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math: Fix UB in ldbl-128ibm llrintl

This commit is contained in:
Adhemerval Zanella 2025-05-08 12:20:21 +00:00
parent 5ae9c869b0
commit 673776c7be
1 changed files with 19 additions and 10 deletions
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29
sysdeps/ieee754/ldbl-128ibm/s_llrintl.c
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@ -23,13 +23,20 @@
#include <math_ldbl_opt.h>
#include <float.h>
#include <ieee754.h>
#include <intprops.h>
static inline bool
check_sign (unsigned long int v1, unsigned long int v2)
{
enum { sign_shift = sizeof (unsigned long long int) * CHAR_BIT - 1 };
return (v1 & (1UL << sign_shift)) == (v2 & (1UL << sign_shift));
}
long long
__llrintl (long double x)
{
double xh, xl;
long long res, hi, lo;
long long res, hi, lo, tmp;
int save_round;
ldbl_unpack (x, &xh, &xl);
@ -70,10 +77,11 @@ __llrintl (long double x)
/* Peg at max/min values, assuming that the above conversions do so.
Strictly speaking, we can return anything for values that overflow,
but this is more useful. */
res = hi + lo;
INT_ADD_WRAPV (hi, lo, &res);
/* This is just sign(hi) == sign(lo) && sign(res) != sign(hi). */
if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
//if (__glibc_unlikely (((~(hi ^ lo) & (res ^ hi)) < 0)))
if (__glibc_unlikely (check_sign (hi, lo) && !check_sign (res, hi)))
goto overflow;
xh -= lo;
@ -91,31 +99,32 @@ __llrintl (long double x)
return res;
if (xh < 0.0)
res -= 1;
INT_SUBTRACT_WRAPV (res, 1, &res);
else
res += 1;
INT_ADD_WRAPV (res, 1, &res);
break;
case FE_TOWARDZERO:
if (res > 0 && (xh < 0.0 || (xh == 0.0 && xl < 0.0)))
res -= 1;
INT_SUBTRACT_WRAPV (res, 1, &res);
else if (res < 0 && (xh > 0.0 || (xh == 0.0 && xl > 0.0)))
res += 1;
INT_ADD_WRAPV (res, 1, &res);
return res;
break;
case FE_UPWARD:
if (xh > 0.0 || (xh == 0.0 && xl > 0.0))
res += 1;
INT_ADD_WRAPV (res, 1, &res);
break;
case FE_DOWNWARD:
if (xh < 0.0 || (xh == 0.0 && xl < 0.0))
res -= 1;
INT_SUBTRACT_WRAPV (res, 1, &res);
break;
}
if (__glibc_unlikely (((~(hi ^ (res - hi)) & (res ^ hi)) < 0)))
INT_SUBTRACT_WRAPV (res, hi, &tmp);
if (__glibc_unlikely (check_sign (hi, tmp) && !check_sign (res, hi)))
goto overflow;
return res;