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mesa: add u_overflow.h

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It defines a couple of helpers to deal with signed and unsigned
integers overflow.

If __builtin_add_overflow (and others) intrinics are available
they're used, otherwise overflow checks are done manually.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37331>
This commit is contained in:
Pierre-Eric Pelloux-Prayer 2025-09-12 11:34:24 +02:00
parent 66aefea02b
commit cfbf745a79
3 changed files with 90 additions and 0 deletions
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7
meson.build
View file

@ -1019,6 +1019,13 @@ foreach b : ['bswap32', 'bswap64', 'clz', 'clzll', 'ctz', 'expect', 'ffs',
endif
endforeach
# Check for GCC overflow intrinsics
foreach b : ['add_overflow', 'add_overflow_p', 'sub_overflow_p']
if cc.has_function('__builtin_' + b)
pre_args += '-DHAVE___BUILTIN_@0@'.format(b.to_upper())
endif
endforeach
# check for GCC __attribute__
_attributes = [
'const', 'flatten', 'malloc', 'pure', 'unused', 'warn_unused_result',

1
src/util/meson.build
View file

@ -165,6 +165,7 @@ files_mesa_util = files(
'u_cpu_detect.h',
'u_printf.c',
'u_printf.h',
'u_overflow.h',
'u_tristate.h',
'u_worklist.c',
'u_worklist.h',

82
src/util/u_overflow.h Normal file
View file

@ -0,0 +1,82 @@
/*
* Copyright © 2025 Advanced Micro Devices, Inc.
* SPDX-License-Identifier: MIT
*/
#include "util/macros.h"
#ifndef U_OVERFLOW_H
#define U_OVERFLOW_H
#ifdef HAVE___BUILTIN_ADD_OVERFLOW
#define util_add_overflow(ty, a, b, c) __builtin_add_overflow(a, b, c)
#else
#define DEFINE_U_ADD_OVERFLOW_UINT(ty) \
static inline bool \
util_add_overflow_##ty(ty a, ty b, ty * res) { \
*res = a + b; \
return *res < a; \
}
#define DEFINE_U_ADD_OVERFLOW_SINT(ty) \
static inline bool \
util_add_overflow_##ty(ty a, ty b, ty * res) { \
if ((b > 0 && a > u_intN_max(sizeof(a) * 8) - b) || \
(b < 0 && a < u_intN_min(sizeof(a) * 8) - b)) \
return true; \
*res = a + b; \
return false; \
}
DEFINE_U_ADD_OVERFLOW_UINT(size_t)
DEFINE_U_ADD_OVERFLOW_UINT(uint64_t)
DEFINE_U_ADD_OVERFLOW_SINT(int64_t)
#define util_add_overflow(ty, a, b, c) util_add_overflow_##ty(a, b, c)
#endif /* HAVE___BUILTIN_ADD_OVERFLOW */
#ifdef HAVE___BUILTIN_ADD_OVERFLOW_P
#define util_add_check_overflow(ty, a, b) __builtin_add_overflow_p(a, b, (ty)0)
#else
#define DEFINE_U_ADD_CHECK_OVERFLOW_UINT(ty) \
static inline bool \
util_add_check_overflow_##ty(ty a, ty b) { \
ty c = a + b; \
return c < a; \
}
#define DEFINE_U_ADD_CHECK_OVERFLOW_SINT(ty) \
static inline bool \
util_add_check_overflow_##ty(ty a, ty b) { \
return (b > 0 && a > u_intN_max(sizeof(a) * 8) - b) || \
(b < 0 && a < u_intN_min(sizeof(a) * 8) - b); \
}
DEFINE_U_ADD_CHECK_OVERFLOW_UINT(uint8_t)
DEFINE_U_ADD_CHECK_OVERFLOW_UINT(uint16_t)
DEFINE_U_ADD_CHECK_OVERFLOW_UINT(uint32_t)
DEFINE_U_ADD_CHECK_OVERFLOW_UINT(uint64_t)
DEFINE_U_ADD_CHECK_OVERFLOW_SINT(int8_t)
DEFINE_U_ADD_CHECK_OVERFLOW_SINT(int16_t)
DEFINE_U_ADD_CHECK_OVERFLOW_SINT(int32_t)
DEFINE_U_ADD_CHECK_OVERFLOW_SINT(int64_t)
#define util_add_check_overflow(ty, a, b) util_add_check_overflow_##ty(a, b)
#endif /* HAVE___BUILTIN_ADD_OVERFLOW_P */
#ifdef HAVE___BUILTIN_SUB_OVERFLOW_P
#define util_sub_check_overflow(ty, a, b) __builtin_sub_overflow_p(a, b, (ty)0)
#else
#define DEFINE_U_SUB_CHECK_OVERFLOW_SINT(ty) \
static inline bool \
util_sub_check_overflow_##ty(ty a, ty b) { \
return (b < 0 && a > u_intN_max(sizeof(a) * 8) + b) || \
(b > 0 && a < u_intN_min(sizeof(a) * 8) + b); \
}
DEFINE_U_SUB_CHECK_OVERFLOW_SINT(int8_t)
DEFINE_U_SUB_CHECK_OVERFLOW_SINT(int16_t)
DEFINE_U_SUB_CHECK_OVERFLOW_SINT(int32_t)
DEFINE_U_SUB_CHECK_OVERFLOW_SINT(int64_t)
#define util_sub_check_overflow(ty, a, b) util_sub_check_overflow_##ty(a, b)
#endif /* HAVE___BUILTIN_SUB_OVERFLOW_P */
#endif