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Fix hypot missing underflows (bug 18803).

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Similar to various other bugs in this area, hypot 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.

Note that this issue cannot arise for implementations of hypotf using
double (or wider) for intermediate evaluation (if hypotf should
underflow, that means the double square root is being computed of some
number of the form N*2^-298, for 0 < N < 2^46, which is exactly
represented as a double, and whatever the rounding mode such a square
root cannot have a mantissa with all zeroes after the initial 23
bits).  Thus no changes are made to hypotf implementations in this
patch, only to hypot and hypotl.

Tested for x86_64, x86, mips64 and powerpc.

	[BZ #18803]
	* sysdeps/i386/fpu/e_hypot.S: Use DEFINE_DBL_MIN.
	(MO): New macro.
	(__ieee754_hypot) [PIC]: Load PIC register.
	(__ieee754_hypot): Use DBL_NARROW_EVAL_UFLOW_NONNEG instead of
	DBL_NARROW_EVAL.
	* sysdeps/ieee754/dbl-64/e_hypot.c (__ieee754_hypot): Use
	math_check_force_underflow_nonneg in case where result might be
	tiny.
	* sysdeps/ieee754/ldbl-128/e_hypotl.c (__ieee754_hypotl):
	Likewise.
	* sysdeps/ieee754/ldbl-128ibm/e_hypotl.c (__ieee754_hypotl):
	Likewise.
	* sysdeps/ieee754/ldbl-96/e_hypotl.c (__ieee754_hypotl): Likewise.
	* sysdeps/powerpc/fpu/e_hypot.c (__ieee754_hypot): Likewise.
	* math/auto-libm-test-in: Add more tests of hypot.
	* math/auto-libm-test-out: Regenerated.
This commit is contained in:
Joseph Myers 2015-09-24 23:43:57 +00:00
parent 2fd9177c92
commit f6987f5aa4
10 changed files with 1401 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
ChangeLog
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@ -1,3 +1,23 @@
2015-09-24 Joseph Myers <joseph@codesourcery.com>
[BZ #18803]
* sysdeps/i386/fpu/e_hypot.S: Use DEFINE_DBL_MIN.
(MO): New macro.
(__ieee754_hypot) [PIC]: Load PIC register.
(__ieee754_hypot): Use DBL_NARROW_EVAL_UFLOW_NONNEG instead of
DBL_NARROW_EVAL.
* sysdeps/ieee754/dbl-64/e_hypot.c (__ieee754_hypot): Use
math_check_force_underflow_nonneg in case where result might be
tiny.
* sysdeps/ieee754/ldbl-128/e_hypotl.c (__ieee754_hypotl):
Likewise.
* sysdeps/ieee754/ldbl-128ibm/e_hypotl.c (__ieee754_hypotl):
Likewise.
* sysdeps/ieee754/ldbl-96/e_hypotl.c (__ieee754_hypotl): Likewise.
* sysdeps/powerpc/fpu/e_hypot.c (__ieee754_hypot): Likewise.
* math/auto-libm-test-in: Add more tests of hypot.
* math/auto-libm-test-out: Regenerated.
2015-09-24 Steve Ellcey <sellcey@imgtec.com>
* sysdeps/mips/math_private.h (libc_fesetenv_mips): Mark cw as unused.

6
NEWS
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@ -14,9 +14,9 @@ Version 2.23
16985, 17118, 17243, 17244, 17441, 17787, 17886, 17887, 17905, 18084,
18086, 18240, 18265, 18370, 18421, 18480, 18525, 18595, 18610, 18618,
18647, 18661, 18674, 18675, 18681, 18757, 18778, 18781, 18787, 18789,
18790, 18795, 18796, 18820, 18823, 18824, 18857, 18863, 18870, 18872,
18873, 18875, 18887, 18921, 18951, 18952, 18961, 18966, 18967, 18970,
18977, 18980, 18981, 19003.
18790, 18795, 18796, 18803, 18820, 18823, 18824, 18857, 18863, 18870,
18872, 18873, 18875, 18887, 18921, 18951, 18952, 18961, 18966, 18967,
18970, 18977, 18980, 18981, 19003.
* The obsolete header <regexp.h> has been removed. Programs that require
this header must be updated to use <regex.h> instead.

7
math/auto-libm-test-in
View File

@ -1955,6 +1955,13 @@ hypot 0x0.ffffffp-16382 0x0.fp-16383 no-test-inline
hypot 0x0.ffffffp-16382 0x0.fp-16386 no-test-inline
hypot 0 min_subnorm no-test-inline
hypot 0x1p-127 0x1p-149
hypot 0x1p-1023 0x1p-1074
hypot 0x1p-970 0x1p-1074
hypot 0x1p-16383 0x1p-16445 no-test-inline
hypot 0x1p-16384 0x1p-16446 no-test-inline
hypot 0x1p-16383 0x1p-16494 no-test-inline
hypot -0x1.fa7deap+0 0x1.a761bab383ac8p+0
j0 -1.0

1342
math/auto-libm-test-out
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File diff suppressed because it is too large Load Diff

13
sysdeps/i386/fpu/e_hypot.S
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@ -20,8 +20,19 @@
#include <sysdep.h>
#include <i386-math-asm.h>
DEFINE_DBL_MIN
#ifdef PIC
# define MO(op) op##@GOTOFF(%edx)
#else
# define MO(op) op
#endif
.text
ENTRY(__ieee754_hypot)
#ifdef PIC
LOAD_PIC_REG (dx)
#endif
fldl 4(%esp) // x
fxam
fnstsw
@ -38,7 +49,7 @@ ENTRY(__ieee754_hypot)
fmul %st(0) // x * x : y * y
faddp // x * x + y * y
fsqrt
DBL_NARROW_EVAL
DBL_NARROW_EVAL_UFLOW_NONNEG
2: ret
// We have to test whether any of the parameters is Inf.

4
sysdeps/ieee754/dbl-64/e_hypot.c
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@ -149,7 +149,9 @@ __ieee754_hypot (double x, double y)
t1 = 1.0;
GET_HIGH_WORD (high, t1);
SET_HIGH_WORD (t1, high + (k << 20));
return t1 * w;
w *= t1;
math_check_force_underflow_nonneg (w);
return w;
}
else
return w;

4
sysdeps/ieee754/ldbl-128/e_hypotl.c
View File

@ -130,7 +130,9 @@ __ieee754_hypotl(long double x, long double y)
t1 = 1.0L;
GET_LDOUBLE_MSW64(high,t1);
SET_LDOUBLE_MSW64(t1,high+(k<<48));
return t1*w;
w *= t1;
math_check_force_underflow_nonneg (w);
return w;
} else return w;
}
strong_alias (__ieee754_hypotl, __hypotl_finite)

6
sysdeps/ieee754/ldbl-128ibm/e_hypotl.c
View File

@ -125,7 +125,11 @@ __ieee754_hypotl(long double x, long double y)
w = __ieee754_sqrtl(a1*b1-(w*(-w)-(a1*b2+a2*b)));
}
if(k!=0)
return w*kld;
{
w *= kld;
math_check_force_underflow_nonneg (w);
return w;
}
else
return w;
}

4
sysdeps/ieee754/ldbl-96/e_hypotl.c
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@ -132,7 +132,9 @@ long double __ieee754_hypotl(long double x, long double y)
t1 = 1.0;
GET_LDOUBLE_EXP(exp,t1);
SET_LDOUBLE_EXP(t1,exp+k);
return t1*w;
w *= t1;
math_check_force_underflow_nonneg (w);
return w;
} else return w;
}
strong_alias (__ieee754_hypotl, __hypotl_finite)

4
sysdeps/powerpc/fpu/e_hypot.c
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@ -116,7 +116,9 @@ __ieee754_hypot (double x, double y)
{
x *= two1022;
y *= two1022;
return __ieee754_sqrt (x * x + y * y) / two1022;
double ret = __ieee754_sqrt (x * x + y * y) / two1022;
math_check_force_underflow_nonneg (ret);
return ret;
}
else
{