Fix gen-auto-libm-tests sticky bit setting for negative results.

gen-auto-libm-tests has a bug in the logic for setting a sticky bit
based on the ternary value from MPFR: it is correct for positive
results, but for negative results mpz_setbit acts as if a two's
complement representation is used, whereas the low bit needs setting
based on the sign-magnitude representation GMP actually uses.  (This
showed up in converting fma tests to use auto-libm-test-in /
gen-auto-libm-tests.)

This patch fixes the problem by negating the mpz_t value to set its
low bit.  There are lots of changes to auto-libm-test-out (mainly 1ulp
fixes to ldbl-128 expected results), but only a few ulps updates are
needed on x86 / x86_64.  In one case, a corrected expectation showed
up a spurious underflow exception where the correct result is slightly
outside the underflowing range.

Tested x86_64 and x86 and ulps updated accordingly.

	* math/gen-auto-libm-tests.c (adjust_real): Ensure integers are
	non-negative before setting low bit.
	* math/auto-libm-test-in: Mark one asin test possibly having
	spurious underflow.
	* math/auto-libm-test-out: Regenerated.
	* sysdeps/i386/fpu/libm-test-ulps: Update.
	* sysdeps/x86_64/fpu/libm-test-ulps: Likewise.

1 files changed, 8 insertions, 1 deletions

diff --git a/math/gen-auto-libm-tests.c b/math/gen-auto-libm-tests.c
index 2f521d5c83..198d001519 100644
--- a/math/gen-auto-libm-tests.c
+++ b/math/gen-auto-libm-tests.c
@@ -987,7 +987,14 @@ adjust_real (mpfr_t r, bool inexact)
       mpz_t tmp;
       mpz_init (tmp);
       mpfr_exp_t e = mpfr_get_z_2exp (tmp, r);
-      mpz_setbit (tmp, 0);
+      if (mpz_sgn (tmp) < 0)
+	{
+	  mpz_neg (tmp, tmp);
+	  mpz_setbit (tmp, 0);
+	  mpz_neg (tmp, tmp);
+	}
+      else
+	mpz_setbit (tmp, 0);
       assert_exact (mpfr_set_z_2exp (r, tmp, e, MPFR_RNDN));
       mpz_clear (tmp);
     }