lib/Target/X86/X86JITInfo.cpp

   1 //===-- X86JITInfo.cpp - Implement the JIT interfaces for the X86 target --===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the JIT interfaces for the X86 target.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #define DEBUG_TYPE "jit"
  15 #include "X86JITInfo.h"
  16 #include "X86Relocations.h"
  17 #include "X86Subtarget.h"
  18 #include "X86TargetMachine.h"
  19 #include "llvm/Function.h"
  20 #include "llvm/Support/Compiler.h"
  21 #include "llvm/Support/ErrorHandling.h"
  22 #include "llvm/Support/Valgrind.h"
  23 #include <cstdlib>
  24 #include <cstring>
  25 using namespace llvm;
  26
  27 // Determine the platform we're running on
  28 #if defined (__x86_64__) || defined (_M_AMD64) || defined (_M_X64)
  29 # define X86_64_JIT
  30 #elif defined(__i386__) || defined(i386) || defined(_M_IX86)
  31 # define X86_32_JIT
  32 #endif
  33
  34 void X86JITInfo::replaceMachineCodeForFunction(void *Old, void *New) {
  35   unsigned char *OldByte = (unsigned char *)Old;
  36   *OldByte++ = 0xE9;                // Emit JMP opcode.
  37   unsigned *OldWord = (unsigned *)OldByte;
  38   unsigned NewAddr = (intptr_t)New;
  39   unsigned OldAddr = (intptr_t)OldWord;
  40   *OldWord = NewAddr - OldAddr - 4; // Emit PC-relative addr of New code.
  41
  42   // X86 doesn't need to invalidate the processor cache, so just invalidate
  43   // Valgrind's cache directly.
  44   sys::ValgrindDiscardTranslations(Old, 5);
  45 }
  46
  47
  48 /// JITCompilerFunction - This contains the address of the JIT function used to
  49 /// compile a function lazily.
  50 static TargetJITInfo::JITCompilerFn JITCompilerFunction;
  51
  52 // Get the ASMPREFIX for the current host.  This is often '_'.
  53 #ifndef __USER_LABEL_PREFIX__
  54 #define __USER_LABEL_PREFIX__
  55 #endif
  56 #define GETASMPREFIX2(X) #X
  57 #define GETASMPREFIX(X) GETASMPREFIX2(X)
  58 #define ASMPREFIX GETASMPREFIX(__USER_LABEL_PREFIX__)
  59
  60 // For ELF targets, use a .size and .type directive, to let tools
  61 // know the extent of functions defined in assembler.
  62 #if defined(__ELF__)
  63 # define SIZE(sym) ".size " #sym ", . - " #sym "\n"
  64 # define TYPE_FUNCTION(sym) ".type " #sym ", @function\n"
  65 #else
  66 # define SIZE(sym)
  67 # define TYPE_FUNCTION(sym)
  68 #endif
  69
  70 // Provide a convenient way for disabling usage of CFI directives.
  71 // This is needed for old/broken assemblers (for example, gas on
  72 // Darwin is pretty old and doesn't support these directives)
  73 #if defined(__APPLE__)
  74 # define CFI(x)
  75 #else
  76 // FIXME: Disable this until we really want to use it. Also, we will
  77 //        need to add some workarounds for compilers, which support
  78 //        only subset of these directives.
  79 # define CFI(x)
  80 #endif
  81
  82 // Provide a wrapper for X86CompilationCallback2 that saves non-traditional
  83 // callee saved registers, for the fastcc calling convention.
  84 extern "C" {
  85 #if defined(X86_64_JIT)
  86 # ifndef _MSC_VER
  87   // No need to save EAX/EDX for X86-64.
  88   void X86CompilationCallback(void);
  89   asm(
  90     ".text\n"
  91     ".align 8\n"
  92     ".globl " ASMPREFIX "X86CompilationCallback\n"
  93     TYPE_FUNCTION(X86CompilationCallback)
  94   ASMPREFIX "X86CompilationCallback:\n"
  95     CFI(".cfi_startproc\n")
  96     // Save RBP
  97     "pushq   %rbp\n"
  98     CFI(".cfi_def_cfa_offset 16\n")
  99     CFI(".cfi_offset %rbp, -16\n")
 100     // Save RSP
 101     "movq    %rsp, %rbp\n"
 102     CFI(".cfi_def_cfa_register %rbp\n")
 103     // Save all int arg registers
 104     "pushq   %rdi\n"
 105     CFI(".cfi_rel_offset %rdi, 0\n")
 106     "pushq   %rsi\n"
 107     CFI(".cfi_rel_offset %rsi, 8\n")
 108     "pushq   %rdx\n"
 109     CFI(".cfi_rel_offset %rdx, 16\n")
 110     "pushq   %rcx\n"
 111     CFI(".cfi_rel_offset %rcx, 24\n")
 112     "pushq   %r8\n"
 113     CFI(".cfi_rel_offset %r8, 32\n")
 114     "pushq   %r9\n"
 115     CFI(".cfi_rel_offset %r9, 40\n")
 116     // Align stack on 16-byte boundary. ESP might not be properly aligned
 117     // (8 byte) if this is called from an indirect stub.
 118     "andq    $-16, %rsp\n"
 119     // Save all XMM arg registers
 120     "subq    $128, %rsp\n"
 121     "movaps  %xmm0, (%rsp)\n"
 122     "movaps  %xmm1, 16(%rsp)\n"
 123     "movaps  %xmm2, 32(%rsp)\n"
 124     "movaps  %xmm3, 48(%rsp)\n"
 125     "movaps  %xmm4, 64(%rsp)\n"
 126     "movaps  %xmm5, 80(%rsp)\n"
 127     "movaps  %xmm6, 96(%rsp)\n"
 128     "movaps  %xmm7, 112(%rsp)\n"
 129     // JIT callee
 130 #ifdef _WIN64
 131     "subq    $32, %rsp\n"
 132     "movq    %rbp, %rcx\n"    // Pass prev frame and return address
 133     "movq    8(%rbp), %rdx\n"
 134     "call    " ASMPREFIX "X86CompilationCallback2\n"
 135     "addq    $32, %rsp\n"
 136 #else
 137     "movq    %rbp, %rdi\n"    // Pass prev frame and return address
 138     "movq    8(%rbp), %rsi\n"
 139     "call    " ASMPREFIX "X86CompilationCallback2\n"
 140 #endif
 141     // Restore all XMM arg registers
 142     "movaps  112(%rsp), %xmm7\n"
 143     "movaps  96(%rsp), %xmm6\n"
 144     "movaps  80(%rsp), %xmm5\n"
 145     "movaps  64(%rsp), %xmm4\n"
 146     "movaps  48(%rsp), %xmm3\n"
 147     "movaps  32(%rsp), %xmm2\n"
 148     "movaps  16(%rsp), %xmm1\n"
 149     "movaps  (%rsp), %xmm0\n"
 150     // Restore RSP
 151     "movq    %rbp, %rsp\n"
 152     CFI(".cfi_def_cfa_register %rsp\n")
 153     // Restore all int arg registers
 154     "subq    $48, %rsp\n"
 155     CFI(".cfi_adjust_cfa_offset 48\n")
 156     "popq    %r9\n"
 157     CFI(".cfi_adjust_cfa_offset -8\n")
 158     CFI(".cfi_restore %r9\n")
 159     "popq    %r8\n"
 160     CFI(".cfi_adjust_cfa_offset -8\n")
 161     CFI(".cfi_restore %r8\n")
 162     "popq    %rcx\n"
 163     CFI(".cfi_adjust_cfa_offset -8\n")
 164     CFI(".cfi_restore %rcx\n")
 165     "popq    %rdx\n"
 166     CFI(".cfi_adjust_cfa_offset -8\n")
 167     CFI(".cfi_restore %rdx\n")
 168     "popq    %rsi\n"
 169     CFI(".cfi_adjust_cfa_offset -8\n")
 170     CFI(".cfi_restore %rsi\n")
 171     "popq    %rdi\n"
 172     CFI(".cfi_adjust_cfa_offset -8\n")
 173     CFI(".cfi_restore %rdi\n")
 174     // Restore RBP
 175     "popq    %rbp\n"
 176     CFI(".cfi_adjust_cfa_offset -8\n")
 177     CFI(".cfi_restore %rbp\n")
 178     "ret\n"
 179     CFI(".cfi_endproc\n")
 180     SIZE(X86CompilationCallback)
 181   );
 182 # else
 183   // No inline assembler support on this platform. The routine is in external
 184   // file.
 185   void X86CompilationCallback();
 186
 187 # endif
 188 #elif defined (X86_32_JIT)
 189 # ifndef _MSC_VER
 190   void X86CompilationCallback(void);
 191   asm(
 192     ".text\n"
 193     ".align 8\n"
 194     ".globl " ASMPREFIX "X86CompilationCallback\n"
 195     TYPE_FUNCTION(X86CompilationCallback)
 196   ASMPREFIX "X86CompilationCallback:\n"
 197     CFI(".cfi_startproc\n")
 198     "pushl   %ebp\n"
 199     CFI(".cfi_def_cfa_offset 8\n")
 200     CFI(".cfi_offset %ebp, -8\n")
 201     "movl    %esp, %ebp\n"    // Standard prologue
 202     CFI(".cfi_def_cfa_register %ebp\n")
 203     "pushl   %eax\n"
 204     CFI(".cfi_rel_offset %eax, 0\n")
 205     "pushl   %edx\n"          // Save EAX/EDX/ECX
 206     CFI(".cfi_rel_offset %edx, 4\n")
 207     "pushl   %ecx\n"
 208     CFI(".cfi_rel_offset %ecx, 8\n")
 209 #  if defined(__APPLE__)
 210     "andl    $-16, %esp\n"    // Align ESP on 16-byte boundary
 211 #  endif
 212     "subl    $16, %esp\n"
 213     "movl    4(%ebp), %eax\n" // Pass prev frame and return address
 214     "movl    %eax, 4(%esp)\n"
 215     "movl    %ebp, (%esp)\n"
 216     "call    " ASMPREFIX "X86CompilationCallback2\n"
 217     "movl    %ebp, %esp\n"    // Restore ESP
 218     CFI(".cfi_def_cfa_register %esp\n")
 219     "subl    $12, %esp\n"
 220     CFI(".cfi_adjust_cfa_offset 12\n")
 221     "popl    %ecx\n"
 222     CFI(".cfi_adjust_cfa_offset -4\n")
 223     CFI(".cfi_restore %ecx\n")
 224     "popl    %edx\n"
 225     CFI(".cfi_adjust_cfa_offset -4\n")
 226     CFI(".cfi_restore %edx\n")
 227     "popl    %eax\n"
 228     CFI(".cfi_adjust_cfa_offset -4\n")
 229     CFI(".cfi_restore %eax\n")
 230     "popl    %ebp\n"
 231     CFI(".cfi_adjust_cfa_offset -4\n")
 232     CFI(".cfi_restore %ebp\n")
 233     "ret\n"
 234     CFI(".cfi_endproc\n")
 235     SIZE(X86CompilationCallback)
 236   );
 237
 238   // Same as X86CompilationCallback but also saves XMM argument registers.
 239   void X86CompilationCallback_SSE(void);
 240   asm(
 241     ".text\n"
 242     ".align 8\n"
 243     ".globl " ASMPREFIX "X86CompilationCallback_SSE\n"
 244     TYPE_FUNCTION(X86CompilationCallback_SSE)
 245   ASMPREFIX "X86CompilationCallback_SSE:\n"
 246     CFI(".cfi_startproc\n")
 247     "pushl   %ebp\n"
 248     CFI(".cfi_def_cfa_offset 8\n")
 249     CFI(".cfi_offset %ebp, -8\n")
 250     "movl    %esp, %ebp\n"    // Standard prologue
 251     CFI(".cfi_def_cfa_register %ebp\n")
 252     "pushl   %eax\n"
 253     CFI(".cfi_rel_offset %eax, 0\n")
 254     "pushl   %edx\n"          // Save EAX/EDX/ECX
 255     CFI(".cfi_rel_offset %edx, 4\n")
 256     "pushl   %ecx\n"
 257     CFI(".cfi_rel_offset %ecx, 8\n")
 258     "andl    $-16, %esp\n"    // Align ESP on 16-byte boundary
 259     // Save all XMM arg registers
 260     "subl    $64, %esp\n"
 261     // FIXME: provide frame move information for xmm registers.
 262     // This can be tricky, because CFA register is ebp (unaligned)
 263     // and we need to produce offsets relative to it.
 264     "movaps  %xmm0, (%esp)\n"
 265     "movaps  %xmm1, 16(%esp)\n"
 266     "movaps  %xmm2, 32(%esp)\n"
 267     "movaps  %xmm3, 48(%esp)\n"
 268     "subl    $16, %esp\n"
 269     "movl    4(%ebp), %eax\n" // Pass prev frame and return address
 270     "movl    %eax, 4(%esp)\n"
 271     "movl    %ebp, (%esp)\n"
 272     "call    " ASMPREFIX "X86CompilationCallback2\n"
 273     "addl    $16, %esp\n"
 274     "movaps  48(%esp), %xmm3\n"
 275     CFI(".cfi_restore %xmm3\n")
 276     "movaps  32(%esp), %xmm2\n"
 277     CFI(".cfi_restore %xmm2\n")
 278     "movaps  16(%esp), %xmm1\n"
 279     CFI(".cfi_restore %xmm1\n")
 280     "movaps  (%esp), %xmm0\n"
 281     CFI(".cfi_restore %xmm0\n")
 282     "movl    %ebp, %esp\n"    // Restore ESP
 283     CFI(".cfi_def_cfa_register esp\n")
 284     "subl    $12, %esp\n"
 285     CFI(".cfi_adjust_cfa_offset 12\n")
 286     "popl    %ecx\n"
 287     CFI(".cfi_adjust_cfa_offset -4\n")
 288     CFI(".cfi_restore %ecx\n")
 289     "popl    %edx\n"
 290     CFI(".cfi_adjust_cfa_offset -4\n")
 291     CFI(".cfi_restore %edx\n")
 292     "popl    %eax\n"
 293     CFI(".cfi_adjust_cfa_offset -4\n")
 294     CFI(".cfi_restore %eax\n")
 295     "popl    %ebp\n"
 296     CFI(".cfi_adjust_cfa_offset -4\n")
 297     CFI(".cfi_restore %ebp\n")
 298     "ret\n"
 299     CFI(".cfi_endproc\n")
 300     SIZE(X86CompilationCallback_SSE)
 301   );
 302 # else
 303   void X86CompilationCallback2(intptr_t *StackPtr, intptr_t RetAddr);
 304
 305   _declspec(naked) void X86CompilationCallback(void) {
 306     __asm {
 307       push  ebp
 308       mov   ebp, esp
 309       push  eax
 310       push  edx
 311       push  ecx
 312       and   esp, -16
 313       sub   esp, 16
 314       mov   eax, dword ptr [ebp+4]
 315       mov   dword ptr [esp+4], eax
 316       mov   dword ptr [esp], ebp
 317       call  X86CompilationCallback2
 318       mov   esp, ebp
 319       sub   esp, 12
 320       pop   ecx
 321       pop   edx
 322       pop   eax
 323       pop   ebp
 324       ret
 325     }
 326   }
 327
 328 # endif // _MSC_VER
 329
 330 #else // Not an i386 host
 331   void X86CompilationCallback() {
 332     llvm_unreachable("Cannot call X86CompilationCallback() on a non-x86 arch!");
 333   }
 334 #endif
 335 }
 336
 337 /// X86CompilationCallback2 - This is the target-specific function invoked by the
 338 /// function stub when we did not know the real target of a call.  This function
 339 /// must locate the start of the stub or call site and pass it into the JIT
 340 /// compiler function.
 341 extern "C" {
 342 #if !(defined (X86_64_JIT) && defined(_MSC_VER))
 343  // the following function is called only from this translation unit,
 344  // unless we are under 64bit Windows with MSC, where there is
 345  // no support for inline assembly
 346 static
 347 #endif
 348 void LLVM_ATTRIBUTE_USED
 349 X86CompilationCallback2(intptr_t *StackPtr, intptr_t RetAddr) {
 350   intptr_t *RetAddrLoc = &StackPtr[1];
 351   assert(*RetAddrLoc == RetAddr &&
 352          "Could not find return address on the stack!");
 353
 354   // It's a stub if there is an interrupt marker after the call.
 355   bool isStub = ((unsigned char*)RetAddr)[0] == 0xCE;
 356
 357   // The call instruction should have pushed the return value onto the stack...
 358 #if defined (X86_64_JIT)
 359   RetAddr--;     // Backtrack to the reference itself...
 360 #else
 361   RetAddr -= 4;  // Backtrack to the reference itself...
 362 #endif
 363
 364 #if 0
 365   DEBUG(dbgs() << "In callback! Addr=" << (void*)RetAddr
 366                << " ESP=" << (void*)StackPtr
 367                << ": Resolving call to function: "
 368                << TheVM->getFunctionReferencedName((void*)RetAddr) << "\n");
 369 #endif
 370
 371   // Sanity check to make sure this really is a call instruction.
 372 #if defined (X86_64_JIT)
 373   assert(((unsigned char*)RetAddr)[-2] == 0x41 &&"Not a call instr!");
 374   assert(((unsigned char*)RetAddr)[-1] == 0xFF &&"Not a call instr!");
 375 #else
 376   assert(((unsigned char*)RetAddr)[-1] == 0xE8 &&"Not a call instr!");
 377 #endif
 378
 379   intptr_t NewVal = (intptr_t)JITCompilerFunction((void*)RetAddr);
 380
 381   // Rewrite the call target... so that we don't end up here every time we
 382   // execute the call.
 383 #if defined (X86_64_JIT)
 384   assert(isStub &&
 385          "X86-64 doesn't support rewriting non-stub lazy compilation calls:"
 386          " the call instruction varies too much.");
 387 #else
 388   *(intptr_t *)RetAddr = (intptr_t)(NewVal-RetAddr-4);
 389 #endif
 390
 391   if (isStub) {
 392     // If this is a stub, rewrite the call into an unconditional branch
 393     // instruction so that two return addresses are not pushed onto the stack
 394     // when the requested function finally gets called.  This also makes the
 395     // 0xCE byte (interrupt) dead, so the marker doesn't effect anything.
 396 #if defined (X86_64_JIT)
 397     // If the target address is within 32-bit range of the stub, use a
 398     // PC-relative branch instead of loading the actual address.  (This is
 399     // considerably shorter than the 64-bit immediate load already there.)
 400     // We assume here intptr_t is 64 bits.
 401     intptr_t diff = NewVal-RetAddr+7;
 402     if (diff >= -2147483648LL && diff <= 2147483647LL) {
 403       *(unsigned char*)(RetAddr-0xc) = 0xE9;
 404       *(intptr_t *)(RetAddr-0xb) = diff & 0xffffffff;
 405     } else {
 406       *(intptr_t *)(RetAddr - 0xa) = NewVal;
 407       ((unsigned char*)RetAddr)[0] = (2 | (4 << 3) | (3 << 6));
 408     }
 409     sys::ValgrindDiscardTranslations((void*)(RetAddr-0xc), 0xd);
 410 #else
 411     ((unsigned char*)RetAddr)[-1] = 0xE9;
 412     sys::ValgrindDiscardTranslations((void*)(RetAddr-1), 5);
 413 #endif
 414   }
 415
 416   // Change the return address to reexecute the call instruction...
 417 #if defined (X86_64_JIT)
 418   *RetAddrLoc -= 0xd;
 419 #else
 420   *RetAddrLoc -= 5;
 421 #endif
 422 }
 423 }
 424
 425 TargetJITInfo::LazyResolverFn
 426 X86JITInfo::getLazyResolverFunction(JITCompilerFn F) {
 427   JITCompilerFunction = F;
 428
 429 #if defined (X86_32_JIT) && !defined (_MSC_VER)
 430   if (Subtarget->hasSSE1())
 431     return X86CompilationCallback_SSE;
 432 #endif
 433
 434   return X86CompilationCallback;
 435 }
 436
 437 X86JITInfo::X86JITInfo(X86TargetMachine &tm) : TM(tm) {
 438   Subtarget = &TM.getSubtarget<X86Subtarget>();
 439   useGOT = 0;
 440   TLSOffset = 0;
 441 }
 442
 443 void *X86JITInfo::emitGlobalValueIndirectSym(const GlobalValue* GV, void *ptr,
 444                                              JITCodeEmitter &JCE) {
 445 #if defined (X86_64_JIT)
 446   const unsigned Alignment = 8;
 447   uint8_t Buffer[8];
 448   uint8_t *Cur = Buffer;
 449   MachineCodeEmitter::emitWordLEInto(Cur, (unsigned)(intptr_t)ptr);
 450   MachineCodeEmitter::emitWordLEInto(Cur, (unsigned)(((intptr_t)ptr) >> 32));
 451 #else
 452   const unsigned Alignment = 4;
 453   uint8_t Buffer[4];
 454   uint8_t *Cur = Buffer;
 455   MachineCodeEmitter::emitWordLEInto(Cur, (intptr_t)ptr);
 456 #endif
 457   return JCE.allocIndirectGV(GV, Buffer, sizeof(Buffer), Alignment);
 458 }
 459
 460 TargetJITInfo::StubLayout X86JITInfo::getStubLayout() {
 461   // The 64-bit stub contains:
 462   //   movabs r10 <- 8-byte-target-address  # 10 bytes
 463   //   call|jmp *r10  # 3 bytes
 464   // The 32-bit stub contains a 5-byte call|jmp.
 465   // If the stub is a call to the compilation callback, an extra byte is added
 466   // to mark it as a stub.
 467   StubLayout Result = {14, 4};
 468   return Result;
 469 }
 470
 471 void *X86JITInfo::emitFunctionStub(const Function* F, void *Target,
 472                                    JITCodeEmitter &JCE) {
 473   // Note, we cast to intptr_t here to silence a -pedantic warning that
 474   // complains about casting a function pointer to a normal pointer.
 475 #if defined (X86_32_JIT) && !defined (_MSC_VER)
 476   bool NotCC = (Target != (void*)(intptr_t)X86CompilationCallback &&
 477                 Target != (void*)(intptr_t)X86CompilationCallback_SSE);
 478 #else
 479   bool NotCC = Target != (void*)(intptr_t)X86CompilationCallback;
 480 #endif
 481   JCE.emitAlignment(4);
 482   void *Result = (void*)JCE.getCurrentPCValue();
 483   if (NotCC) {
 484 #if defined (X86_64_JIT)
 485     JCE.emitByte(0x49);          // REX prefix
 486     JCE.emitByte(0xB8+2);        // movabsq r10
 487     JCE.emitWordLE((unsigned)(intptr_t)Target);
 488     JCE.emitWordLE((unsigned)(((intptr_t)Target) >> 32));
 489     JCE.emitByte(0x41);          // REX prefix
 490     JCE.emitByte(0xFF);          // jmpq *r10
 491     JCE.emitByte(2 | (4 << 3) | (3 << 6));
 492 #else
 493     JCE.emitByte(0xE9);
 494     JCE.emitWordLE((intptr_t)Target-JCE.getCurrentPCValue()-4);
 495 #endif
 496     return Result;
 497   }
 498
 499 #if defined (X86_64_JIT)
 500   JCE.emitByte(0x49);          // REX prefix
 501   JCE.emitByte(0xB8+2);        // movabsq r10
 502   JCE.emitWordLE((unsigned)(intptr_t)Target);
 503   JCE.emitWordLE((unsigned)(((intptr_t)Target) >> 32));
 504   JCE.emitByte(0x41);          // REX prefix
 505   JCE.emitByte(0xFF);          // callq *r10
 506   JCE.emitByte(2 | (2 << 3) | (3 << 6));
 507 #else
 508   JCE.emitByte(0xE8);   // Call with 32 bit pc-rel destination...
 509
 510   JCE.emitWordLE((intptr_t)Target-JCE.getCurrentPCValue()-4);
 511 #endif
 512
 513   // This used to use 0xCD, but that value is used by JITMemoryManager to
 514   // initialize the buffer with garbage, which means it may follow a
 515   // noreturn function call, confusing X86CompilationCallback2.  PR 4929.
 516   JCE.emitByte(0xCE);   // Interrupt - Just a marker identifying the stub!
 517   return Result;
 518 }
 519
 520 /// getPICJumpTableEntry - Returns the value of the jumptable entry for the
 521 /// specific basic block.
 522 uintptr_t X86JITInfo::getPICJumpTableEntry(uintptr_t BB, uintptr_t Entry) {
 523 #if defined(X86_64_JIT)
 524   return BB - Entry;
 525 #else
 526   return BB - PICBase;
 527 #endif
 528 }
 529
 530 /// relocate - Before the JIT can run a block of code that has been emitted,
 531 /// it must rewrite the code to contain the actual addresses of any
 532 /// referenced global symbols.
 533 void X86JITInfo::relocate(void *Function, MachineRelocation *MR,
 534                           unsigned NumRelocs, unsigned char* GOTBase) {
 535   for (unsigned i = 0; i != NumRelocs; ++i, ++MR) {
 536     void *RelocPos = (char*)Function + MR->getMachineCodeOffset();
 537     intptr_t ResultPtr = (intptr_t)MR->getResultPointer();
 538     switch ((X86::RelocationType)MR->getRelocationType()) {
 539     case X86::reloc_pcrel_word: {
 540       // PC relative relocation, add the relocated value to the value already in
 541       // memory, after we adjust it for where the PC is.
 542       ResultPtr = ResultPtr -(intptr_t)RelocPos - 4 - MR->getConstantVal();
 543       *((unsigned*)RelocPos) += (unsigned)ResultPtr;
 544       break;
 545     }
 546     case X86::reloc_picrel_word: {
 547       // PIC base relative relocation, add the relocated value to the value
 548       // already in memory, after we adjust it for where the PIC base is.
 549       ResultPtr = ResultPtr - ((intptr_t)Function + MR->getConstantVal());
 550       *((unsigned*)RelocPos) += (unsigned)ResultPtr;
 551       break;
 552     }
 553     case X86::reloc_absolute_word:
 554     case X86::reloc_absolute_word_sext:
 555       // Absolute relocation, just add the relocated value to the value already
 556       // in memory.
 557       *((unsigned*)RelocPos) += (unsigned)ResultPtr;
 558       break;
 559     case X86::reloc_absolute_dword:
 560       *((intptr_t*)RelocPos) += ResultPtr;
 561       break;
 562     }
 563   }
 564 }
 565
 566 char* X86JITInfo::allocateThreadLocalMemory(size_t size) {
 567 #if defined(X86_32_JIT) && !defined(__APPLE__) && !defined(_MSC_VER)
 568   TLSOffset -= size;
 569   return TLSOffset;
 570 #else
 571   llvm_unreachable("Cannot allocate thread local storage on this arch!");
 572   return 0;
 573 #endif
 574 }