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Fix maybe-uninitialized error on powerpc

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The build has been failing on powerpc64le-linux-gnu with GCC 10
due to a maybe-uninitialized error:

../sysdeps/ieee754/dbl-64/mpa.c:875:6: error: ‘w.e’ may be used
uninitialized in this function [-Werror=maybe-uninitialized]
  875 |   EY -= EX;
      |      ^~

The warning is thrown because when __inv is called by __dvd *y is not
initialized and if t == 0 before calling __dbl_mp, EY will stay
uninitialized, as the function does not touch it in this case.

However, since t will be set to 1/t before calling __dbl_mp, t == 0 will
never happen, so we can instruct the compiler to ignore this case, which
suppresses the warning.

Tested on powerpc64le.

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
This commit is contained in:
Matheus Castanho 2020-01-17 11:44:54 -03:00 committed by Tulio Magno Quites Machado Filho
parent be5c5315b9
commit 9f8b135f76
1 changed files with 7 additions and 0 deletions
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7
sysdeps/ieee754/dbl-64/mpa.c
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@ -871,6 +871,13 @@ __inv (const mp_no *x, mp_no *y, int p)
z.e = 0;
__mp_dbl (&z, &t, p);
t = 1 / t;
/* t == 0 will never happen at this point, since 1/t can only be 0 if t is
infinity, but before the division t == mantissa of x (exponent is 0). We
can instruct the compiler to ignore this case. */
if (t == 0)
__builtin_unreachable ();
__dbl_mp (t, y, p);
EY -= EX;