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Fix generic fmax, fmin sNaN handling (bug 20947).

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Various fmax and fmin function implementations mishandle sNaN
arguments:

(a) When both arguments are NaNs, the return value should be a qNaN,
but sometimes it is an sNaN if at least one argument is an sNaN.

(b) Under TS 18661-1 semantics, if either argument is an sNaN then the
result should be a qNaN (whereas if one argument is a qNaN and the
other is not a NaN, the result should be the non-NaN argument).
Various implementations treat sNaNs like qNaNs here.

This patch fixes the generic implementations used in the absence of
architecture-specific versions.

Tested for mips64 and powerpc (together with testcases that I'll add
along with the x86_64 / x86 fixes).

	[BZ #20947]
	* math/s_fmax_template.c (M_DECL_FUNC (__fmax)): Add the arguments
	when either is a signaling NaN.
	* math/s_fmin_template.c (M_DECL_FUNC (__fmin)): Likewise.
This commit is contained in:
Joseph Myers 2016-12-14 22:41:26 +00:00
parent 0acb8a2a85
commit f02bb0004c
3 changed files with 21 additions and 2 deletions
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5
ChangeLog
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@ -1,5 +1,10 @@
2016-12-14 Joseph Myers <joseph@codesourcery.com>
[BZ #20947]
* math/s_fmax_template.c (M_DECL_FUNC (__fmax)): Add the arguments
when either is a signaling NaN.
* math/s_fmin_template.c (M_DECL_FUNC (__fmin)): Likewise.
* bits/long-double.h: New file.
* sysdeps/ieee754/ldbl-128/bits/long-double.h: Likewise.
* sysdeps/ieee754/ldbl-96/bits/long-double.h: Likewise.

9
math/s_fmax_template.c
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@ -22,7 +22,14 @@
FLOAT
M_DECL_FUNC (__fmax) (FLOAT x, FLOAT y)
{
return (isgreaterequal (x, y) || isnan (y)) ? x : y;
if (isgreaterequal (x, y))
return x;
else if (isless (x, y))
return y;
else if (issignaling (x) || issignaling (y))
return x + y;
else
return isnan (y) ? x : y;
}
declare_mgen_alias (__fmax, fmax);

9
math/s_fmin_template.c
View File

@ -23,7 +23,14 @@
FLOAT
M_DECL_FUNC (__fmin) (FLOAT x, FLOAT y)
{
return (islessequal (x, y) || isnan (y)) ? x : y;
if (islessequal (x, y))
return x;
else if (isgreater (x, y))
return y;
else if (issignaling (x) || issignaling (y))
return x + y;
else
return isnan (y) ? x : y;
}
declare_mgen_alias (__fmin, fmin);