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GNU C Library master sources branch master updated. glibc-2.21-349-gfbc68f0

From: jsm28 at sourceware dot org
To: glibc-cvs at sourceware dot org
Date: 15 May 2015 00:16:33 -0000
Subject: GNU C Library master sources branch master updated. glibc-2.21-349-gfbc68f0
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The branch, master has been updated
       via  fbc68f03b0e56db6a07d789fd403eb79d726fe96 (commit)
      from  9a71f1fcf53615c00b5f9e5da4bba92bccb0efb4 (commit)

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- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=fbc68f03b0e56db6a07d789fd403eb79d726fe96

commit fbc68f03b0e56db6a07d789fd403eb79d726fe96
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Fri May 15 00:16:10 2015 +0000

    Fix erfcf spurious underflows (bug 18217).
    
    The flt-32 implementation of erfcf produces spurious underflow
    exceptions for some arguments close to 0, because of calculations
    squaring the argument and then multiplying by small constants.  This
    patch fixes this by adjusting the threshold for arguments for which
    the result is so close to 1 that 1 - x will give the right result from
    2**-56 to 2**-26.  (If 1 - x * 2/sqrt(pi) were used, the errors would be
    on the order of x^3 and a much larger threshold could be used.)
    
    Tested for x86_64 and x86.
    
    	[BZ #18217]
    	* sysdeps/ieee754/flt-32/s_erff.c (__erfcf): Use 2**-26 not 2**-56
    	as threshold for returning 1 - x.
    	* math/auto-libm-test-in: Add more tests of erfc.
    	* math/auto-libm-test-out: Regenerated.

diff --git a/ChangeLog b/ChangeLog
index 1179142..454a8d2 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2015-05-15  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #18217]
+	* sysdeps/ieee754/flt-32/s_erff.c (__erfcf): Use 2**-26 not 2**-56
+	as threshold for returning 1 - x.
+	* math/auto-libm-test-in: Add more tests of erfc.
+	* math/auto-libm-test-out: Regenerated.
+
 2015-05-14  Joseph Myers  <joseph@codesourcery.com>
 
 	[BZ #18196]
diff --git a/NEWS b/NEWS
index c46ee35..9251333 100644
--- a/NEWS
+++ b/NEWS
@@ -16,8 +16,8 @@ Version 2.22
   17964, 17965, 17967, 17969, 17978, 17987, 17991, 17996, 17998, 17999,
   18007, 18019, 18020, 18029, 18030, 18032, 18036, 18038, 18039, 18042,
   18043, 18046, 18047, 18068, 18080, 18093, 18100, 18104, 18110, 18111,
-  18125, 18128, 18138, 18185, 18196, 18197, 18206, 18210, 18211, 18247,
-  18287, 18319, 18333, 18346, 18397, 18409.
+  18125, 18128, 18138, 18185, 18196, 18197, 18206, 18210, 18211, 18217,
+  18247, 18287, 18319, 18333, 18346, 18397, 18409.
 
 * Cache information can be queried via sysconf() function on s390 e.g. with
   _SC_LEVEL1_ICACHE_SIZE as argument.
diff --git a/math/auto-libm-test-in b/math/auto-libm-test-in
index 1deb99a..c4bfe74 100644
--- a/math/auto-libm-test-in
+++ b/math/auto-libm-test-in
@@ -1129,6 +1129,8 @@ erf -0x1.3a0d48p+0
 
 erfc 0.0
 erfc -0
+erfc 0x1p-55
+erfc -0x1p-55
 erfc 0.125
 erfc 0.75
 erfc 1.25
diff --git a/math/auto-libm-test-out b/math/auto-libm-test-out
index 9f6bbbb..d717ea4 100644
--- a/math/auto-libm-test-out
+++ b/math/auto-libm-test-out
@@ -101555,6 +101555,56 @@ erfc -0
 = erfc tonearest ldbl-128ibm -0x0p+0L : 0x1p+0L : inexact-ok
 = erfc towardzero ldbl-128ibm -0x0p+0L : 0x1p+0L : inexact-ok
 = erfc upward ldbl-128ibm -0x0p+0L : 0x1p+0L : inexact-ok
+erfc 0x1p-55
+= erfc downward flt-32 0x2p-56f : 0xf.fffffp-4f : inexact-ok
+= erfc tonearest flt-32 0x2p-56f : 0x1p+0f : inexact-ok
+= erfc towardzero flt-32 0x2p-56f : 0xf.fffffp-4f : inexact-ok
+= erfc upward flt-32 0x2p-56f : 0x1p+0f : inexact-ok
+= erfc downward dbl-64 0x2p-56 : 0xf.ffffffffffff8p-4 : inexact-ok
+= erfc tonearest dbl-64 0x2p-56 : 0x1p+0 : inexact-ok
+= erfc towardzero dbl-64 0x2p-56 : 0xf.ffffffffffff8p-4 : inexact-ok
+= erfc upward dbl-64 0x2p-56 : 0x1p+0 : inexact-ok
+= erfc downward ldbl-96-intel 0x2p-56L : 0xf.ffffffffffffdbep-4L : inexact-ok
+= erfc tonearest ldbl-96-intel 0x2p-56L : 0xf.ffffffffffffdbep-4L : inexact-ok
+= erfc towardzero ldbl-96-intel 0x2p-56L : 0xf.ffffffffffffdbep-4L : inexact-ok
+= erfc upward ldbl-96-intel 0x2p-56L : 0xf.ffffffffffffdbfp-4L : inexact-ok
+= erfc downward ldbl-96-m68k 0x2p-56L : 0xf.ffffffffffffdbep-4L : inexact-ok
+= erfc tonearest ldbl-96-m68k 0x2p-56L : 0xf.ffffffffffffdbep-4L : inexact-ok
+= erfc towardzero ldbl-96-m68k 0x2p-56L : 0xf.ffffffffffffdbep-4L : inexact-ok
+= erfc upward ldbl-96-m68k 0x2p-56L : 0xf.ffffffffffffdbfp-4L : inexact-ok
+= erfc downward ldbl-128 0x2p-56L : 0xf.ffffffffffffdbe4515f7ac925d8p-4L : inexact-ok
+= erfc tonearest ldbl-128 0x2p-56L : 0xf.ffffffffffffdbe4515f7ac925ep-4L : inexact-ok
+= erfc towardzero ldbl-128 0x2p-56L : 0xf.ffffffffffffdbe4515f7ac925d8p-4L : inexact-ok
+= erfc upward ldbl-128 0x2p-56L : 0xf.ffffffffffffdbe4515f7ac925ep-4L : inexact-ok
+= erfc downward ldbl-128ibm 0x2p-56L : 0xf.ffffffffffffdbe4515f7ac924p-4L : inexact-ok
+= erfc tonearest ldbl-128ibm 0x2p-56L : 0xf.ffffffffffffdbe4515f7ac924p-4L : inexact-ok
+= erfc towardzero ldbl-128ibm 0x2p-56L : 0xf.ffffffffffffdbe4515f7ac924p-4L : inexact-ok
+= erfc upward ldbl-128ibm 0x2p-56L : 0xf.ffffffffffffdbe4515f7ac928p-4L : inexact-ok
+erfc -0x1p-55
+= erfc downward flt-32 -0x2p-56f : 0x1p+0f : inexact-ok
+= erfc tonearest flt-32 -0x2p-56f : 0x1p+0f : inexact-ok
+= erfc towardzero flt-32 -0x2p-56f : 0x1p+0f : inexact-ok
+= erfc upward flt-32 -0x2p-56f : 0x1.000002p+0f : inexact-ok
+= erfc downward dbl-64 -0x2p-56 : 0x1p+0 : inexact-ok
+= erfc tonearest dbl-64 -0x2p-56 : 0x1p+0 : inexact-ok
+= erfc towardzero dbl-64 -0x2p-56 : 0x1p+0 : inexact-ok
+= erfc upward dbl-64 -0x2p-56 : 0x1.0000000000001p+0 : inexact-ok
+= erfc downward ldbl-96-intel -0x2p-56L : 0x1.000000000000024p+0L : inexact-ok
+= erfc tonearest ldbl-96-intel -0x2p-56L : 0x1.0000000000000242p+0L : inexact-ok
+= erfc towardzero ldbl-96-intel -0x2p-56L : 0x1.000000000000024p+0L : inexact-ok
+= erfc upward ldbl-96-intel -0x2p-56L : 0x1.0000000000000242p+0L : inexact-ok
+= erfc downward ldbl-96-m68k -0x2p-56L : 0x1.000000000000024p+0L : inexact-ok
+= erfc tonearest ldbl-96-m68k -0x2p-56L : 0x1.0000000000000242p+0L : inexact-ok
+= erfc towardzero ldbl-96-m68k -0x2p-56L : 0x1.000000000000024p+0L : inexact-ok
+= erfc upward ldbl-96-m68k -0x2p-56L : 0x1.0000000000000242p+0L : inexact-ok
+= erfc downward ldbl-128 -0x2p-56L : 0x1.0000000000000241baea08536da2p+0L : inexact-ok
+= erfc tonearest ldbl-128 -0x2p-56L : 0x1.0000000000000241baea08536da2p+0L : inexact-ok
+= erfc towardzero ldbl-128 -0x2p-56L : 0x1.0000000000000241baea08536da2p+0L : inexact-ok
+= erfc upward ldbl-128 -0x2p-56L : 0x1.0000000000000241baea08536da3p+0L : inexact-ok
+= erfc downward ldbl-128ibm -0x2p-56L : 0x1.0000000000000241baea08536d8p+0L : inexact-ok
+= erfc tonearest ldbl-128ibm -0x2p-56L : 0x1.0000000000000241baea08536d8p+0L : inexact-ok
+= erfc towardzero ldbl-128ibm -0x2p-56L : 0x1.0000000000000241baea08536d8p+0L : inexact-ok
+= erfc upward ldbl-128ibm -0x2p-56L : 0x1.0000000000000241baea08536ep+0L : inexact-ok
 erfc 0.125
 = erfc downward flt-32 0x2p-4f : 0xd.c143cp-4f : inexact-ok
 = erfc tonearest flt-32 0x2p-4f : 0xd.c143dp-4f : inexact-ok
diff --git a/sysdeps/ieee754/flt-32/s_erff.c b/sysdeps/ieee754/flt-32/s_erff.c
index d23cff9..2be44cc 100644
--- a/sysdeps/ieee754/flt-32/s_erff.c
+++ b/sysdeps/ieee754/flt-32/s_erff.c
@@ -169,7 +169,7 @@ float __erfcf(float x)
 	}
 
 	if(ix < 0x3f580000) {		/* |x|<0.84375 */
-	    if(ix < 0x23800000)  	/* |x|<2**-56 */
+	    if(ix < 0x32800000)  	/* |x|<2**-26 */
 		return one-x;
 	    z = x*x;
 	    r = pp0+z*(pp1+z*(pp2+z*(pp3+z*pp4)));

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                       |    8 ++++++
 NEWS                            |    4 +-
 math/auto-libm-test-in          |    2 +
 math/auto-libm-test-out         |   50 +++++++++++++++++++++++++++++++++++++++
 sysdeps/ieee754/flt-32/s_erff.c |    2 +-
 5 files changed, 63 insertions(+), 3 deletions(-)


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