Handle more state in i386/x86_64 fesetenv (bug 16068).

fenv_t should include architecture-specific floating-point modes and
status flags.  i386 and x86_64 fesetenv limit which bits they use from
the x87 status and control words, when using saved state, and limit
which parts of the state they set to fixed values, when using
FE_DFL_ENV / FE_NOMASK_ENV.  The following should be included but are
excluded in at least some cases: status and masking for the "denormal
operand" exception (which isn't part of FE_ALL_EXCEPT); precision
control (explicitly mentioned in Annex F as something that counts as
part of the floating-point environment); MXCSR FZ and DAZ bits (for
FE_DFL_ENV and FE_NOMASK_ENV).  This patch arranges for this extra
state to be handled by fesetenv (and thereby by feupdateenv, which
calls fesetenv).

(Note that glibc functions using floating point are not generally
expected to work correctly with non-default values of this state,
especially precision control, but it is still logically part of the
floating-point environment and should be handled as such by fesetenv.
Changes to the state relating to subnormals ought generally to work
with libm functions when the arguments aren't subnormal and neither
are the expected results; that's a consequence of functions avoiding
spurious internal underflows.)

A question arising from this is whether FE_NOMASK_ENV should or should
not mask the "denormal operand" exception.  I decided it should mask
that exception.  This is the status quo - previously that exception
could only be unmasked by direct manipulation of control registers
(possibly via <fpu_control.h>).  In addition, it means that use of
FE_NOMASK_ENV leaves a floating-point environment the same as could be
obtained by fesetenv (FE_DFL_ENV); feenableexcept (FE_ALL_EXCEPT);,
rather than an environment in which an exception is unmasked that
could only be masked again by using fesetenv with FE_DFL_ENV (or a
previously saved environment) - this exception not being usable with
other <fenv.h> functions because it's outside FE_ALL_EXCEPT.

Tested for x86_64 and x86.

	[BZ #16068]
	* sysdeps/i386/fpu/fesetenv.c: Include <fpu_control.h>.
	(FE_ALL_EXCEPT_X86): New macro.
	(__fesetenv): Use FE_ALL_EXCEPT_X86 in most places instead of
	FE_ALL_EXCEPT.  Ensure precision control is included in
	floating-point state.  Ensure that FE_DFL_ENV and FE_NOMASK_ENV
	handle "denormal operand exception" and clear FZ and DAZ bits.
	* sysdeps/x86_64/fpu/fesetenv.c: Include <fpu_control.h>.
	(FE_ALL_EXCEPT_X86): New macro.
	(__fesetenv): Use FE_ALL_EXCEPT_X86 in most places instead of
	FE_ALL_EXCEPT.  Ensure precision control is included in
	floating-point state.  Ensure that FE_DFL_ENV and FE_NOMASK_ENV
	handle "denormal operand exception" and clear FZ and DAZ bits.
	* sysdeps/x86/fpu/test-fenv-sse-2.c: New file.
	* sysdeps/x86/fpu/test-fenv-x87.c: Likewise.
	* sysdeps/x86/fpu/Makefile [$(subdir) = math] (tests): Add
	test-fenv-x87 and test-fenv-sse-2.
	[$(subdir) = math] (CFLAGS-test-fenv-sse-2.c): New variable.

7 files changed, 438 insertions, 33 deletions

diff --git a/ChangeLog b/ChangeLog
index 52cd9f3977..9ef00a7a32 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,24 @@
 2015-10-28  Joseph Myers  <joseph@codesourcery.com>
 
+	[BZ #16068]
+	* sysdeps/i386/fpu/fesetenv.c: Include <fpu_control.h>.
+	(FE_ALL_EXCEPT_X86): New macro.
+	(__fesetenv): Use FE_ALL_EXCEPT_X86 in most places instead of
+	FE_ALL_EXCEPT.  Ensure precision control is included in
+	floating-point state.  Ensure that FE_DFL_ENV and FE_NOMASK_ENV
+	handle "denormal operand exception" and clear FZ and DAZ bits.
+	* sysdeps/x86_64/fpu/fesetenv.c: Include <fpu_control.h>.
+	(FE_ALL_EXCEPT_X86): New macro.
+	(__fesetenv): Use FE_ALL_EXCEPT_X86 in most places instead of
+	FE_ALL_EXCEPT.  Ensure precision control is included in
+	floating-point state.  Ensure that FE_DFL_ENV and FE_NOMASK_ENV
+	handle "denormal operand exception" and clear FZ and DAZ bits.
+	* sysdeps/x86/fpu/test-fenv-sse-2.c: New file.
+	* sysdeps/x86/fpu/test-fenv-x87.c: Likewise.
+	* sysdeps/x86/fpu/Makefile [$(subdir) = math] (tests): Add
+	test-fenv-x87 and test-fenv-sse-2.
+	[$(subdir) = math] (CFLAGS-test-fenv-sse-2.c): New variable.
+
 	* math/libm-test.inc (BUILD_COMPLEX): Remove macro.
 	* math/test-double.h (BUILD_COMPLEX): New macro.
 	* math/test-float.h (BUILD_COMPLEX): Likewise.
diff --git a/NEWS b/NEWS
index 9b343917f5..0831d35881 100644
--- a/NEWS
+++ b/NEWS
@@ -10,18 +10,18 @@ Version 2.23
 * The following bugs are resolved with this release:
 
   887, 2542, 2543, 2558, 2898, 4404, 6803, 10432, 14341, 14912, 15367,
-  15384, 15470, 15491, 15786, 15918, 16141, 16296, 16347, 16399, 16415,
-  16422, 16517, 16519, 16520, 16521, 16620, 16734, 16973, 16985, 17118,
-  17243, 17244, 17250, 17404, 17441, 17787, 17886, 17887, 17905, 18084,
-  18086, 18240, 18265, 18370, 18421, 18480, 18525, 18595, 18589, 18610,
-  18611, 18618, 18647, 18661, 18674, 18675, 18681, 18699, 18724, 18743,
-  18757, 18778, 18781, 18787, 18789, 18790, 18795, 18796, 18803, 18820,
-  18823, 18824, 18825, 18857, 18863, 18870, 18872, 18873, 18875, 18887,
-  18918, 18921, 18928, 18951, 18952, 18953, 18956, 18961, 18966, 18967,
-  18969, 18970, 18977, 18980, 18981, 18982, 18985, 19003, 19007, 19012,
-  19016, 19018, 19032, 19046, 19048, 19049, 19050, 19059, 19071, 19074,
-  19076, 19077, 19078, 19079, 19085, 19086, 19088, 19094, 19095, 19124,
-  19125, 19129, 19134, 19137, 19156, 19174, 19181.
+  15384, 15470, 15491, 15786, 15918, 16068, 16141, 16296, 16347, 16399,
+  16415, 16422, 16517, 16519, 16520, 16521, 16620, 16734, 16973, 16985,
+  17118, 17243, 17244, 17250, 17404, 17441, 17787, 17886, 17887, 17905,
+  18084, 18086, 18240, 18265, 18370, 18421, 18480, 18525, 18595, 18589,
+  18610, 18611, 18618, 18647, 18661, 18674, 18675, 18681, 18699, 18724,
+  18743, 18757, 18778, 18781, 18787, 18789, 18790, 18795, 18796, 18803,
+  18820, 18823, 18824, 18825, 18857, 18863, 18870, 18872, 18873, 18875,
+  18887, 18918, 18921, 18928, 18951, 18952, 18953, 18956, 18961, 18966,
+  18967, 18969, 18970, 18977, 18980, 18981, 18982, 18985, 19003, 19007,
+  19012, 19016, 19018, 19032, 19046, 19048, 19049, 19050, 19059, 19071,
+  19074, 19076, 19077, 19078, 19079, 19085, 19086, 19088, 19094, 19095,
+  19124, 19125, 19129, 19134, 19137, 19156, 19174, 19181.
 
 * A defect in the malloc implementation, present since glibc 2.15 (2012) or
   glibc 2.10 via --enable-experimental-malloc (2009), could result in the
diff --git a/sysdeps/i386/fpu/fesetenv.c b/sysdeps/i386/fpu/fesetenv.c
index 910aa0991c..f3b9cefee5 100644
--- a/sysdeps/i386/fpu/fesetenv.c
+++ b/sysdeps/i386/fpu/fesetenv.c
@@ -18,12 +18,18 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <fenv.h>
+#include <fpu_control.h>
 #include <assert.h>
 #include <unistd.h>
 #include <ldsodefs.h>
 #include <dl-procinfo.h>
 
 
+/* All exceptions, including the x86-specific "denormal operand"
+   exception.  */
+#define FE_ALL_EXCEPT_X86 (FE_ALL_EXCEPT | __FE_DENORM)
+
+
 int
 __fesetenv (const fenv_t *envp)
 {
@@ -40,22 +46,30 @@ __fesetenv (const fenv_t *envp)
 
   if (envp == FE_DFL_ENV)
     {
-      temp.__control_word |= FE_ALL_EXCEPT;
+      temp.__control_word |= FE_ALL_EXCEPT_X86;
       temp.__control_word &= ~FE_TOWARDZERO;
-      temp.__status_word &= ~FE_ALL_EXCEPT;
+      temp.__control_word |= _FPU_EXTENDED;
+      temp.__status_word &= ~FE_ALL_EXCEPT_X86;
     }
   else if (envp == FE_NOMASK_ENV)
     {
       temp.__control_word &= ~(FE_ALL_EXCEPT | FE_TOWARDZERO);
-      temp.__status_word &= ~FE_ALL_EXCEPT;
+      /* Keep the "denormal operand" exception masked.  */
+      temp.__control_word |= __FE_DENORM;
+      temp.__control_word |= _FPU_EXTENDED;
+      temp.__status_word &= ~FE_ALL_EXCEPT_X86;
     }
   else
     {
-      temp.__control_word &= ~(FE_ALL_EXCEPT | FE_TOWARDZERO);
+      temp.__control_word &= ~(FE_ALL_EXCEPT_X86
+			       | FE_TOWARDZERO
+			       | _FPU_EXTENDED);
       temp.__control_word |= (envp->__control_word
-			      & (FE_ALL_EXCEPT | FE_TOWARDZERO));
-      temp.__status_word &= ~FE_ALL_EXCEPT;
-      temp.__status_word |= envp->__status_word & FE_ALL_EXCEPT;
+			      & (FE_ALL_EXCEPT_X86
+				 | FE_TOWARDZERO
+				 | _FPU_EXTENDED));
+      temp.__status_word &= ~FE_ALL_EXCEPT_X86;
+      temp.__status_word |= envp->__status_word & FE_ALL_EXCEPT_X86;
     }
   temp.__eip = 0;
   temp.__cs_selector = 0;
@@ -73,22 +87,28 @@ __fesetenv (const fenv_t *envp)
       if (envp == FE_DFL_ENV)
 	{
 	  /* Clear SSE exceptions.  */
-	  mxcsr &= ~FE_ALL_EXCEPT;
+	  mxcsr &= ~FE_ALL_EXCEPT_X86;
 	  /* Set mask for SSE MXCSR.  */
-	  mxcsr |= (FE_ALL_EXCEPT << 7);
+	  mxcsr |= (FE_ALL_EXCEPT_X86 << 7);
 	  /* Set rounding to FE_TONEAREST.  */
 	  mxcsr &= ~0x6000;
 	  mxcsr |= (FE_TONEAREST << 3);
+	  /* Clear the FZ and DAZ bits.  */
+	  mxcsr &= ~0x8040;
 	}
       else if (envp == FE_NOMASK_ENV)
 	{
 	  /* Clear SSE exceptions.  */
-	  mxcsr &= ~FE_ALL_EXCEPT;
+	  mxcsr &= ~FE_ALL_EXCEPT_X86;
 	  /* Do not mask exceptions.  */
 	  mxcsr &= ~(FE_ALL_EXCEPT << 7);
+	  /* Keep the "denormal operand" exception masked.  */
+	  mxcsr |= (__FE_DENORM << 7);
 	  /* Set rounding to FE_TONEAREST.  */
 	  mxcsr &= ~0x6000;
 	  mxcsr |= (FE_TONEAREST << 3);
+	  /* Clear the FZ and DAZ bits.  */
+	  mxcsr &= ~0x8040;
 	}
       else
 	mxcsr = envp->__eip;
diff --git a/sysdeps/x86/fpu/Makefile b/sysdeps/x86/fpu/Makefile
index d38497cff3..b561995658 100644
--- a/sysdeps/x86/fpu/Makefile
+++ b/sysdeps/x86/fpu/Makefile
@@ -1,6 +1,7 @@
 ifeq ($(subdir),math)
 libm-support += powl_helper
-tests += test-fenv-sse test-fenv-clear-sse
+tests += test-fenv-sse test-fenv-clear-sse test-fenv-x87 test-fenv-sse-2
 CFLAGS-test-fenv-sse.c += -msse2 -mfpmath=sse
 CFLAGS-test-fenv-clear-sse.c += -msse2 -mfpmath=sse
+CFLAGS-test-fenv-sse-2.c += -msse2 -mfpmath=sse
 endif
diff --git a/sysdeps/x86/fpu/test-fenv-sse-2.c b/sysdeps/x86/fpu/test-fenv-sse-2.c
new file mode 100644
index 0000000000..12946e63ce
--- /dev/null
+++ b/sysdeps/x86/fpu/test-fenv-sse-2.c
@@ -0,0 +1,176 @@
+/* Test x86-specific floating-point environment (bug 16068): SSE part.
+   Copyright (C) 2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <cpuid.h>
+#include <fenv.h>
+#include <float.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+
+static bool
+have_sse2 (void)
+{
+  unsigned int eax, ebx, ecx, edx;
+
+  if (!__get_cpuid (1, &eax, &ebx, &ecx, &edx))
+    return false;
+
+  return (edx & bit_SSE2) != 0;
+}
+
+static uint32_t
+get_sse_mxcsr (void)
+{
+  uint32_t temp;
+  __asm__ __volatile__ ("stmxcsr %0" : "=m" (temp));
+  return temp;
+}
+
+static void
+set_sse_mxcsr (uint32_t val)
+{
+  __asm__ __volatile__ ("ldmxcsr %0" : : "m" (val));
+}
+
+static void
+set_sse_mxcsr_bits (uint32_t mask, uint32_t bits)
+{
+  uint32_t mxcsr = get_sse_mxcsr ();
+  mxcsr = (mxcsr & ~mask) | bits;
+  set_sse_mxcsr (mxcsr);
+}
+
+static int
+test_sse_mxcsr_bits (const char *test, uint32_t mask, uint32_t bits)
+{
+  uint32_t mxcsr = get_sse_mxcsr ();
+  printf ("Testing %s: mxcsr = %x\n", test, mxcsr);
+  if ((mxcsr & mask) == bits)
+    {
+      printf ("PASS: %s\n", test);
+      return 0;
+    }
+  else
+    {
+      printf ("FAIL: %s\n", test);
+      return 1;
+    }
+}
+
+#define MXCSR_FZ 0x8000
+#define MXCSR_DAZ 0x40
+#define MXCSR_DE 0x2
+#define MXCSR_DM 0x100
+
+static __attribute__ ((noinline)) int
+sse_tests (void)
+{
+  int result = 0;
+  fenv_t env1, env2;
+  /* Test FZ bit.  */
+  fegetenv (&env1);
+  set_sse_mxcsr_bits (MXCSR_FZ, MXCSR_FZ);
+  fegetenv (&env2);
+  fesetenv (&env1);
+  result |= test_sse_mxcsr_bits ("fesetenv FZ restoration",
+				 MXCSR_FZ, 0);
+  set_sse_mxcsr_bits (MXCSR_FZ, 0);
+  fesetenv (&env2);
+  result |= test_sse_mxcsr_bits ("fesetenv FZ restoration 2",
+				 MXCSR_FZ, MXCSR_FZ);
+  set_sse_mxcsr_bits (MXCSR_FZ, MXCSR_FZ);
+  fesetenv (FE_NOMASK_ENV);
+  result |= test_sse_mxcsr_bits ("fesetenv (FE_NOMASK_ENV) FZ restoration",
+				 MXCSR_FZ, 0);
+  set_sse_mxcsr_bits (MXCSR_FZ, MXCSR_FZ);
+  fesetenv (FE_DFL_ENV);
+  result |= test_sse_mxcsr_bits ("fesetenv (FE_DFL_ENV) FZ restoration",
+				 MXCSR_FZ, 0);
+  /* Test DAZ bit.  */
+  set_sse_mxcsr_bits (MXCSR_DAZ, MXCSR_DAZ);
+  fegetenv (&env2);
+  fesetenv (&env1);
+  result |= test_sse_mxcsr_bits ("fesetenv DAZ restoration",
+				 MXCSR_DAZ, 0);
+  set_sse_mxcsr_bits (MXCSR_DAZ, 0);
+  fesetenv (&env2);
+  result |= test_sse_mxcsr_bits ("fesetenv DAZ restoration 2",
+				 MXCSR_DAZ, MXCSR_DAZ);
+  set_sse_mxcsr_bits (MXCSR_DAZ, MXCSR_DAZ);
+  fesetenv (FE_NOMASK_ENV);
+  result |= test_sse_mxcsr_bits ("fesetenv (FE_NOMASK_ENV) DAZ restoration",
+				 MXCSR_DAZ, 0);
+  set_sse_mxcsr_bits (MXCSR_DAZ, MXCSR_DAZ);
+  fesetenv (FE_DFL_ENV);
+  result |= test_sse_mxcsr_bits ("fesetenv (FE_DFL_ENV) DAZ restoration",
+				 MXCSR_DAZ, 0);
+  /* Test DM bit.  */
+  set_sse_mxcsr_bits (MXCSR_DM, 0);
+  fegetenv (&env2);
+  fesetenv (&env1);
+  result |= test_sse_mxcsr_bits ("fesetenv DM restoration",
+				 MXCSR_DM, MXCSR_DM);
+  set_sse_mxcsr_bits (MXCSR_DM, MXCSR_DM);
+  fesetenv (&env2);
+  result |= test_sse_mxcsr_bits ("fesetenv DM restoration 2",
+				 MXCSR_DM, 0);
+  set_sse_mxcsr_bits (MXCSR_DM, 0);
+  /* Presume FE_NOMASK_ENV should leave the "denormal operand"
+     exception masked, as not a standard exception.  */
+  fesetenv (FE_NOMASK_ENV);
+  result |= test_sse_mxcsr_bits ("fesetenv (FE_NOMASK_ENV) DM restoration",
+				 MXCSR_DM, MXCSR_DM);
+  set_sse_mxcsr_bits (MXCSR_DM, 0);
+  fesetenv (FE_DFL_ENV);
+  result |= test_sse_mxcsr_bits ("fesetenv (FE_DFL_ENV) DM restoration",
+				 MXCSR_DM, MXCSR_DM);
+  /* Test DE bit.  */
+  set_sse_mxcsr_bits (MXCSR_DE, MXCSR_DE);
+  fegetenv (&env2);
+  fesetenv (&env1);
+  result |= test_sse_mxcsr_bits ("fesetenv DE restoration",
+				 MXCSR_DE, 0);
+  set_sse_mxcsr_bits (MXCSR_DE, 0);
+  fesetenv (&env2);
+  result |= test_sse_mxcsr_bits ("fesetenv DE restoration 2",
+				 MXCSR_DE, MXCSR_DE);
+  set_sse_mxcsr_bits (MXCSR_DE, MXCSR_DE);
+  fesetenv (FE_NOMASK_ENV);
+  result |= test_sse_mxcsr_bits ("fesetenv (FE_NOMASK_ENV) DE restoration",
+				 MXCSR_DE, 0);
+  set_sse_mxcsr_bits (MXCSR_DE, MXCSR_DE);
+  fesetenv (FE_DFL_ENV);
+  result |= test_sse_mxcsr_bits ("fesetenv (FE_DFL_ENV) DE restoration",
+				 MXCSR_DE, 0);
+  return result;
+}
+
+static int
+do_test (void)
+{
+  if (!have_sse2 ())
+    {
+      puts ("CPU does not support SSE2, cannot test");
+      return 0;
+    }
+  return sse_tests ();
+}
+
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>
diff --git a/sysdeps/x86/fpu/test-fenv-x87.c b/sysdeps/x86/fpu/test-fenv-x87.c
new file mode 100644
index 0000000000..2f74471eac
--- /dev/null
+++ b/sysdeps/x86/fpu/test-fenv-x87.c
@@ -0,0 +1,169 @@
+/* Test x86-specific floating-point environment (bug 16068): x87 part.
+   Copyright (C) 2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <fenv.h>
+#include <float.h>
+#include <fpu_control.h>
+#include <stdint.h>
+#include <stdio.h>
+
+static uint16_t
+get_x87_cw (void)
+{
+  fpu_control_t cw;
+  _FPU_GETCW (cw);
+  return cw;
+}
+
+static void
+set_x87_cw (uint16_t val)
+{
+  fpu_control_t cw = val;
+  _FPU_SETCW (cw);
+}
+
+static void
+set_x87_cw_bits (uint16_t mask, uint16_t bits)
+{
+  uint16_t cw = get_x87_cw ();
+  cw = (cw & ~mask) | bits;
+  set_x87_cw (cw);
+}
+
+static int
+test_x87_cw_bits (const char *test, uint16_t mask, uint16_t bits)
+{
+  uint16_t cw = get_x87_cw ();
+  printf ("Testing %s: cw = %x\n", test, cw);
+  if ((cw & mask) == bits)
+    {
+      printf ("PASS: %s\n", test);
+      return 0;
+    }
+  else
+    {
+      printf ("FAIL: %s\n", test);
+      return 1;
+    }
+}
+
+static uint16_t
+get_x87_sw (void)
+{
+  uint16_t temp;
+  __asm__ __volatile__ ("fnstsw %0" : "=a" (temp));
+  return temp;
+}
+
+static void
+set_x87_sw_bits (uint16_t mask, uint16_t bits)
+{
+  fenv_t temp;
+  __asm__ __volatile__ ("fnstenv %0" : "=m" (temp));
+  temp.__status_word = (temp.__status_word & ~mask) | bits;
+  __asm__ __volatile__ ("fldenv %0" : : "m" (temp));
+}
+
+static int
+test_x87_sw_bits (const char *test, uint16_t mask, uint16_t bits)
+{
+  uint16_t sw = get_x87_sw ();
+  printf ("Testing %s: sw = %x\n", test, sw);
+  if ((sw & mask) == bits)
+    {
+      printf ("PASS: %s\n", test);
+      return 0;
+    }
+  else
+    {
+      printf ("FAIL: %s\n", test);
+      return 1;
+    }
+}
+
+#define X87_CW_PREC_MASK _FPU_EXTENDED
+
+static int
+do_test (void)
+{
+  int result = 0;
+  fenv_t env1, env2;
+  /* Test precision mask.  */
+  fegetenv (&env1);
+  set_x87_cw_bits (X87_CW_PREC_MASK, _FPU_SINGLE);
+  fegetenv (&env2);
+  fesetenv (&env1);
+  result |= test_x87_cw_bits ("fesetenv precision restoration",
+			      X87_CW_PREC_MASK, _FPU_EXTENDED);
+  set_x87_cw_bits (X87_CW_PREC_MASK, _FPU_EXTENDED);
+  fesetenv (&env2);
+  result |= test_x87_cw_bits ("fesetenv precision restoration 2",
+			      X87_CW_PREC_MASK, _FPU_SINGLE);
+  set_x87_cw_bits (X87_CW_PREC_MASK, _FPU_DOUBLE);
+  fesetenv (FE_NOMASK_ENV);
+  result |= test_x87_cw_bits ("fesetenv (FE_NOMASK_ENV) precision restoration",
+			      X87_CW_PREC_MASK, _FPU_EXTENDED);
+  set_x87_cw_bits (X87_CW_PREC_MASK, _FPU_SINGLE);
+  fesetenv (FE_DFL_ENV);
+  result |= test_x87_cw_bits ("fesetenv (FE_DFL_ENV) precision restoration",
+			      X87_CW_PREC_MASK, _FPU_EXTENDED);
+  /* Test x87 denormal operand masking.  */
+  set_x87_cw_bits (_FPU_MASK_DM, 0);
+  fegetenv (&env2);
+  fesetenv (&env1);
+  result |= test_x87_cw_bits ("fesetenv denormal mask restoration",
+			      _FPU_MASK_DM, _FPU_MASK_DM);
+  set_x87_cw_bits (_FPU_MASK_DM, _FPU_MASK_DM);
+  fesetenv (&env2);
+  result |= test_x87_cw_bits ("fesetenv denormal mask restoration 2",
+			      _FPU_MASK_DM, 0);
+  set_x87_cw_bits (_FPU_MASK_DM, 0);
+  /* Presume FE_NOMASK_ENV should leave the "denormal operand"
+     exception masked, as not a standard exception.  */
+  fesetenv (FE_NOMASK_ENV);
+  result |= test_x87_cw_bits ("fesetenv (FE_NOMASK_ENV) denormal mask "
+			      "restoration",
+			      _FPU_MASK_DM, _FPU_MASK_DM);
+  set_x87_cw_bits (_FPU_MASK_DM, 0);
+  fesetenv (FE_DFL_ENV);
+  result |= test_x87_cw_bits ("fesetenv (FE_DFL_ENV) denormal mask "
+			      "restoration",
+			      _FPU_MASK_DM, _FPU_MASK_DM);
+  /* Test x87 denormal operand exception.  */
+  set_x87_sw_bits (__FE_DENORM, __FE_DENORM);
+  fegetenv (&env2);
+  fesetenv (&env1);
+  result |= test_x87_sw_bits ("fesetenv denormal exception restoration",
+			      __FE_DENORM, 0);
+  set_x87_sw_bits (__FE_DENORM, 0);
+  fesetenv (&env2);
+  result |= test_x87_sw_bits ("fesetenv denormal exception restoration 2",
+			      __FE_DENORM, __FE_DENORM);
+  set_x87_sw_bits (__FE_DENORM, __FE_DENORM);
+  fesetenv (FE_NOMASK_ENV);
+  result |= test_x87_sw_bits ("fesetenv (FE_NOMASK_ENV) exception restoration",
+			      __FE_DENORM, 0);
+  set_x87_sw_bits (__FE_DENORM, __FE_DENORM);
+  fesetenv (FE_DFL_ENV);
+  result |= test_x87_sw_bits ("fesetenv (FE_DFL_ENV) exception restoration",
+			      __FE_DENORM, 0);
+  return result;
+}
+
+#define TEST_FUNCTION do_test ()
+#include <test-skeleton.c>
diff --git a/sysdeps/x86_64/fpu/fesetenv.c b/sysdeps/x86_64/fpu/fesetenv.c
index 9950aa734a..381540f687 100644
--- a/sysdeps/x86_64/fpu/fesetenv.c
+++ b/sysdeps/x86_64/fpu/fesetenv.c
@@ -17,9 +17,15 @@
    <http://www.gnu.org/licenses/>.  */
 
 #include <fenv.h>
+#include <fpu_control.h>
 #include <assert.h>
 
 
+/* All exceptions, including the x86-specific "denormal operand"
+   exception.  */
+#define FE_ALL_EXCEPT_X86 (FE_ALL_EXCEPT | __FE_DENORM)
+
+
 int
 __fesetenv (const fenv_t *envp)
 {
@@ -34,47 +40,61 @@ __fesetenv (const fenv_t *envp)
 
   if (envp == FE_DFL_ENV)
     {
-      temp.__control_word |= FE_ALL_EXCEPT;
+      temp.__control_word |= FE_ALL_EXCEPT_X86;
       temp.__control_word &= ~FE_TOWARDZERO;
-      temp.__status_word &= ~FE_ALL_EXCEPT;
+      temp.__control_word |= _FPU_EXTENDED;
+      temp.__status_word &= ~FE_ALL_EXCEPT_X86;
       temp.__eip = 0;
       temp.__cs_selector = 0;
       temp.__opcode = 0;
       temp.__data_offset = 0;
       temp.__data_selector = 0;
       /* Clear SSE exceptions.  */
-      temp.__mxcsr &= ~FE_ALL_EXCEPT;
+      temp.__mxcsr &= ~FE_ALL_EXCEPT_X86;
       /* Set mask for SSE MXCSR.  */
-      temp.__mxcsr |= (FE_ALL_EXCEPT << 7);
+      temp.__mxcsr |= (FE_ALL_EXCEPT_X86 << 7);
       /* Set rounding to FE_TONEAREST.  */
       temp.__mxcsr &= ~ 0x6000;
       temp.__mxcsr |= (FE_TONEAREST << 3);
+      /* Clear the FZ and DAZ bits.  */
+      temp.__mxcsr &= ~0x8040;
     }
   else if (envp == FE_NOMASK_ENV)
     {
       temp.__control_word &= ~(FE_ALL_EXCEPT | FE_TOWARDZERO);
-      temp.__status_word &= ~FE_ALL_EXCEPT;
+      /* Keep the "denormal operand" exception masked.  */
+      temp.__control_word |= __FE_DENORM;
+      temp.__control_word |= _FPU_EXTENDED;
+      temp.__status_word &= ~FE_ALL_EXCEPT_X86;
       temp.__eip = 0;
       temp.__cs_selector = 0;
       temp.__opcode = 0;
       temp.__data_offset = 0;
       temp.__data_selector = 0;
       /* Clear SSE exceptions.  */
-      temp.__mxcsr &= ~FE_ALL_EXCEPT;
+      temp.__mxcsr &= ~FE_ALL_EXCEPT_X86;
       /* Set mask for SSE MXCSR.  */
       /* Set rounding to FE_TONEAREST.  */
       temp.__mxcsr &= ~ 0x6000;
       temp.__mxcsr |= (FE_TONEAREST << 3);
       /* Do not mask exceptions.  */
       temp.__mxcsr &= ~(FE_ALL_EXCEPT << 7);
+      /* Keep the "denormal operand" exception masked.  */
+      temp.__mxcsr |= (__FE_DENORM << 7);
+      /* Clear the FZ and DAZ bits.  */
+      temp.__mxcsr &= ~0x8040;
     }
   else
     {
-      temp.__control_word &= ~(FE_ALL_EXCEPT | FE_TOWARDZERO);
+      temp.__control_word &= ~(FE_ALL_EXCEPT_X86
+			       | FE_TOWARDZERO
+			       | _FPU_EXTENDED);
       temp.__control_word |= (envp->__control_word
-			      & (FE_ALL_EXCEPT | FE_TOWARDZERO));
-      temp.__status_word &= ~FE_ALL_EXCEPT;
-      temp.__status_word |= envp->__status_word & FE_ALL_EXCEPT;
+			      & (FE_ALL_EXCEPT_X86
+				 | FE_TOWARDZERO
+				 | _FPU_EXTENDED));
+      temp.__status_word &= ~FE_ALL_EXCEPT_X86;
+      temp.__status_word |= envp->__status_word & FE_ALL_EXCEPT_X86;
       temp.__eip = envp->__eip;
       temp.__cs_selector = envp->__cs_selector;
       temp.__opcode = envp->__opcode;