cpython/Python/jit.c at 9b8611eeea172cd4aa626ccd1ca333dc4093cd8c · python/cpython · GitHub

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#ifdef _Py_JIT

#include "Python.h"

#include "pycore_abstract.h"

#include "pycore_call.h"

#include "pycore_ceval.h"

#include "pycore_critical_section.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"

// 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)

// 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

// Many of these patches are "relaxing", meaning that they can rewrite the

// code they're patching to be more efficient (like turning a 64-bit memory

// load into a 32-bit immediate load). These patches have an "x" in their name.

// Relative patches have an "r" in their name.

// 32-bit absolute address.

void

patch_32(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

// Check that we're not out of range of 32 unsigned bits:

assert(value < (1ULL << 32));

*loc32 = (uint32_t)value;

}

// 32-bit relative address.

void

patch_32r(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

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;

}

// 64-bit absolute address.

void

patch_64(unsigned char *location, uint64_t value)

{

uint64_t *loc64 = (uint64_t *)location;

*loc64 = value;

}

// 12-bit low part of an absolute address. Pairs nicely with patch_aarch64_21r

// (below).

void

patch_aarch64_12(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

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);

}

// Relaxable 12-bit low part of an absolute address. Pairs nicely with

// patch_aarch64_21rx (below).

void

patch_aarch64_12x(unsigned char *location, uint64_t value)

{

// This can *only* be relaxed if it occurs immediately before a matching

// patch_aarch64_21rx. If that happens, the JIT build step will replace both

// calls with a single call to patch_aarch64_33rx. Otherwise, we end up

// here, and the instruction is patched normally:

patch_aarch64_12(location, value);

}

// 16-bit low part of an absolute address.

void

patch_aarch64_16a(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

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);

}

// 16-bit middle-low part of an absolute address.

void

patch_aarch64_16b(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

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);

}

// 16-bit middle-high part of an absolute address.

void

patch_aarch64_16c(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

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);

}

// 16-bit high part of an absolute address.

void

patch_aarch64_16d(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

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);

}

// 21-bit count of pages between this page and an absolute address's page... I

// know, I know, it's weird. Pairs nicely with patch_aarch64_12 (above).

void

patch_aarch64_21r(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

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);

}

// Relaxable 21-bit count of pages between this page and an absolute address's

// page. Pairs nicely with patch_aarch64_12x (above).

void

patch_aarch64_21rx(unsigned char *location, uint64_t value)

{

// This can *only* be relaxed if it occurs immediately before a matching

// patch_aarch64_12x. If that happens, the JIT build step will replace both

// calls with a single call to patch_aarch64_33rx. Otherwise, we end up

// here, and the instruction is patched normally:

patch_aarch64_21r(location, value);

}

// 28-bit relative branch.

void

patch_aarch64_26r(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

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);

}

// A pair of patch_aarch64_21rx and patch_aarch64_12x.

void

patch_aarch64_33rx(unsigned char *location, uint64_t value)

{

uint32_t *loc32 = (uint32_t *)location;

// Try to relax the pair of GOT loads into an immediate value:

assert(IS_AARCH64_ADRP(*loc32));

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;

return;

}

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;

return;

}

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;

return;

}

// Couldn't do it. Just patch the two instructions normally:

patch_aarch64_21rx(location, value);

patch_aarch64_12x(location + 4, value);

}

// Relaxable 32-bit relative address.

void

patch_x86_64_32rx(unsigned char *location, uint64_t value)

{

uint8_t *loc8 = (uint8_t *)location;

// 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;

}

patch_32r(location, value);

}

#include "jit_stencils.h"

// Compiles executor in-place. Don't forget to call _PyJIT_Free later!

int

_PyJIT_Compile(_PyExecutorObject *executor, const _PyUOpInstruction trace[], size_t length)

{

const StencilGroup *group;

// Loop once to find the total compiled size:

uintptr_t instruction_starts[UOP_MAX_TRACE_LENGTH];

size_t code_size = 0;

size_t data_size = 0;

group = &trampoline;

code_size += group->code_size;

data_size += group->data_size;

for (size_t i = 0; i < length; i++) {

const _PyUOpInstruction *instruction = &trace[i];

group = &stencil_groups[instruction->opcode];

instruction_starts[i] = code_size;

code_size += group->code_size;

data_size += group->data_size;

}

group = &stencil_groups[_FATAL_ERROR];

code_size += group->code_size;

data_size += group->data_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;

}

// Update the offsets of each instruction:

for (size_t i = 0; i < length; i++) {

instruction_starts[i] += (uintptr_t)memory;

}

// Loop again to emit the code:

unsigned char *code = memory;

unsigned char *data = memory + code_size;

// Compile the trampoline, which handles converting between the native

// calling convention and the calling convention used by jitted code

// (which may be different for efficiency reasons). On platforms where

// we don't change calling conventions, the trampoline is empty and

// nothing is emitted here:

group = &trampoline;

group->emit(code, data, executor, NULL, instruction_starts);

code += group->code_size;

data += group->data_size;

assert(trace[0].opcode == _START_EXECUTOR || trace[0].opcode == _COLD_EXIT);

for (size_t i = 0; i < length; i++) {

const _PyUOpInstruction *instruction = &trace[i];

group = &stencil_groups[instruction->opcode];

group->emit(code, data, executor, instruction, instruction_starts);

code += group->code_size;

data += group->data_size;

}

// Protect against accidental buffer overrun into data:

group = &stencil_groups[_FATAL_ERROR];

group->emit(code, data, executor, NULL, instruction_starts);

code += group->code_size;

data += group->data_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_side_entry = memory + trampoline.code_size;

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_side_entry = NULL;

executor->jit_size = 0;

if (jit_free(memory, size)) {

PyErr_WriteUnraisable(NULL);

}

#endif // _Py_JIT

cpython/Python/jit.c at 9b8611eeea172cd4aa626ccd1ca333dc4093cd8c · python/cpython · GitHub

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