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cpython/Python/jit.c

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#ifdef _Py_JIT
#include "Python.h"
#include "pycore_abstract.h"
#include "pycore_call.h"
#include "pycore_ceval.h"
#include "pycore_dict.h"
#include "pycore_intrinsics.h"
#include "pycore_long.h"
#include "pycore_opcode_metadata.h"
#include "pycore_opcode_utils.h"
#include "pycore_optimizer.h"
#include "pycore_pyerrors.h"
#include "pycore_setobject.h"
#include "pycore_sliceobject.h"
#include "pycore_jit.h"
#include "jit_stencils.h"
// Memory management stuff: ////////////////////////////////////////////////////
#ifndef MS_WINDOWS
#include <sys/mman.h>
#endif
static size_t
get_page_size(void)
{
#ifdef MS_WINDOWS
SYSTEM_INFO si;
GetSystemInfo(&si);
return si.dwPageSize;
#else
return sysconf(_SC_PAGESIZE);
#endif
}
static void
jit_error(const char *message)
{
#ifdef MS_WINDOWS
int hint = GetLastError();
#else
int hint = errno;
#endif
PyErr_Format(PyExc_RuntimeWarning, "JIT %s (%d)", message, hint);
}
static unsigned char *
jit_alloc(size_t size)
{
assert(size);
assert(size % get_page_size() == 0);
#ifdef MS_WINDOWS
int flags = MEM_COMMIT | MEM_RESERVE;
unsigned char *memory = VirtualAlloc(NULL, size, flags, PAGE_READWRITE);
int failed = memory == NULL;
#else
int flags = MAP_ANONYMOUS | MAP_PRIVATE;
unsigned char *memory = mmap(NULL, size, PROT_READ | PROT_WRITE, flags, -1, 0);
int failed = memory == MAP_FAILED;
#endif
if (failed) {
jit_error("unable to allocate memory");
return NULL;
}
return memory;
}
static int
jit_free(unsigned char *memory, size_t size)
{
assert(size);
assert(size % get_page_size() == 0);
#ifdef MS_WINDOWS
int failed = !VirtualFree(memory, 0, MEM_RELEASE);
#else
int failed = munmap(memory, size);
#endif
if (failed) {
jit_error("unable to free memory");
return -1;
}
return 0;
}
static int
mark_executable(unsigned char *memory, size_t size)
{
if (size == 0) {
return 0;
}
assert(size % get_page_size() == 0);
// Do NOT ever leave the memory writable! Also, don't forget to flush the
// i-cache (I cannot begin to tell you how horrible that is to debug):
#ifdef MS_WINDOWS
if (!FlushInstructionCache(GetCurrentProcess(), memory, size)) {
jit_error("unable to flush instruction cache");
return -1;
}
int old;
int failed = !VirtualProtect(memory, size, PAGE_EXECUTE_READ, &old);
#else
__builtin___clear_cache((char *)memory, (char *)memory + size);
int failed = mprotect(memory, size, PROT_EXEC | PROT_READ);
#endif
if (failed) {
jit_error("unable to protect executable memory");
return -1;
}
return 0;
}
// JIT compiler stuff: /////////////////////////////////////////////////////////
// Warning! AArch64 requires you to get your hands dirty. These are your gloves:
// value[value_start : value_start + len]
static uint32_t
get_bits(uint64_t value, uint8_t value_start, uint8_t width)
{
assert(width <= 32);
return (value >> value_start) & ((1ULL << width) - 1);
}
// *loc[loc_start : loc_start + width] = value[value_start : value_start + width]
static void
set_bits(uint32_t *loc, uint8_t loc_start, uint64_t value, uint8_t value_start,
uint8_t width)
{
assert(loc_start + width <= 32);
// Clear the bits we're about to patch:
*loc &= ~(((1ULL << width) - 1) << loc_start);
assert(get_bits(*loc, loc_start, width) == 0);
// Patch the bits:
*loc |= get_bits(value, value_start, width) << loc_start;
assert(get_bits(*loc, loc_start, width) == get_bits(value, value_start, width));
}
// See https://developer.arm.com/documentation/ddi0602/2023-09/Base-Instructions
// for instruction encodings:
#define IS_AARCH64_ADD_OR_SUB(I) (((I) & 0x11C00000) == 0x11000000)
#define IS_AARCH64_ADRP(I) (((I) & 0x9F000000) == 0x90000000)
#define IS_AARCH64_BRANCH(I) (((I) & 0x7C000000) == 0x14000000)
#define IS_AARCH64_LDR_OR_STR(I) (((I) & 0x3B000000) == 0x39000000)
#define IS_AARCH64_MOV(I) (((I) & 0x9F800000) == 0x92800000)
// Fill all of stencil's holes in the memory pointed to by base, using the
// values in patches.
static void
patch(unsigned char *base, const Stencil *stencil, uintptr_t patches[])
{
for (size_t i = 0; i < stencil->holes_size; i++) {
const Hole *hole = &stencil->holes[i];
unsigned char *location = base + hole->offset;
uint64_t value = patches[hole->value] + (uintptr_t)hole->symbol + hole->addend;
uint8_t *loc8 = (uint8_t *)location;
uint32_t *loc32 = (uint32_t *)location;
uint64_t *loc64 = (uint64_t *)location;
// LLD is a great reference for performing relocations... just keep in
// mind that Tools/jit/build.py does filtering and preprocessing for us!
// Here's a good place to start for each platform:
// - aarch64-apple-darwin:
// - https://github.com/llvm/llvm-project/blob/main/lld/MachO/Arch/ARM64.cpp
// - https://github.com/llvm/llvm-project/blob/main/lld/MachO/Arch/ARM64Common.cpp
// - https://github.com/llvm/llvm-project/blob/main/lld/MachO/Arch/ARM64Common.h
// - aarch64-pc-windows-msvc:
// - https://github.com/llvm/llvm-project/blob/main/lld/COFF/Chunks.cpp
// - aarch64-unknown-linux-gnu:
// - https://github.com/llvm/llvm-project/blob/main/lld/ELF/Arch/AArch64.cpp
// - i686-pc-windows-msvc:
// - https://github.com/llvm/llvm-project/blob/main/lld/COFF/Chunks.cpp
// - x86_64-apple-darwin:
// - https://github.com/llvm/llvm-project/blob/main/lld/MachO/Arch/X86_64.cpp
// - x86_64-pc-windows-msvc:
// - https://github.com/llvm/llvm-project/blob/main/lld/COFF/Chunks.cpp
// - x86_64-unknown-linux-gnu:
// - https://github.com/llvm/llvm-project/blob/main/lld/ELF/Arch/X86_64.cpp
switch (hole->kind) {
case HoleKind_IMAGE_REL_I386_DIR32:
// 32-bit absolute address.
// Check that we're not out of range of 32 unsigned bits:
assert(value < (1ULL << 32));
*loc32 = (uint32_t)value;
continue;
case HoleKind_ARM64_RELOC_UNSIGNED:
case HoleKind_R_AARCH64_ABS64:
case HoleKind_X86_64_RELOC_UNSIGNED:
case HoleKind_R_X86_64_64:
// 64-bit absolute address.
*loc64 = value;
continue;
case HoleKind_IMAGE_REL_AMD64_REL32:
case HoleKind_IMAGE_REL_I386_REL32:
case HoleKind_R_X86_64_GOTPCRELX:
case HoleKind_R_X86_64_REX_GOTPCRELX:
case HoleKind_X86_64_RELOC_GOT:
case HoleKind_X86_64_RELOC_GOT_LOAD: {
// 32-bit relative address.
// Try to relax the GOT load into an immediate value:
uint64_t relaxed = *(uint64_t *)(value + 4) - 4;
if ((int64_t)relaxed - (int64_t)location >= -(1LL << 31) &&
(int64_t)relaxed - (int64_t)location + 1 < (1LL << 31))
{
if (loc8[-2] == 0x8B) {
// mov reg, dword ptr [rip + AAA] -> lea reg, [rip + XXX]
loc8[-2] = 0x8D;
value = relaxed;
}
else if (loc8[-2] == 0xFF && loc8[-1] == 0x15) {
// call qword ptr [rip + AAA] -> nop; call XXX
loc8[-2] = 0x90;
loc8[-1] = 0xE8;
value = relaxed;
}
else if (loc8[-2] == 0xFF && loc8[-1] == 0x25) {
// jmp qword ptr [rip + AAA] -> nop; jmp XXX
loc8[-2] = 0x90;
loc8[-1] = 0xE9;
value = relaxed;
}
}
}
// Fall through...
case HoleKind_R_X86_64_GOTPCREL:
case HoleKind_R_X86_64_PC32:
case HoleKind_X86_64_RELOC_SIGNED:
case HoleKind_X86_64_RELOC_BRANCH:
// 32-bit relative address.
value -= (uintptr_t)location;
// Check that we're not out of range of 32 signed bits:
assert((int64_t)value >= -(1LL << 31));
assert((int64_t)value < (1LL << 31));
*loc32 = (uint32_t)value;
continue;
case HoleKind_ARM64_RELOC_BRANCH26:
case HoleKind_IMAGE_REL_ARM64_BRANCH26:
case HoleKind_R_AARCH64_CALL26:
case HoleKind_R_AARCH64_JUMP26:
// 28-bit relative branch.
assert(IS_AARCH64_BRANCH(*loc32));
value -= (uintptr_t)location;
// Check that we're not out of range of 28 signed bits:
assert((int64_t)value >= -(1 << 27));
assert((int64_t)value < (1 << 27));
// Since instructions are 4-byte aligned, only use 26 bits:
assert(get_bits(value, 0, 2) == 0);
set_bits(loc32, 0, value, 2, 26);
continue;
case HoleKind_R_AARCH64_MOVW_UABS_G0_NC:
// 16-bit low part of an absolute address.
assert(IS_AARCH64_MOV(*loc32));
// Check the implicit shift (this is "part 0 of 3"):
assert(get_bits(*loc32, 21, 2) == 0);
set_bits(loc32, 5, value, 0, 16);
continue;
case HoleKind_R_AARCH64_MOVW_UABS_G1_NC:
// 16-bit middle-low part of an absolute address.
assert(IS_AARCH64_MOV(*loc32));
// Check the implicit shift (this is "part 1 of 3"):
assert(get_bits(*loc32, 21, 2) == 1);
set_bits(loc32, 5, value, 16, 16);
continue;
case HoleKind_R_AARCH64_MOVW_UABS_G2_NC:
// 16-bit middle-high part of an absolute address.
assert(IS_AARCH64_MOV(*loc32));
// Check the implicit shift (this is "part 2 of 3"):
assert(get_bits(*loc32, 21, 2) == 2);
set_bits(loc32, 5, value, 32, 16);
continue;
case HoleKind_R_AARCH64_MOVW_UABS_G3:
// 16-bit high part of an absolute address.
assert(IS_AARCH64_MOV(*loc32));
// Check the implicit shift (this is "part 3 of 3"):
assert(get_bits(*loc32, 21, 2) == 3);
set_bits(loc32, 5, value, 48, 16);
continue;
case HoleKind_ARM64_RELOC_GOT_LOAD_PAGE21:
case HoleKind_IMAGE_REL_ARM64_PAGEBASE_REL21:
case HoleKind_R_AARCH64_ADR_GOT_PAGE:
case HoleKind_R_AARCH64_ADR_PREL_PG_HI21:
// 21-bit count of pages between this page and an absolute address's
// page... I know, I know, it's weird. Pairs nicely with
// ARM64_RELOC_GOT_LOAD_PAGEOFF12 (below).
assert(IS_AARCH64_ADRP(*loc32));
// Try to relax the pair of GOT loads into an immediate value:
const Hole *next_hole = &stencil->holes[i + 1];
if (i + 1 < stencil->holes_size &&
(next_hole->kind == HoleKind_ARM64_RELOC_GOT_LOAD_PAGEOFF12 ||
next_hole->kind == HoleKind_IMAGE_REL_ARM64_PAGEOFFSET_12L ||
next_hole->kind == HoleKind_R_AARCH64_LD64_GOT_LO12_NC) &&
next_hole->offset == hole->offset + 4 &&
next_hole->symbol == hole->symbol &&
next_hole->addend == hole->addend &&
next_hole->value == hole->value)
{
unsigned char reg = get_bits(loc32[0], 0, 5);
assert(IS_AARCH64_LDR_OR_STR(loc32[1]));
// There should be only one register involved:
assert(reg == get_bits(loc32[1], 0, 5)); // ldr's output register.
assert(reg == get_bits(loc32[1], 5, 5)); // ldr's input register.
uint64_t relaxed = *(uint64_t *)value;
if (relaxed < (1UL << 16)) {
// adrp reg, AAA; ldr reg, [reg + BBB] -> movz reg, XXX; nop
loc32[0] = 0xD2800000 | (get_bits(relaxed, 0, 16) << 5) | reg;
loc32[1] = 0xD503201F;
i++;
continue;
}
if (relaxed < (1ULL << 32)) {
// adrp reg, AAA; ldr reg, [reg + BBB] -> movz reg, XXX; movk reg, YYY
loc32[0] = 0xD2800000 | (get_bits(relaxed, 0, 16) << 5) | reg;
loc32[1] = 0xF2A00000 | (get_bits(relaxed, 16, 16) << 5) | reg;
i++;
continue;
}
relaxed = value - (uintptr_t)location;
if ((relaxed & 0x3) == 0 &&
(int64_t)relaxed >= -(1L << 19) &&
(int64_t)relaxed < (1L << 19))
{
// adrp reg, AAA; ldr reg, [reg + BBB] -> ldr reg, XXX; nop
loc32[0] = 0x58000000 | (get_bits(relaxed, 2, 19) << 5) | reg;
loc32[1] = 0xD503201F;
i++;
continue;
}
}
// Fall through...
case HoleKind_ARM64_RELOC_PAGE21:
// Number of pages between this page and the value's page:
value = (value >> 12) - ((uintptr_t)location >> 12);
// Check that we're not out of range of 21 signed bits:
assert((int64_t)value >= -(1 << 20));
assert((int64_t)value < (1 << 20));
// value[0:2] goes in loc[29:31]:
set_bits(loc32, 29, value, 0, 2);
// value[2:21] goes in loc[5:26]:
set_bits(loc32, 5, value, 2, 19);
continue;
case HoleKind_ARM64_RELOC_GOT_LOAD_PAGEOFF12:
case HoleKind_ARM64_RELOC_PAGEOFF12:
case HoleKind_IMAGE_REL_ARM64_PAGEOFFSET_12A:
case HoleKind_IMAGE_REL_ARM64_PAGEOFFSET_12L:
case HoleKind_R_AARCH64_ADD_ABS_LO12_NC:
case HoleKind_R_AARCH64_LD64_GOT_LO12_NC:
// 12-bit low part of an absolute address. Pairs nicely with
// ARM64_RELOC_GOT_LOAD_PAGE21 (above).
assert(IS_AARCH64_LDR_OR_STR(*loc32) || IS_AARCH64_ADD_OR_SUB(*loc32));
// There might be an implicit shift encoded in the instruction:
uint8_t shift = 0;
if (IS_AARCH64_LDR_OR_STR(*loc32)) {
shift = (uint8_t)get_bits(*loc32, 30, 2);
// If both of these are set, the shift is supposed to be 4.
// That's pretty weird, and it's never actually been observed...
assert(get_bits(*loc32, 23, 1) == 0 || get_bits(*loc32, 26, 1) == 0);
}
value = get_bits(value, 0, 12);
assert(get_bits(value, 0, shift) == 0);
set_bits(loc32, 10, value, shift, 12);
continue;
}
Py_UNREACHABLE();
}
}
static void
copy_and_patch(unsigned char *base, const Stencil *stencil, uintptr_t patches[])
{
memcpy(base, stencil->body, stencil->body_size);
patch(base, stencil, patches);
}
static void
emit(const StencilGroup *group, uintptr_t patches[])
{
copy_and_patch((unsigned char *)patches[HoleValue_DATA], &group->data, patches);
copy_and_patch((unsigned char *)patches[HoleValue_CODE], &group->code, patches);
}
// Compiles executor in-place. Don't forget to call _PyJIT_Free later!
int
_PyJIT_Compile(_PyExecutorObject *executor, const _PyUOpInstruction *trace, size_t length)
{
// Loop once to find the total compiled size:
size_t instruction_starts[UOP_MAX_TRACE_LENGTH];
size_t code_size = 0;
size_t data_size = 0;
for (size_t i = 0; i < length; i++) {
_PyUOpInstruction *instruction = (_PyUOpInstruction *)&trace[i];
const StencilGroup *group = &stencil_groups[instruction->opcode];
instruction_starts[i] = code_size;
code_size += group->code.body_size;
data_size += group->data.body_size;
}
code_size += stencil_groups[_FATAL_ERROR].code.body_size;
data_size += stencil_groups[_FATAL_ERROR].data.body_size;
// Round up to the nearest page:
size_t page_size = get_page_size();
assert((page_size & (page_size - 1)) == 0);
size_t padding = page_size - ((code_size + data_size) & (page_size - 1));
size_t total_size = code_size + data_size + padding;
unsigned char *memory = jit_alloc(total_size);
if (memory == NULL) {
return -1;
}
// Loop again to emit the code:
unsigned char *code = memory;
unsigned char *data = memory + code_size;
assert(trace[0].opcode == _START_EXECUTOR || trace[0].opcode == _COLD_EXIT);
for (size_t i = 0; i < length; i++) {
_PyUOpInstruction *instruction = (_PyUOpInstruction *)&trace[i];
const StencilGroup *group = &stencil_groups[instruction->opcode];
// Think of patches as a dictionary mapping HoleValue to uintptr_t:
uintptr_t patches[] = GET_PATCHES();
patches[HoleValue_CODE] = (uintptr_t)code;
patches[HoleValue_CONTINUE] = (uintptr_t)code + group->code.body_size;
patches[HoleValue_DATA] = (uintptr_t)data;
patches[HoleValue_EXECUTOR] = (uintptr_t)executor;
patches[HoleValue_OPARG] = instruction->oparg;
#if SIZEOF_VOID_P == 8
patches[HoleValue_OPERAND] = instruction->operand;
#else
assert(SIZEOF_VOID_P == 4);
patches[HoleValue_OPERAND_HI] = instruction->operand >> 32;
patches[HoleValue_OPERAND_LO] = instruction->operand & UINT32_MAX;
#endif
switch (instruction->format) {
case UOP_FORMAT_TARGET:
patches[HoleValue_TARGET] = instruction->target;
break;
case UOP_FORMAT_EXIT:
assert(instruction->exit_index < executor->exit_count);
patches[HoleValue_EXIT_INDEX] = instruction->exit_index;
if (instruction->error_target < length) {
patches[HoleValue_ERROR_TARGET] = (uintptr_t)memory + instruction_starts[instruction->error_target];
}
break;
case UOP_FORMAT_JUMP:
assert(instruction->jump_target < length);
patches[HoleValue_JUMP_TARGET] = (uintptr_t)memory + instruction_starts[instruction->jump_target];
if (instruction->error_target < length) {
patches[HoleValue_ERROR_TARGET] = (uintptr_t)memory + instruction_starts[instruction->error_target];
}
break;
default:
assert(0);
Py_FatalError("Illegal instruction format");
}
patches[HoleValue_TOP] = (uintptr_t)memory + instruction_starts[1];
patches[HoleValue_ZERO] = 0;
emit(group, patches);
code += group->code.body_size;
data += group->data.body_size;
}
// Protect against accidental buffer overrun into data:
const StencilGroup *group = &stencil_groups[_FATAL_ERROR];
uintptr_t patches[] = GET_PATCHES();
patches[HoleValue_CODE] = (uintptr_t)code;
patches[HoleValue_CONTINUE] = (uintptr_t)code;
patches[HoleValue_DATA] = (uintptr_t)data;
patches[HoleValue_EXECUTOR] = (uintptr_t)executor;
patches[HoleValue_TOP] = (uintptr_t)code;
patches[HoleValue_ZERO] = 0;
emit(group, patches);
code += group->code.body_size;
data += group->data.body_size;
assert(code == memory + code_size);
assert(data == memory + code_size + data_size);
if (mark_executable(memory, total_size)) {
jit_free(memory, total_size);
return -1;
}
executor->jit_code = memory;
executor->jit_size = total_size;
return 0;
}
void
_PyJIT_Free(_PyExecutorObject *executor)
{
unsigned char *memory = (unsigned char *)executor->jit_code;
size_t size = executor->jit_size;
if (memory) {
executor->jit_code = NULL;
executor->jit_size = 0;
if (jit_free(memory, size)) {
PyErr_WriteUnraisable(NULL);
}
}
}
#endif // _Py_JIT
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