[llvm-commits] CVS: llvm/lib/Target/X86/X86JITInfo.cpp

[Chris Lattner]

Changes in directory llvm/lib/Target/X86:

X86JITInfo.cpp added (r1.1)
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Log message:

Implement the X86 JIT interfaces


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Diffs of the changes:  (+140 -0)

Index: llvm/lib/Target/X86/X86JITInfo.cpp
diff -c /dev/null llvm/lib/Target/X86/X86JITInfo.cpp:1.1
*** /dev/null	Sat Nov 20 17:54:43 2004
--- llvm/lib/Target/X86/X86JITInfo.cpp	Sat Nov 20 17:54:33 2004
***************
*** 0 ****
--- 1,140 ----
+ //===-- 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;
+     }
+   }
+ }
+