math: Fix UB in ldbl-128ibm llrintl

diff --git a/sysdeps/ieee754/ldbl-128ibm/s_llrintl.c b/sysdeps/ieee754/ldbl-128ibm/s_llrintl.c
index efc92558fcbe356b3e04ba165f2b52249908b53b..fb70cf8402b1a2ebdb0705a222ec6d177b2d92dd 100644 (file)
--- a/sysdeps/ieee754/ldbl-128ibm/s_llrintl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/s_llrintl.c
@@ -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;