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GNU C Library master sources branch master updated. glibc-2.23-414-g8cbd145


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      from  cfac4de69cc70fbd6364e58cf77891a7a30f2e09 (commit)

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- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=8cbd1453ec1c59e54652edcd88256f4023ff77b9

commit 8cbd1453ec1c59e54652edcd88256f4023ff77b9
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Fri Jun 3 21:30:12 2016 +0000

    Fix x86/x86_64 nextafterl incrementing negative subnormals (bug 20205).
    
    The x86 / x86_64 implementation of nextafterl (also used for
    nexttowardl) produces incorrect results (NaNs) when negative
    subnormals, the low 32 bits of whose mantissa are zero, are
    incremented towards zero.  This patch fixes this by disabling the
    logic to decrement the exponent in that case.
    
    Tested for x86_64 and x86.
    
    	[BZ #20205]
    	* sysdeps/i386/fpu/s_nextafterl.c (__nextafterl): Do not adjust
    	exponent when incrementing negative subnormal with low mantissa
    	word zero.
    	* math/libm-test.inc (nextafter_test_data) [TEST_COND_intel96]:
    	Add another test.

diff --git a/ChangeLog b/ChangeLog
index 94a95f3..3e16edf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2016-06-03  Joseph Myers  <joseph@codesourcery.com>
+
+	[BZ #20205]
+	* sysdeps/i386/fpu/s_nextafterl.c (__nextafterl): Do not adjust
+	exponent when incrementing negative subnormal with low mantissa
+	word zero.
+	* math/libm-test.inc (nextafter_test_data) [TEST_COND_intel96]:
+	Add another test.
+
 2016-06-03  Florian Weimer  <fweimer@redhat.com>
 
 	* libio/wstrops.c (_IO_wstr_overflow, enlarge_userbuf): Use
diff --git a/math/libm-test.inc b/math/libm-test.inc
index 8c64c8e..aaa0148 100644
--- a/math/libm-test.inc
+++ b/math/libm-test.inc
@@ -9965,6 +9965,10 @@ static const struct test_ff_f_data nextafter_test_data[] =
     TEST_ff_f (nextafter, -min_subnorm_value, 0, minus_zero, INEXACT_EXCEPTION|UNDERFLOW_EXCEPTION|ERRNO_ERANGE),
     TEST_ff_f (nextafter, -min_subnorm_value, minus_zero, minus_zero, INEXACT_EXCEPTION|UNDERFLOW_EXCEPTION|ERRNO_ERANGE),
 
+#if TEST_COND_intel96
+    TEST_ff_f (nextafter, -0x0.fffffffep-16382L, 0.0L, -0x0.fffffffdfffffffep-16382L, INEXACT_EXCEPTION|UNDERFLOW_EXCEPTION|ERRNO_ERANGE),
+#endif
+
 #if MANT_DIG >= 64
     // XXX Enable once gcc is fixed.
     //TEST_ff_f (nextafter, 0x0.00000040000000000000p-16385L, -0.1L, 0x0.0000003ffffffff00000p-16385L),
diff --git a/sysdeps/i386/fpu/s_nextafterl.c b/sysdeps/i386/fpu/s_nextafterl.c
index 188dc21..600ad7a 100644
--- a/sysdeps/i386/fpu/s_nextafterl.c
+++ b/sysdeps/i386/fpu/s_nextafterl.c
@@ -86,7 +86,7 @@ long double __nextafterl(long double x, long double y)
 	    if(esy>=0||(esx>esy||((esx==esy)&&(hx>hy||((hx==hy)&&(lx>ly)))))){
 	      /* x < y, x -= ulp */
 		if(lx==0) {
-		    if (hx <= 0x80000000) {
+		    if (hx <= 0x80000000 && esx != 0xffff8000) {
 			esx -= 1;
 			hx = hx - 1;
 			if ((esx&0x7fff) > 0)

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

Summary of changes:
 ChangeLog                       |    9 +++++++++
 math/libm-test.inc              |    4 ++++
 sysdeps/i386/fpu/s_nextafterl.c |    2 +-
 3 files changed, 14 insertions(+), 1 deletions(-)


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