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Fix generic fmax, fmin sNaN handling (bug 20947) [committed]
- From: Joseph Myers <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Wed, 14 Dec 2016 22:42:07 +0000
- Subject: Fix generic fmax, fmin sNaN handling (bug 20947) [committed]
- Authentication-results: sourceware.org; auth=none
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). Committed.
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.
diff --git a/math/s_fmax_template.c b/math/s_fmax_template.c
index dea53d4..e855b72 100644
--- a/math/s_fmax_template.c
+++ b/math/s_fmax_template.c
@@ -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);
diff --git a/math/s_fmin_template.c b/math/s_fmin_template.c
index b70989a..82009bb 100644
--- a/math/s_fmin_template.c
+++ b/math/s_fmin_template.c
@@ -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);
--
Joseph S. Myers
joseph@codesourcery.com