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authorJoseph Myers <joseph@codesourcery.com>2015-09-25 22:29:10 +0000
committerJoseph Myers <joseph@codesourcery.com>2015-09-25 22:29:10 +0000
commit6ace39382120dd0668b2168591611f71b04ac8f3 (patch)
tree2cee18351450bd4f9586f033cae63aa4d1ec8d4d /sysdeps/ieee754
parent5a9af6376d43b58c6545feb86002812a57956654 (diff)
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Fix pow missing underflows (bug 18825).
Similar to various other bugs in this area, pow functions can fail to raise the underflow exception when the result is tiny and inexact but one or more low bits of the intermediate result that is scaled down (or, in the i386 case, converted from a wider evaluation format) are zero. This patch forces the exception in a similar way to previous fixes, thereby concluding the fixes for known bugs with missing underflow exceptions currently filed in Bugzilla. Tested for x86_64, x86, mips64 and powerpc. [BZ #18825] * sysdeps/i386/fpu/i386-math-asm.h (FLT_NARROW_EVAL_UFLOW_NONNAN): New macro. (DBL_NARROW_EVAL_UFLOW_NONNAN): Likewise. (LDBL_CHECK_FORCE_UFLOW_NONNAN): Likewise. * sysdeps/i386/fpu/e_pow.S: Use DEFINE_DBL_MIN. (__ieee754_pow): Use DBL_NARROW_EVAL_UFLOW_NONNAN instead of DBL_NARROW_EVAL, reloading the PIC register as needed. * sysdeps/i386/fpu/e_powf.S: Use DEFINE_FLT_MIN. (__ieee754_powf): Use FLT_NARROW_EVAL_UFLOW_NONNAN instead of FLT_NARROW_EVAL. Use separate return path for case when first argument is NaN. * sysdeps/i386/fpu/e_powl.S: Include <i386-math-asm.h>. Use DEFINE_LDBL_MIN. (__ieee754_powl): Use LDBL_CHECK_FORCE_UFLOW_NONNAN, reloading the PIC register. * sysdeps/ieee754/dbl-64/e_pow.c (__ieee754_pow): Use math_check_force_underflow_nonneg. * sysdeps/ieee754/flt-32/e_powf.c (__ieee754_powf): Force underflow for subnormal result. * sysdeps/ieee754/ldbl-128/e_powl.c (__ieee754_powl): Likewise. * sysdeps/ieee754/ldbl-128ibm/e_powl.c (__ieee754_powl): Use math_check_force_underflow_nonneg. * sysdeps/x86/fpu/powl_helper.c (__powl_helper): Use math_check_force_underflow. * sysdeps/x86_64/fpu/x86_64-math-asm.h (LDBL_CHECK_FORCE_UFLOW_NONNAN): New macro. * sysdeps/x86_64/fpu/e_powl.S: Include <x86_64-math-asm.h>. Use DEFINE_LDBL_MIN. (__ieee754_powl): Use LDBL_CHECK_FORCE_UFLOW_NONNAN. * math/auto-libm-test-in: Add more tests of pow. * math/auto-libm-test-out: Regenerated.
Diffstat (limited to 'sysdeps/ieee754')
-rw-r--r--sysdeps/ieee754/dbl-64/e_pow.c2
-rw-r--r--sysdeps/ieee754/flt-32/e_powf.c7
-rw-r--r--sysdeps/ieee754/ldbl-128/e_powl.c6
-rw-r--r--sysdeps/ieee754/ldbl-128ibm/e_powl.c1
4 files changed, 14 insertions, 2 deletions
diff --git a/sysdeps/ieee754/dbl-64/e_pow.c b/sysdeps/ieee754/dbl-64/e_pow.c
index 3c027fe..3b0bbe3 100644
--- a/sysdeps/ieee754/dbl-64/e_pow.c
+++ b/sysdeps/ieee754/dbl-64/e_pow.c
@@ -119,6 +119,8 @@ __ieee754_pow (double x, double y)
retval = huge * huge;
else if (retval == 0)
retval = tiny * tiny;
+ else
+ math_check_force_underflow_nonneg (retval);
return retval;
}
diff --git a/sysdeps/ieee754/flt-32/e_powf.c b/sysdeps/ieee754/flt-32/e_powf.c
index 8e8d918..1804296 100644
--- a/sysdeps/ieee754/flt-32/e_powf.c
+++ b/sysdeps/ieee754/flt-32/e_powf.c
@@ -244,7 +244,12 @@ __ieee754_powf(float x, float y)
z = one-(r-z);
GET_FLOAT_WORD(j,z);
j += (n<<23);
- if((j>>23)<=0) z = __scalbnf(z,n); /* subnormal output */
+ if((j>>23)<=0) /* subnormal output */
+ {
+ z = __scalbnf (z, n);
+ float force_underflow = z * z;
+ math_force_eval (force_underflow);
+ }
else SET_FLOAT_WORD(z,j);
return s*z;
}
diff --git a/sysdeps/ieee754/ldbl-128/e_powl.c b/sysdeps/ieee754/ldbl-128/e_powl.c
index f531385..7f3037f 100644
--- a/sysdeps/ieee754/ldbl-128/e_powl.c
+++ b/sysdeps/ieee754/ldbl-128/e_powl.c
@@ -435,7 +435,11 @@ __ieee754_powl (long double x, long double y)
j = o.parts32.w0;
j += (n << 16);
if ((j >> 16) <= 0)
- z = __scalbnl (z, n); /* subnormal output */
+ {
+ z = __scalbnl (z, n); /* subnormal output */
+ long double force_underflow = z * z;
+ math_force_eval (force_underflow);
+ }
else
{
o.parts32.w0 = j;
diff --git a/sysdeps/ieee754/ldbl-128ibm/e_powl.c b/sysdeps/ieee754/ldbl-128ibm/e_powl.c
index c942f2f..90340e8 100644
--- a/sysdeps/ieee754/ldbl-128ibm/e_powl.c
+++ b/sysdeps/ieee754/ldbl-128ibm/e_powl.c
@@ -409,6 +409,7 @@ __ieee754_powl (long double x, long double y)
r = (z * t1) / (t1 - two) - (w + z * w);
z = one - (r - z);
z = __scalbnl (z, n);
+ math_check_force_underflow_nonneg (z);
return s * z;
}
strong_alias (__ieee754_powl, __powl_finite)