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Fix dbl-64 atan in non-default rounding modes (bug 18197).
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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.
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Joseph Myers committed Apr 8, 2015
1 parent d5856d0 commit ae63c7e
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8 changes: 8 additions & 0 deletions ChangeLog
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@@ -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]
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2 changes: 1 addition & 1 deletion NEWS
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Expand Up @@ -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
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2 changes: 2 additions & 0 deletions math/auto-libm-test-in
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Expand Up @@ -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
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50 changes: 50 additions & 0 deletions math/auto-libm-test-out
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Expand Up @@ -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
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2 changes: 2 additions & 0 deletions sysdeps/ieee754/dbl-64/s_atan.c
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Expand Up @@ -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>
Expand Down Expand Up @@ -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)
{
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