Fix dbl-64 atan in non-default rounding modes (bug 18197).

The dbl-64 implementation of atan does computations that expect to run
in round-to-nearest mode, and in other modes the errors can accumulate
to more than the maximum accepted 9ulp.  This patch makes it use
FE_TONEAREST internally, similar to other functions with such issues.

Tested for x86_64 and x86; no ulps updates needed.

	[BZ #18197]
	* sysdeps/ieee754/dbl-64/s_atan.c: Include <fenv.h>.
	(atan): Set FE_TONEAREST mode for internal computations.
	* math/auto-libm-test-in: Add more tests of atan.
	* math/auto-libm-test-out: Regenerated.

diff --git a/ChangeLog b/ChangeLog
index 557871a7f284bb3139490dd09282d5b2eda7df4b..12f264b13ecf6f14a36790197c2dec91c86305e2 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2015-04-08  Joseph Myers  <joseph@codesourcery.com>
+
+       [BZ #18197]
+       * sysdeps/ieee754/dbl-64/s_atan.c: Include <fenv.h>.
+       (atan): Set FE_TONEAREST mode for internal computations.
+       * math/auto-libm-test-in: Add more tests of atan.
+       * math/auto-libm-test-out: Regenerated.
+
 2015-04-07  James Cowgill  <james410@cowgill.org.uk>
 
        [BZ #17930]

diff --git a/NEWS b/NEWS
index d36fed56b2f9f2dd34474297eb34b66f0f120bd6..b6776bcc692c9bc2f149e579294532d88469d52e 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -15,7 +15,7 @@ Version 2.22
   17836, 17912, 17916, 17930, 17932, 17944, 17949, 17964, 17965, 17967,
   17969, 17978, 17987, 17991, 17996, 17998, 17999, 18019, 18020, 18029,
   18030, 18032, 18036, 18038, 18039, 18042, 18043, 18046, 18047, 18068,
-  18080, 18093, 18100, 18104, 18110, 18111, 18128, 18138, 18185.
+  18080, 18093, 18100, 18104, 18110, 18111, 18128, 18138, 18185, 18197.
 
 * A powerpc and powerpc64 optimization for TLS, similar to TLS descriptors
   for LD and GD on x86 and x86-64, has been implemented.  You will need

diff --git a/math/auto-libm-test-in b/math/auto-libm-test-in
index 939f6eaba13533f4c9fcd5dd12020ce5e0aa97f2..d0026d5c0da2ab44cc7d82b55f2629ab24cd6ced 100644 (file)
--- a/math/auto-libm-test-in
+++ b/math/auto-libm-test-in
@@ -240,6 +240,8 @@ atan 1e6
 atan 0x1p-100
 atan 0x1p-600
 atan 0x1p-10000
+atan -0x3.b02d84p-4
+atan -0x3.3fb708p-4
 atan min
 atan -min
 atan min_subnorm

diff --git a/math/auto-libm-test-out b/math/auto-libm-test-out
index 68435abd3595758740be314afc4b9cc24c617c9d..3550f33d9e231fc3b0e91055bfa19a0ef47ff1f3 100644 (file)
--- a/math/auto-libm-test-out
+++ b/math/auto-libm-test-out
@@ -7877,6 +7877,56 @@ atan 0x1p-10000
 = atan tonearest ldbl-128 0x1p-10000L : 0x1p-10000L : inexact-ok
 = atan towardzero ldbl-128 0x1p-10000L : 0xf.fffffffffffffffffffffffffff8p-10004L : inexact-ok
 = atan upward ldbl-128 0x1p-10000L : 0x1p-10000L : inexact-ok
+atan -0x3.b02d84p-4
+= atan downward flt-32 -0x3.b02d84p-4f : -0x3.9ff7e4p-4f : inexact-ok
+= atan tonearest flt-32 -0x3.b02d84p-4f : -0x3.9ff7ep-4f : inexact-ok
+= atan towardzero flt-32 -0x3.b02d84p-4f : -0x3.9ff7ep-4f : inexact-ok
+= atan upward flt-32 -0x3.b02d84p-4f : -0x3.9ff7ep-4f : inexact-ok
+= atan downward dbl-64 -0x3.b02d84p-4 : -0x3.9ff7e1f81370cp-4 : inexact-ok
+= atan tonearest dbl-64 -0x3.b02d84p-4 : -0x3.9ff7e1f81370cp-4 : inexact-ok
+= atan towardzero dbl-64 -0x3.b02d84p-4 : -0x3.9ff7e1f81370ap-4 : inexact-ok
+= atan upward dbl-64 -0x3.b02d84p-4 : -0x3.9ff7e1f81370ap-4 : inexact-ok
+= atan downward ldbl-96-intel -0x3.b02d84p-4L : -0x3.9ff7e1f81370b934p-4L : inexact-ok
+= atan tonearest ldbl-96-intel -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93p-4L : inexact-ok
+= atan towardzero ldbl-96-intel -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93p-4L : inexact-ok
+= atan upward ldbl-96-intel -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93p-4L : inexact-ok
+= atan downward ldbl-96-m68k -0x3.b02d84p-4L : -0x3.9ff7e1f81370b934p-4L : inexact-ok
+= atan tonearest ldbl-96-m68k -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93p-4L : inexact-ok
+= atan towardzero ldbl-96-m68k -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93p-4L : inexact-ok
+= atan upward ldbl-96-m68k -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93p-4L : inexact-ok
+= atan downward ldbl-128 -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93195e0357d0b5ap-4L : inexact-ok
+= atan tonearest ldbl-128 -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93195e0357d0b5ap-4L : inexact-ok
+= atan towardzero ldbl-128 -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93195e0357d0b58p-4L : inexact-ok
+= atan upward ldbl-128 -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93195e0357d0b58p-4L : inexact-ok
+= atan downward ldbl-128ibm -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93195e0357d0cp-4L : inexact-ok
+= atan tonearest ldbl-128ibm -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93195e0357d0bp-4L : inexact-ok
+= atan towardzero ldbl-128ibm -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93195e0357d0bp-4L : inexact-ok
+= atan upward ldbl-128ibm -0x3.b02d84p-4L : -0x3.9ff7e1f81370b93195e0357d0bp-4L : inexact-ok
+atan -0x3.3fb708p-4
+= atan downward flt-32 -0x3.3fb708p-4f : -0x3.348f0cp-4f : inexact-ok
+= atan tonearest flt-32 -0x3.3fb708p-4f : -0x3.348f08p-4f : inexact-ok
+= atan towardzero flt-32 -0x3.3fb708p-4f : -0x3.348f08p-4f : inexact-ok
+= atan upward flt-32 -0x3.3fb708p-4f : -0x3.348f08p-4f : inexact-ok
+= atan downward dbl-64 -0x3.3fb708p-4 : -0x3.348f092072332p-4 : inexact-ok
+= atan tonearest dbl-64 -0x3.3fb708p-4 : -0x3.348f092072332p-4 : inexact-ok
+= atan towardzero dbl-64 -0x3.3fb708p-4 : -0x3.348f09207233p-4 : inexact-ok
+= atan upward dbl-64 -0x3.3fb708p-4 : -0x3.348f09207233p-4 : inexact-ok
+= atan downward ldbl-96-intel -0x3.3fb708p-4L : -0x3.348f092072331fdcp-4L : inexact-ok
+= atan tonearest ldbl-96-intel -0x3.3fb708p-4L : -0x3.348f092072331fd8p-4L : inexact-ok
+= atan towardzero ldbl-96-intel -0x3.3fb708p-4L : -0x3.348f092072331fd8p-4L : inexact-ok
+= atan upward ldbl-96-intel -0x3.3fb708p-4L : -0x3.348f092072331fd8p-4L : inexact-ok
+= atan downward ldbl-96-m68k -0x3.3fb708p-4L : -0x3.348f092072331fdcp-4L : inexact-ok
+= atan tonearest ldbl-96-m68k -0x3.3fb708p-4L : -0x3.348f092072331fd8p-4L : inexact-ok
+= atan towardzero ldbl-96-m68k -0x3.3fb708p-4L : -0x3.348f092072331fd8p-4L : inexact-ok
+= atan upward ldbl-96-m68k -0x3.3fb708p-4L : -0x3.348f092072331fd8p-4L : inexact-ok
+= atan downward ldbl-128 -0x3.3fb708p-4L : -0x3.348f092072331fd8ca0cbff348d8p-4L : inexact-ok
+= atan tonearest ldbl-128 -0x3.3fb708p-4L : -0x3.348f092072331fd8ca0cbff348d6p-4L : inexact-ok
+= atan towardzero ldbl-128 -0x3.3fb708p-4L : -0x3.348f092072331fd8ca0cbff348d6p-4L : inexact-ok
+= atan upward ldbl-128 -0x3.3fb708p-4L : -0x3.348f092072331fd8ca0cbff348d6p-4L : inexact-ok
+= atan downward ldbl-128ibm -0x3.3fb708p-4L : -0x3.348f092072331fd8ca0cbff349p-4L : inexact-ok
+= atan tonearest ldbl-128ibm -0x3.3fb708p-4L : -0x3.348f092072331fd8ca0cbff349p-4L : inexact-ok
+= atan towardzero ldbl-128ibm -0x3.3fb708p-4L : -0x3.348f092072331fd8ca0cbff348p-4L : inexact-ok
+= atan upward ldbl-128ibm -0x3.3fb708p-4L : -0x3.348f092072331fd8ca0cbff348p-4L : inexact-ok
 atan min
 = atan downward flt-32 0x4p-128f : 0x3.fffff8p-128f : inexact-ok underflow-ok errno-erange-ok
 = atan tonearest flt-32 0x4p-128f : 0x4p-128f : inexact-ok underflow-ok errno-erange-ok

diff --git a/sysdeps/ieee754/dbl-64/s_atan.c b/sysdeps/ieee754/dbl-64/s_atan.c
index 7b598f14a9f6b6c6357116c5d1c6e4ded8e37b85..5035ae87bc8a2c2404ef4cf0e5a57aed62db286a 100644 (file)
--- a/sysdeps/ieee754/dbl-64/s_atan.c
+++ b/sysdeps/ieee754/dbl-64/s_atan.c
@@ -41,6 +41,7 @@
 #include "MathLib.h"
 #include "uatan.tbl"
 #include "atnat.h"
+#include <fenv.h>
 #include <float.h>
 #include <math.h>
 #include <math_private.h>
@@ -81,6 +82,7 @@ atan (double x)
     return x + x;
 
   /* Regular values of x, including denormals +-0 and +-INF */
+  SET_RESTORE_ROUND (FE_TONEAREST);
   u = (x < 0) ? -x : x;
   if (u < C)
     {