8000 Clean up the AArch64 stuff · python/cpython@6b19d7c · GitHub
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Clean up the AArch64 stuff
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‎Python/jit.c

Lines changed: 49 additions & 38 deletions
Original file line numberDiff line numberDiff line change
@@ -18,7 +18,7 @@
1818

1919
#include "jit_stencils.h"
2020

21-
// Boring memory management stuff //////////////////////////////////////////////
21+
// Memory management stuff: ////////////////////////////////////////////////////
2222

2323
#ifndef MS_WINDOWS
2424
#include <sys/mman.h>
@@ -130,28 +130,29 @@ mark_readable(char *memory, size_t size)
130130
return 0;
131131
}
132132

133-
// Cool JIT compiler stuff /////////////////////////////////////////////////////
133+
// JIT compiler stuff: /////////////////////////////////////////////////////////
134134

135135
// Warning! AArch64 requires you to get your hands dirty. These are your gloves:
136136

137137
// value[i : i + n]
138138
static uint32_t
139-
bits(uint64_t value, uint8_t i, uint8_t n)
139+
get_bits(uint64_t value, uint8_t i, uint8_t n)
140140
{
141141
assert(n <= 32);
142142
return (value >> i) & ((1ULL << n) - 1);
143143
}
144144

145-
// *loc[j : j + n] = value[i : i + n]
145+
// *loc[i : i + n] = value[j : j + n]
146146
static void
147-
patch_bits(uint32_t *loc, uint64_t value, uint8_t i, uint8_t n, uint8_t j)
147+
set_bits(uint32_t *loc, uint8_t i, uint8_t n, uint64_t value, uint8_t j)
148148
{
149-
assert(j + n <= 32);
149+
assert(i + n <= 32);
150150
// Clear the bits we're about to patch:
151-
*loc &= ~(((1ULL << n) - 1) << j);
152-
assert(bits(*loc, j, n) == 0);
151+
*loc &= ~(((1ULL << n) - 1) << i);
152+
assert(get_bits(*loc, i, n) == 0);
153153
// Patch the bits:
154-
*loc |= bits(value, i, n) << j;
154+
*loc |= get_bits(value, j, n) << i;
155+
assert(get_bits(*loc, i, n) == get_bits(value, j, n));
155156
}
156157

157158
// See https://developer.arm.com/documentation/ddi0602/2023-09/Base-Instructions
@@ -165,12 +166,19 @@ patch_bits(uint32_t *loc, uint64_t value, uint8_t i, uint8_t n, uint8_t j)
165166
// LLD is an awesome reference for how to perform relocations... just keep in
166167
// mind that Tools/jit/build.py does some filtering and preprocessing for us!
167168
// Here's a good place to start for each platform:
168-
// - aarch64-apple-darwin: https://github.com/llvm/llvm-project/blob/main/lld/MachO/Arch/ARM64Common.cpp
169-
// - aarch64-unknown-linux-gnu: https://github.com/llvm/llvm-project/blob/main/lld/ELF/Arch/AArch64.cpp
170-
// - i686-pc-windows-msvc: https://github.com/llvm/llvm-project/blob/main/lld/COFF/Chunks.cpp
171-
// - x86_64-apple-darwin: https://github.com/llvm/llvm-project/blob/main/lld/MachO/Arch/X86_64.cpp
172-
// - x86_64-pc-windows-msvc: https://github.com/llvm/llvm-project/blob/main/lld/COFF/Chunks.cpp
173-
// - x86_64-unknown-linux-gnu: https://github.com/llvm/llvm-project/blob/main/lld/ELF/Arch/AArch64.cpp
169+
// - aarch64-apple-darwin:
170+
// - https://github.com/llvm/llvm-project/blob/main/lld/MachO/Arch/ARM64Common.cpp
171+
// - https://github.com/llvm/llvm-project/blob/main/lld/MachO/Arch/ARM64Common.h
172+
// - aarch64-unknown-linux-gnu:
173+
// - https://github.com/llvm/llvm-project/blob/main/lld/ELF/Arch/AArch64.cpp
174+
// - i686-pc-windows-msvc:
175+
// - https://github.com/llvm/llvm-project/blob/main/lld/COFF/Chunks.cpp
176+
// - x86_64-apple-darwin:
177+
// - https://github.com/llvm/llvm-project/blob/main/lld/MachO/Arch/X86_64.cpp
178+
// - x86_64-pc-windows-msvc:
179+
// - https://github.com/llvm/llvm-project/blob/main/lld/COFF/Chunks.cpp
180+
// - x86_64-unknown-linux-gnu:
181+
// - https://github.com/llvm/llvm-project/blob/main/lld/ELF/Arch/X86_64.cpp
174182
static void
175183
patch(char *base, const Hole *hole, uint64_t *patches)
176184
{
@@ -202,50 +210,51 @@ patch(char *base, const Hole *hole, uint64_t *patches)
202210
assert((int64_t)value >= -(1 << 27));
203211
assert((int64_t)value < (1 << 27));
204212
// Since instructions are 4-byte aligned, only use 26 bits:
205-
assert(bits(value, 0, 2) == 0);
206-
patch_bits(loc32, value, 2, 26, 0);
213+
assert(get_bits(value, 0, 2) == 0);
214+
set_bits(loc32, 0, 26, value, 2);
207215
return;
208216
case HoleKind_R_AARCH64_MOVW_UABS_G0_NC:
209217
// 16-bit low part of an absolute address.
210218
assert(IS_AARCH64_MOV(*loc32));
211219
// Check the implicit shift (this is "part 0 of 3"):
212-
assert(bits(*loc32, 21, 2) == 0);
213-
patch_bits(loc32, value, 0, 16, 5);
220+
assert(get_bits(*loc32, 21, 2) == 0);
221+
set_bits(loc32, 5, 16, value, 0);
214222
return;
215223
case HoleKind_R_AARCH64_MOVW_UABS_G1_NC:
216224
// 16-bit middle-low part of an absolute address.
217225
assert(IS_AARCH64_MOV(*loc32));
218226
// Check the implicit shift (this is "part 1 of 3"):
219-
assert(bits(*loc32, 21, 2) == 1);
220-
patch_bits(loc32, value, 16, 16, 5);
227+
assert(get_bits(*loc32, 21, 2) == 1);
228+
set_bits(loc32, 5, 16, value, 16);
221229
return;
222230
case HoleKind_R_AARCH64_MOVW_UABS_G2_NC:
223231
// 16-bit middle-high part of an absolute address.
224232
assert(IS_AARCH64_MOV(*loc32));
225233
// Check the implicit shift (this is "part 2 of 3"):
226-
assert(bits(*loc32, 21, 2) == 2);
227-
patch_bits(loc32, value, 32, 16, 5);
234+
assert(get_bits(*loc32, 21, 2) == 2);
235+
set_bits(loc32, 5, 16, value, 32);
228236
return;
229237
case HoleKind_R_AARCH64_MOVW_UABS_G3:
230238
// 16-bit high part of an absolute address.
231239
assert(IS_AARCH64_MOV(*loc32));
232240
// Check the implicit shift (this is "part 3 of 3"):
233-
assert(bits(*loc32, 21, 2) == 3);
234-
patch_bits(loc32, value, 48, 16, 5);
241+
assert(get_bits(*loc32, 21, 2) == 3);
242+
set_bits(loc32, 5, 16, value, 48);
235243
return;
236244
case HoleKind_ARM64_RELOC_GOT_LOAD_PAGE21:
237245
// 21-bit count of pages between this page and an absolute address's
238246
// page... I know, I know, it's weird. Pairs nicely with
239247
// ARM64_RELOC_GOT_LOAD_PAGEOFF12 (below).
240248
assert(IS_AARCH64_ADRP(*loc32));
241-
// The high 31 bits are ignored, so they must match:
242-
assert(bits(value, 33, 31) == bits((uint64_t)location, 33, 31));
243249
// Number of pages between this page and the value's page:
244-
value = bits(value, 12, 21) - bits((uint64_t)location, 12, 21);
250+
value = (value >> 12) - ((uint64_t)location >> 12);
251+
// Check that we're not out of range of 21 signed bits:
252+
assert((int64_t)value >= -(1 << 20));
253+
assert((int64_t)value < (1 << 20));
245254
// value[0:2] goes in loc[29:31]:
246-
patch_bits(loc32, value, 0, 2, 29);
255+
set_bits(loc32, 29, 2, value, 0);
247256
// value[2:21] goes in loc[5:26]:
248-
patch_bits(loc32, value, 2, 19, 5);
257+
set_bits(loc32, 5, 19, value, 2);
249258
return;
250259
case HoleKind_ARM64_RELOC_GOT_LOAD_PAGEOFF12:
251260
// 12-bit low part of an absolute address. Pairs nicely with
@@ -254,14 +263,14 @@ patch(char *base, const Hole *hole, uint64_t *patches)
254263
// There might be an implicit shift encoded in the instruction:
255264
uint8_t shift = 0;
256265
if (IS_AARCH64_LDR_OR_STR(*loc32)) {
257-
shift = (uint8_t)bits(*loc32, 30, 2);
266+
shift = (uint8_t)get_bits(*loc32, 30, 2);
258267
// If both of these are set, the shift is supposed to be 4.
259268
// That's pretty weird, and it's never actually been observed...
260-
assert(bits(*loc32, 23, 1) == 0 || bits(*loc32, 26, 1) == 0);
269+
assert(get_bits(*loc32, 23, 1) == 0 || get_bits(*loc32, 26, 1) == 0);
261270
}
262-
value = bits(value, 0, 12);
263-
assert(bits(value, 0, shift) == 0);
264-
patch_bits(loc32, value, shift, 12, 10);
271+
value = get_bits(value, 0, 12);
272+
assert(get_bits(value, 0, shift) == 0);
273+
set_bits(loc32, 10, 12, value, shift);
265274
return;
266275
}
267276
Py_UNREACHABLE();
@@ -287,7 +296,8 @@ emit(const StencilGroup *stencil_group, uint64_t patches[])
287296

288297
// This becomes the executor's execute member, and handles some setup/teardown:
289298
static _Py_CODEUNIT *
290-
execute(_PyExecutorObject *executor, _PyInterpreterFrame *frame, PyObject **stack_pointer)
299+
execute(_PyExecutorObject *executor, _PyInterpreterFrame *frame,
300+
PyObject **stack_pointer)
291301
{
292302
PyThreadState *tstate = PyThreadState_Get();
293303
assert(PyObject_TypeCheck(executor, &_PyUOpExecutor_Type));
@@ -340,8 +350,9 @@ _PyJIT_Compile(_PyUOpExecutorObject *executor)
340350
text += stencil_group->text.body_size;
341351
data += stencil_group->data.body_size;
342352
}
343-
// Change the permissions... DO NOT LEAVE ANYTHING WRITABLE!
344-
if (mark_executable(memory, text_size) || mark_readable(memory + text_size, data_size)) {
353+
if (mark_executable(memory, text_size) ||
354+
mark_readable(memory + text_size, data_size))
355+
{
345356
jit_free(memory, text_size + data_size);
346357
goto fail;
347358
}

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