mesa: add u_overflow.h

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>

src/util/meson.build

@@ -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',

src/util/u_overflow.h

@@ -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