--- /dev/null
+//===-- 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"
+using namespace llvm;
+
+void *X86JITInfo::emitFunctionStub(void *Fn, MachineCodeEmitter &MCE) {
+ MCE.startFunctionStub(6);
+ MCE.emitByte(0xE8); // Call with 32 bit pc-rel destination...
+
+ MCE.emitWord((intptr_t)Fn-MCE.getCurrentPCValue()-4);
+
+ MCE.emitByte(0xCD); // Interrupt - Just a marker identifying the stub!
+ return MCE.finishFunctionStub(0);
+}
+
+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.
+}
+
+
+#ifdef _MSC_VER
+#pragma optimize("y", off)
+#endif
+
+/// JITCompilerFunction - This contains the address of the JIT function used to
+/// compile a function lazily.
+static TargetJITInfo::JITCompilerFn JITCompilerFunction;
+
+/// CompilationCallback - 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.
+static void CompilationCallback() {
+#ifdef _MSC_VER
+ unsigned *StackPtr, RetAddr;
+ __asm mov StackPtr, ebp;
+ __asm mov eax, DWORD PTR [ebp + 4];
+ __asm mov RetAddr, eax;
+#else
+ unsigned *StackPtr = (unsigned*)__builtin_frame_address(0);
+ unsigned RetAddr = (unsigned)(intptr_t)__builtin_return_address(0);
+
+ // NOTE: __builtin_frame_address doesn't work if frame pointer elimination has
+ // been performed. Having a variable sized alloca disables frame pointer
+ // elimination currently, even if it's dead. This is a gross hack.
+ alloca(10+(RetAddr >> 31));
+
+#endif
+ assert(StackPtr[1] == 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...
+ StackPtr[1] -= 5;
+}
+
+#ifdef _MSC_VER
+#pragma optimize( "", on )
+#endif
+
+TargetJITInfo::LazyResolverFn
+X86JITInfo::getLazyResolverFunction(JITCompilerFn F) {
+ JITCompilerFunction = F;
+ return CompilationCallback;
+}
+
+
+/// 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) {
+ 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;
+ }
+ }
+}
+