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//===-- X86JITInfo.cpp - Implement the JIT interfaces for the X86 target --===//
//
// 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 file implements the JIT interfaces for the X86 target.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "jit"
#include "X86JITInfo.h"
#include "X86Relocations.h"
#include "llvm/CodeGen/MachineCodeEmitter.h"
#include "llvm/Config/alloca.h"
#include <cstdlib>
#include <iostream>
using namespace llvm;
#ifdef _MSC_VER
extern "C" void *_AddressOfReturnAddress(void);
#pragma intrinsic(_AddressOfReturnAddress)
#endif
void X86JITInfo::replaceMachineCodeForFunction(void *Old, void *New) {
unsigned char *OldByte = (unsigned char *)Old;
*OldByte++ = 0xE9; // Emit JMP opcode.
unsigned *OldWord = (unsigned *)OldByte;
unsigned NewAddr = (intptr_t)New;
unsigned OldAddr = (intptr_t)OldWord;
*OldWord = NewAddr - OldAddr - 4; // Emit PC-relative addr of New code.
}
/// JITCompilerFunction - This contains the address of the JIT function used to
/// compile a function lazily.
static TargetJITInfo::JITCompilerFn JITCompilerFunction;
// Provide a wrapper for X86CompilationCallback2 that saves non-traditional
// callee saved registers, for the fastcc calling convention.
extern "C" {
#if defined(__i386__) || defined(i386) || defined(_M_IX86)
#ifndef _MSC_VER
void X86CompilationCallback(void);
asm(
".text\n"
".align 8\n"
#if defined(__CYGWIN__) || defined(__APPLE__) || defined(__MINGW32__)
".globl _X86CompilationCallback\n"
"_X86CompilationCallback:\n"
#else
".globl X86CompilationCallback\n"
"X86CompilationCallback:\n"
#endif
"pushl %ebp\n"
"movl %esp, %ebp\n" // Standard prologue
#if FASTCC_NUM_INT_ARGS_INREGS > 0
"pushl %eax\n"
"pushl %edx\n" // Save EAX/EDX
#endif
#if defined(__APPLE__)
"andl $-16, %esp\n" // Align ESP on 16-byte boundary
#endif
"subl $16, %esp\n"
"movl 4(%ebp), %eax\n" // Pass prev frame and return address
"movl %eax, 4(%esp)\n"
"movl %ebp, (%esp)\n"
#if defined(__CYGWIN__) || defined(__MINGW32__) || defined(__APPLE__)
"call _X86CompilationCallback2\n"
#else
"call X86CompilationCallback2\n"
#endif
#if defined(__APPLE__)
"movl %ebp, %esp\n" // Restore ESP
#endif
#if FASTCC_NUM_INT_ARGS_INREGS > 0
#if defined(__APPLE__)
"subl $8, %esp\n"
#endif
"popl %edx\n"
"popl %eax\n"
#endif
"popl %ebp\n"
"ret\n");
#else
void X86CompilationCallback2(void);
_declspec(naked) void X86CompilationCallback(void) {
__asm {
push eax
push edx
call X86CompilationCallback2
pop edx
pop eax
ret
}
}
#endif // _MSC_VER
#else // Not an i386 host
void X86CompilationCallback() {
std::cerr << "Cannot call X86CompilationCallback() on a non-x86 arch!\n";
abort();
}
#endif
}
/// X86CompilationCallback - This is the target-specific function invoked by the
/// function stub when we did not know the real target of a call. This function
/// must locate the start of the stub or call site and pass it into the JIT
/// compiler function.
#ifdef _MSC_VER
extern "C" void X86CompilationCallback2() {
assert(sizeof(size_t) == 4); // FIXME: handle Win64
unsigned *RetAddrLoc = (unsigned *)_AddressOfReturnAddress();
RetAddrLoc += 3; // skip over ret addr, edx, eax
unsigned RetAddr = *RetAddrLoc;
#else
extern "C" void X86CompilationCallback2(intptr_t *StackPtr, intptr_t RetAddr) {
intptr_t *RetAddrLoc = &StackPtr[1];
#endif
assert(*RetAddrLoc == RetAddr &&
"Could not find return address on the stack!");
// It's a stub if there is an interrupt marker after the call.
bool isStub = ((unsigned char*)(intptr_t)RetAddr)[0] == 0xCD;
// The call instruction should have pushed the return value onto the stack...
RetAddr -= 4; // Backtrack to the reference itself...
#if 0
DEBUG(std::cerr << "In callback! Addr=" << (void*)RetAddr
<< " ESP=" << (void*)StackPtr
<< ": Resolving call to function: "
<< TheVM->getFunctionReferencedName((void*)RetAddr) << "\n");
#endif
// Sanity check to make sure this really is a call instruction.
assert(((unsigned char*)(intptr_t)RetAddr)[-1] == 0xE8 &&"Not a call instr!");
unsigned NewVal = (intptr_t)JITCompilerFunction((void*)(intptr_t)RetAddr);
// Rewrite the call target... so that we don't end up here every time we
// execute the call.
*(unsigned*)(intptr_t)RetAddr = NewVal-RetAddr-4;
if (isStub) {
// If this is a stub, rewrite the call into an unconditional branch
// instruction so that two return addresses are not pushed onto the stack
// when the requested function finally gets called. This also makes the
// 0xCD byte (interrupt) dead, so the marker doesn't effect anything.
((unsigned char*)(intptr_t)RetAddr)[-1] = 0xE9;
}
// Change the return address to reexecute the call instruction...
*RetAddrLoc -= 5;
}
TargetJITInfo::LazyResolverFn
X86JITInfo::getLazyResolverFunction(JITCompilerFn F) {
JITCompilerFunction = F;
return X86CompilationCallback;
}
void *X86JITInfo::emitFunctionStub(void *Fn, MachineCodeEmitter &MCE) {
// Note, we cast to intptr_t here to silence a -pedantic warning that
// complains about casting a function pointer to a normal pointer.
if (Fn != (void*)(intptr_t)X86CompilationCallback) {
MCE.startFunctionStub(5);
MCE.emitByte(0xE9);
MCE.emitWordLE((intptr_t)Fn-MCE.getCurrentPCValue()-4);
return MCE.finishFunctionStub(0);
}
MCE.startFunctionStub(6);
MCE.emitByte(0xE8); // Call with 32 bit pc-rel destination...
MCE.emitWordLE((intptr_t)Fn-MCE.getCurrentPCValue()-4);
MCE.emitByte(0xCD); // Interrupt - Just a marker identifying the stub!
return MCE.finishFunctionStub(0);
}
/// relocate - Before the JIT can run a block of code that has been emitted,
/// it must rewrite the code to contain the actual addresses of any
/// referenced global symbols.
void X86JITInfo::relocate(void *Function, MachineRelocation *MR,
unsigned NumRelocs, unsigned char* GOTBase) {
for (unsigned i = 0; i != NumRelocs; ++i, ++MR) {
void *RelocPos = (char*)Function + MR->getMachineCodeOffset();
intptr_t ResultPtr = (intptr_t)MR->getResultPointer();
switch ((X86::RelocationType)MR->getRelocationType()) {
case X86::reloc_pcrel_word:
// PC relative relocation, add the relocated value to the value already in
// memory, after we adjust it for where the PC is.
ResultPtr = ResultPtr-(intptr_t)RelocPos-4;
*((intptr_t*)RelocPos) += ResultPtr;
break;
case X86::reloc_absolute_word:
// Absolute relocation, just add the relocated value to the value already
// in memory.
*((intptr_t*)RelocPos) += ResultPtr;
break;
}
}
}
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