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softfloat: make sign bit an unsigned int

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According to ubsan shifting an int32_t by 31 bits to the left is undefined
behavior. So just declare it as uint32_t.

Backport-to: 26.1
Reviewed-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
(cherry picked from commit b2aa92b523)

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41402>
This commit is contained in:
Karol Herbst 2026-04-29 01:39:41 +02:00 • committed by Eric Engestrom
parent 5d40635bc8
commit 7116d2fed0
2 changed files with 6 additions and 4 deletions
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2
.pick_status.json
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@ -3064,7 +3064,7 @@
"description": "softfloat: make sign bit an unsigned int",
"nominated": true,
"nomination_type": 4,
"resolution": 0,
"resolution": 1,
"main_sha": null,
"because_sha": null,
"notes": null

8
src/util/softfloat.c
View file

@ -153,7 +153,7 @@ double _mesa_roundtozero_f64(int64_t s, int64_t e, int64_t m)
* \brief Extracted from softfloat_roundPackToF32()
*/
static inline
float _mesa_round_f32(int32_t s, int32_t e, int32_t m, bool rtz)
float _mesa_round_f32(uint32_t s, int32_t e, int32_t m, bool rtz)
{
fi_type result;
uint8_t round_increment = rtz ? 0 : 0x40;
@ -1192,7 +1192,8 @@ _mesa_float_fma_rtz(float a, float b, float c)
uint32_t c_flt_m = c_fi.u & 0x07fffff;
uint32_t c_flt_e = (c_fi.u >> 23) & 0xff;
uint32_t c_flt_s = (c_fi.u >> 31) & 0x1;
int32_t s, e, m = 0;
uint32_t s;
int32_t e, m = 0;
c_flt_s ^= 0;
s = a_flt_s ^ b_flt_s ^ 0;
@ -1371,7 +1372,8 @@ _mesa_double_to_f32(double val, bool rtz)
uint64_t flt_m = di.u & 0x0fffffffffffff;
uint64_t flt_e = (di.u >> 52) & 0x7ff;
uint64_t flt_s = (di.u >> 63) & 0x1;
int32_t s, e, m = 0;
uint32_t s;
int32_t e, m = 0;
s = flt_s;