unsigned *Ptr) {
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*Ptr = W;
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}
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// getConstantPoolEntryAddress - Return the address of the 'ConstantNum' entry
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// in the constant pool that was last emitted with the 'emitConstantPool'
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// method.
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//
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uint64_t JITEmitter::getConstantPoolEntryAddress(unsigned ConstantNum) {
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assert(ConstantNum < ConstantPoolAddresses.size() &&
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"Invalid ConstantPoolIndex!");
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return (intptr_t)ConstantPoolAddresses[ConstantNum];
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}
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// getCurrentPCValue - This returns the address that the next emitted byte
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// will be output to.
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//
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uint64_t JITEmitter::getCurrentPCValue() {
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return (intptr_t)CurByte;
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}
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uint64_t JITEmitter::getCurrentPCOffset() {
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return (intptr_t)CurByte-(intptr_t)CurBlock;
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}
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// getPointerToNamedFunction - This function is used as a global wrapper to
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// JIT::getPointerToNamedFunction for the purpose of resolving symbols when
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// bugpoint is debugging the JIT. In that scenario, we are loading an .so and
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// need to resolve function(s) that are being mis-codegenerated, so we need to
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// resolve their addresses at runtime, and this is the way to do it.
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extern "C" {
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void *getPointerToNamedFunction(const char *Name) {
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Module &M = TheJIT->getModule();
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if (Function *F = M.getNamedFunction(Name))
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return TheJIT->getPointerToFunction(F);
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return TheJIT->getPointerToNamedFunction(Name);
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}
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}
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