[glibc] math: Fix exp10 undefined left shift

[glibc] math: Fix exp10 undefined left shift

[Szabolcs Nagy]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=2a9943b4a03b6bce7c2b1b047592eee38ab74fab

commit 2a9943b4a03b6bce7c2b1b047592eee38ab74fab
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Wed May 22 16:33:43 2024 +0100

    math: Fix exp10 undefined left shift
    
    Left shift of ki is undefined when ki<0, copy the logic from exp,
    which uses unsigned arithmetics, to fix it.
    
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

Diff:
---
 sysdeps/ieee754/dbl-64/e_exp10.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sysdeps/ieee754/dbl-64/e_exp10.c b/sysdeps/ieee754/dbl-64/e_exp10.c
index 225fc74c4c..7ea8270063 100644
--- a/sysdeps/ieee754/dbl-64/e_exp10.c
+++ b/sysdeps/ieee754/dbl-64/e_exp10.c
@@ -38,7 +38,7 @@ special_case (uint64_t sbits, double_t tmp, uint64_t ki)
 {
   double_t scale, y;
 
-  if (ki - (1ull << 16) < 0x80000000)
+  if ((ki & 0x80000000) == 0)
     {
       /* The exponent of scale might have overflowed by 1.  */
       sbits -= 1ull << 52;
@@ -100,14 +100,14 @@ __exp10 (double x)
   /* Reduce x: z = x * N / log10(2), k = round(z).  */
   double_t z = __exp_data.invlog10_2N * x;
   double_t kd;
-  int64_t ki;
+  uint64_t ki;
 #if TOINT_INTRINSICS
   kd = roundtoint (z);
   ki = converttoint (z);
 #else
   kd = math_narrow_eval (z + Shift);
+  ki = asuint64 (kd);
   kd -= Shift;
-  ki = kd;
 #endif
 
   /* r = x - k * log10(2), r in [-0.5, 0.5].  */