[BZ #6411]

2008-11-13  Ryan S. Arnold  <rsa@us.ibm.com>
	[BZ #6411]
	* sysdeps/powerpc/fpu/Makefile: Added test case tst-setcontext-fpscr.
	* sysdeps/powerpc/fpu/feholdexcpt.c (_FPU_MASK_ALL): Define to replace
	magic numbers.
	* sysdeps/powerpc/fpu/fenv_libc.h (fesetenv_register): Dynamically
	choose mtfsf insn based on PPC_FEATURE_HAS_DFP.
	(relax_fenv_state): Same as above.
	(FPSCR_29): Reserve bit in ISA 2.05.
	(FPSCR_NI): Provide define for compat.
	* sysdeps/powerpc/fpu/fesetenv.c (_FPU_MASK_ALL): Define to replace
	magic numbers.
	* sysdeps/powerpc/fpu/feupdateenv.c (_FPU_MASK_ALL): Define to replace
	magic numbers.
	* sysdeps/powerpc/fpu/tst-setcontext-fpscr.c: New file.  Test case to
	test setcontext and swapcontext with dynamic 64-bit FPSCR detection.
	* sysdeps/powerpc/powerpc32/fpu/__longjmp-common.S (__longjmp): Adjust
	access to hwcap to account for hwcap size increase to uint64_t.
	* sysdeps/powerpc/powerpc32/fpu/setjmp-common.S (__sigsetjmp ):
	Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/getcontext-common.S
	(*setcontext): Likewise.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/power6/fpu/setcontext.S:
	New file.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/power6/fpu/swapcontext.S:
	New file.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/setcontext-common.S
	(*setcontext): dynamically select mtfsf insn based on
	PPC_FEATURE_HAS_DFP. Adjust access to hwcap to account for hwcap size
	increase to uint64_t.
	* sysdeps/unix/sysv/linux/powerpc/powerpc32/swapcontext-common.S
	(*swapcontext): dynamically select mtfsf insn based on
	PPC_FEATURE_HAS_DFP.  Adjust access to hwcap to account for hwcap size
	increase to uint64_t.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/power6/fpu/setcontext.S:
	New file.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/power6/fpu/swapcontext.S:
	New file.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/setcontext.S
	(*setcontext): dynamically select mtfsf insn based on
	PPC_FEATURE_HAS_DFP.
	* sysdeps/unix/sysv/linux/powerpc/powerpc64/swapcontext.S
	(*swapcontext): dynamically select mtfsf insn based on
	PPC_FEATURE_HAS_DFP.

6 files changed, 409 insertions, 15 deletions

diff --git a/sysdeps/powerpc/fpu/Makefile b/sysdeps/powerpc/fpu/Makefile
index ce67ff87df..ffacf1a754 100644
--- a/sysdeps/powerpc/fpu/Makefile
+++ b/sysdeps/powerpc/fpu/Makefile
@@ -5,3 +5,7 @@ libm-tests += test-powerpc-snan
 # libm needs ld.so to access dl_hwcap
 $(objpfx)libm.so: $(elfobjdir)/ld.so
 endif
+
+ifeq ($(subdir),stdlib)
+tests += tst-setcontext-fpscr
+endif
diff --git a/sysdeps/powerpc/fpu/feholdexcpt.c b/sysdeps/powerpc/fpu/feholdexcpt.c
index c9432248db..b74b18aded 100644
--- a/sysdeps/powerpc/fpu/feholdexcpt.c
+++ b/sysdeps/powerpc/fpu/feholdexcpt.c
@@ -1,5 +1,5 @@
 /* Store current floating-point environment and clear exceptions.
-   Copyright (C) 1997, 2005 Free Software Foundation, Inc.
+   Copyright (C) 1997, 2005, 2008 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
@@ -18,6 +18,8 @@
    02111-1307 USA.  */
 
 #include <fenv_libc.h>
+#include <fpu_control.h>
+#define _FPU_MASK_ALL (_FPU_MASK_ZM | _FPU_MASK_OM | _FPU_MASK_UM | _FPU_MASK_XM | _FPU_MASK_IM)
 
 int
 feholdexcept (fenv_t *envp)
@@ -35,7 +37,7 @@ feholdexcept (fenv_t *envp)
   /* If the old env had any eabled exceptions, then mask SIGFPE in the
      MSR FE0/FE1 bits.  This may allow the FPU to run faster because it
      always takes the default action and can not generate SIGFPE. */
-  if ((old.l[1] & 0x000000F8) != 0)
+  if ((old.l[1] & _FPU_MASK_ALL) != 0)
     (void)__fe_mask_env ();
 
   /* Put the new state in effect.  */
diff --git a/sysdeps/powerpc/fpu/fenv_libc.h b/sysdeps/powerpc/fpu/fenv_libc.h
index 6f116b60d5..c70f85130d 100644
--- a/sysdeps/powerpc/fpu/fenv_libc.h
+++ b/sysdeps/powerpc/fpu/fenv_libc.h
@@ -21,6 +21,8 @@
 #define _FENV_LIBC_H	1
 
 #include <fenv.h>
+#include <ldsodefs.h>
+#include <sysdep.h>
 
 libm_hidden_proto (__fe_nomask_env)
 
@@ -34,7 +36,13 @@ libm_hidden_proto (__fe_nomask_env)
 
 /* Equivalent to fesetenv, but takes a fenv_t instead of a pointer.  */
 #define fesetenv_register(env) \
-        ({ double d = (env); asm volatile ("mtfsf 0xff,%0" : : "f" (d)); })
+	do { \
+	  double d = (env); \
+	  if(GLRO(dl_hwcap) & PPC_FEATURE_HAS_DFP) \
+	    asm volatile ("mtfsf 0xff,%0,1,0" : : "f" (d)); \
+	  else \
+	    asm volatile ("mtfsf 0xff,%0" : : "f" (d)); \
+	} while(0)
 
 /* This very handy macro:
    - Sets the rounding mode to 'round to nearest';
@@ -42,7 +50,12 @@ libm_hidden_proto (__fe_nomask_env)
    - Prevents exceptions from being raised for inexact results.
    These things happen to be exactly what you need for typical elementary
    functions.  */
-#define relax_fenv_state() asm ("mtfsfi 7,0")
+#define relax_fenv_state() \
+	do { \
+	   if(GLRO(dl_hwcap) & PPC_FEATURE_HAS_DFP) \
+	       asm ("mtfsfi 7,0,1"); \
+	   asm ("mtfsfi 7,0"); \
+	} while(0)
 
 /* Set/clear a particular FPSCR bit (for instance,
    reset_fpscr_bit(FPSCR_VE);
@@ -122,10 +135,19 @@ enum {
   FPSCR_UE,        /* underflow exception enable */
   FPSCR_ZE,        /* zero divide exception enable */
   FPSCR_XE,        /* inexact exception enable */
+#ifdef _ARCH_PWR6
+  FPSCR_29,        /* Reserved in ISA 2.05  */
+#else
   FPSCR_NI         /* non-IEEE mode (typically, no denormalised numbers) */
+#endif /* _ARCH_PWR6 */
   /* the remaining two least-significant bits keep the rounding mode */
 };
 
+#ifdef _ARCH_PWR6
+  /* Not supported in ISA 2.05.  Provided for source compat only.  */
+# define FPSCR_NI 29
+#endif /* _ARCH_PWR6 */
+
 /* This operation (i) sets the appropriate FPSCR bits for its
    parameter, (ii) converts SNaN to the corresponding NaN, and (iii)
    otherwise passes its parameter through unchanged (in particular, -0
diff --git a/sysdeps/powerpc/fpu/fesetenv.c b/sysdeps/powerpc/fpu/fesetenv.c
index 5a0c742ffe..fa81d78211 100644
--- a/sysdeps/powerpc/fpu/fesetenv.c
+++ b/sysdeps/powerpc/fpu/fesetenv.c
@@ -1,5 +1,6 @@
 /* Install given floating-point environment.
-   Copyright (C) 1997,99,2000,01,02,07 Free Software Foundation, Inc.
+   Copyright (C) 1997, 1999, 2000, 2001, 2007, 2008
+   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
@@ -18,8 +19,11 @@
    02111-1307 USA.  */
 
 #include <fenv_libc.h>
+#include <fpu_control.h>
 #include <bp-sym.h>
 
+#define _FPU_MASK_ALL (_FPU_MASK_ZM | _FPU_MASK_OM | _FPU_MASK_UM | _FPU_MASK_XM | _FPU_MASK_IM)
+
 int
 __fesetenv (const fenv_t *envp)
 {
@@ -29,18 +33,18 @@ __fesetenv (const fenv_t *envp)
   new.fenv = *envp;
   old.fenv = fegetenv_register ();
   
-  /* If the old env has no eabled exceptions and the new env has any enabled
-     exceptions, then unmask SIGFPE in the MSR FE0/FE1 bits.  This will put
-     the hardware into "precise mode" and may cause the FPU to run slower on
-     some hardware.  */
-  if ((old.l[1] & 0x000000F8) == 0 && (new.l[1] & 0x000000F8) != 0)
+  /* If the old env has no enabled exceptions and the new env has any enabled
+     exceptions, then unmask SIGFPE in the MSR FE0/FE1 bits.  This will put the
+     hardware into "precise mode" and may cause the FPU to run slower on some
+     hardware.  */
+  if ((old.l[1] & _FPU_MASK_ALL) == 0 && (new.l[1] & _FPU_MASK_ALL) != 0)
     (void)__fe_nomask_env ();
   
-  /* If the old env had any eabled exceptions and the new env has no enabled
+  /* If the old env had any enabled exceptions and the new env has no enabled
      exceptions, then mask SIGFPE in the MSR FE0/FE1 bits.  This may allow the
      FPU to run faster because it always takes the default action and can not 
      generate SIGFPE. */
-  if ((old.l[1] & 0x000000F8) != 0 && (new.l[1] & 0x000000F8) == 0)
+  if ((old.l[1] & _FPU_MASK_ALL) != 0 && (new.l[1] & _FPU_MASK_ALL) == 0)
     (void)__fe_mask_env ();
     
   fesetenv_register (*envp);
diff --git a/sysdeps/powerpc/fpu/feupdateenv.c b/sysdeps/powerpc/fpu/feupdateenv.c
index 5a4000f599..5fca301fe5 100644
--- a/sysdeps/powerpc/fpu/feupdateenv.c
+++ b/sysdeps/powerpc/fpu/feupdateenv.c
@@ -1,5 +1,6 @@
 /* Install given floating-point environment and raise exceptions.
-   Copyright (C) 1997,99,2000,01,07 Free Software Foundation, Inc.
+   Copyright (C) 1997, 1999, 2000, 2001, 2007, 2008
+   Free Software Foundation, Inc.
    This file is part of the GNU C Library.
    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
 
@@ -19,8 +20,11 @@
    02111-1307 USA.  */
 
 #include <fenv_libc.h>
+#include <fpu_control.h>
 #include <bp-sym.h>
 
+#define _FPU_MASK_ALL (_FPU_MASK_ZM | _FPU_MASK_OM | _FPU_MASK_UM | _FPU_MASK_XM | _FPU_MASK_IM)
+
 int
 __feupdateenv (const fenv_t *envp)
 {
@@ -39,14 +43,14 @@ __feupdateenv (const fenv_t *envp)
      exceptions, then unmask SIGFPE in the MSR FE0/FE1 bits.  This will put
      the hardware into "precise mode" and may cause the FPU to run slower on
      some hardware.  */
-  if ((old.l[1] & 0x000000F8) == 0 && (new.l[1] & 0x000000F8) != 0)
+  if ((old.l[1] & _FPU_MASK_ALL) == 0 && (new.l[1] & _FPU_MASK_ALL) != 0)
     (void)__fe_nomask_env ();
   
   /* If the old env had any eabled exceptions and the new env has no enabled
      exceptions, then mask SIGFPE in the MSR FE0/FE1 bits.  This may allow the
      FPU to run faster because it always takes the default action and can not 
      generate SIGFPE. */
-  if ((old.l[1] & 0x000000F8) != 0 && (new.l[1] & 0x000000F8) == 0)
+  if ((old.l[1] & _FPU_MASK_ALL) != 0 && (new.l[1] & _FPU_MASK_ALL) == 0)
     (void)__fe_mask_env ();
 
   /* Atomically enable and raise (if appropriate) exceptions set in `new'. */
diff --git a/sysdeps/powerpc/fpu/tst-setcontext-fpscr.c b/sysdeps/powerpc/fpu/tst-setcontext-fpscr.c
new file mode 100644
index 0000000000..973fb3f77a
--- /dev/null
+++ b/sysdeps/powerpc/fpu/tst-setcontext-fpscr.c
@@ -0,0 +1,358 @@
+/* Copyright (C) 2001,2002,2004,2006,2007,2008 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ryan S. Arnold <rsa@us.ibm.com>
+                  Sean Curry <spcurry@us.ibm.com>
+
+   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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ucontext.h>
+#include <unistd.h>
+#include <malloc.h>
+#include <link.h>
+#include <elf.h>
+#include <sysdep.h>
+#include <fpu_control.h>
+
+static ucontext_t ctx[3];
+
+
+volatile int global;
+
+
+static int back_in_main;
+
+
+volatile static ElfW(auxv_t) *auxv = NULL;
+
+ElfW(Addr) query_auxv(int type)
+{
+  FILE *auxv_f;
+  ElfW(auxv_t) auxv_struct;
+  ElfW(auxv_t) *auxv_temp;
+  int i = 0;
+
+  /* if the /proc/self/auxv file has not been manually copied into the heap
+     yet, then do it */
+
+  if(auxv == NULL)
+    {
+      auxv_f = fopen("/proc/self/auxv", "r");
+
+      if(auxv_f == 0)
+	{
+	  perror("Error opening file for reading");
+	  return 0;
+	}
+      auxv = (ElfW(auxv_t) *)malloc(getpagesize());
+
+      do
+	{
+	  fread(&auxv_struct, sizeof(ElfW(auxv_t)), 1, auxv_f);
+	  auxv[i] = auxv_struct;
+	  i++;
+	} while(auxv_struct.a_type != AT_NULL);
+    }
+
+  auxv_temp = (ElfW(auxv_t) *)auxv;
+  i = 0;
+  do
+    {
+      if(auxv_temp[i].a_type == type)
+	{
+	  return auxv_temp[i].a_un.a_val;
+	}
+      i++;
+    } while (auxv_temp[i].a_type != AT_NULL);
+
+  return 0;
+}
+
+typedef unsigned long long di_fpscr_t __attribute__ ((__mode__ (__DI__)));
+typedef unsigned int si_fpscr_t __attribute__ ((__mode__ (__SI__)));
+
+#define _FPSCR_RESERVED 0xfffffff8ffffff04ULL
+
+#define _FPSCR_TEST0_DRN 0x0000000400000000ULL
+#define _FPSCR_TEST0_RN  0x0000000000000003ULL
+
+#define _FPSCR_TEST1_DRN 0x0000000300000000ULL
+#define _FPSCR_TEST1_RN  0x0000000000000002ULL
+
+/* Macros for accessing the hardware control word on Power6[x].  */
+# define _GET_DI_FPSCR(__fpscr) ({					     \
+   union { double d;							     \
+           di_fpscr_t fpscr; }						     \
+     tmp __attribute__ ((__aligned__(8)));				     \
+   __asm__ ("mffs 0; stfd%U0 0,%0" : "=m" (tmp.d) : : "fr0");		     \
+   (__fpscr)=tmp.fpscr;							     \
+   tmp.fpscr; })
+
+# define _SET_DI_FPSCR(__fpscr) {					     \
+  union { double d; di_fpscr_t fpscr; }					     \
+    tmp __attribute__ ((__aligned__(8)));				     \
+  tmp.fpscr = __fpscr;							     \
+  /* Set the entire 64-bit FPSCR.  */					     \
+  __asm__ ("lfd%U0 0,%0; mtfsf 255,0,1,0" : : "m" (tmp.d) : "fr0");	     \
+}
+
+# define _GET_SI_FPSCR(__fpscr) ({					     \
+   union { double d;							     \
+           si_fpscr_t cw[2]; }						     \
+     tmp __attribute__ ((__aligned__(8)));				     \
+   __asm__ ("mffs 0; stfd%U0 0,%0" : "=m" (tmp.d) : : "fr0");		     \
+   (__fpscr)=tmp.cw[1];							     \
+   tmp.cw[0]; })
+
+# define _SET_SI_FPSCR(__fpscr) {					     \
+  union { double d; si_fpscr_t fpscr[2]; }				     \
+    tmp __attribute__ ((__aligned__(8)));				     \
+  /* More-or-less arbitrary; this is a QNaN. */				     \
+  tmp.fpscr[0] = 0xFFF80000;						     \
+  tmp.fpscr[1] = __fpscr;						     \
+  __asm__ ("lfd%U0 0,%0; mtfsf 255,0" : : "m" (tmp.d) : "fr0");		     \
+}
+
+void prime_special_regs(int which)
+{
+  ElfW(Addr) a_val;
+
+  di_fpscr_t di_fpscr __attribute__ ((__aligned__(8)));
+
+  a_val = query_auxv(AT_HWCAP);
+  if(a_val == -1)
+    {
+      puts ("querying the auxv for the hwcap failed");
+      _exit (1);
+    }
+
+  /* Indicates a 64-bit FPSCR.  */
+  if (a_val & PPC_FEATURE_HAS_DFP)
+    {
+      _GET_DI_FPSCR(di_fpscr);
+
+      /* Overwrite the existing DRN and RN if there is one.  */
+      if (which == 0)
+        di_fpscr = ((di_fpscr & _FPSCR_RESERVED) | (_FPSCR_TEST0_DRN | _FPSCR_TEST0_RN));
+      else
+        di_fpscr = ((di_fpscr & _FPSCR_RESERVED) | (_FPSCR_TEST1_DRN | _FPSCR_TEST1_RN));
+      puts ("Priming 64-bit FPSCR with:");
+      printf("0x%.16llx\n",(unsigned long long int)di_fpscr);
+
+      _SET_DI_FPSCR(di_fpscr);
+    }
+  else
+    {
+      puts ("32-bit FPSCR found and will be tested.");
+      _GET_SI_FPSCR(di_fpscr);
+
+      /* Overwrite the existing RN if there is one.  */
+      if (which == 0)
+        di_fpscr = ((di_fpscr & _FPSCR_RESERVED) | (_FPSCR_TEST0_RN));
+      else
+        di_fpscr = ((di_fpscr & _FPSCR_RESERVED) | (_FPSCR_TEST1_RN));
+      puts ("Priming 32-bit FPSCR with:");
+      printf("0x%.8lx\n",(unsigned long int) di_fpscr);
+
+      _SET_SI_FPSCR(di_fpscr);
+    }
+}
+
+void clear_special_regs(void)
+{
+  ElfW(Addr) a_val;
+
+  di_fpscr_t di_fpscr __attribute__ ((__aligned__(8)));
+
+  union {
+	  double d;
+	  unsigned long long int lli;
+	  unsigned int li[2];
+  } dlli;
+
+  a_val = query_auxv(AT_HWCAP);
+  if(a_val == -1)
+    {
+      puts ("querying the auxv for the hwcap failed");
+      _exit (1);
+    }
+
+#if __WORDSIZE == 32
+  dlli.d = ctx[0].uc_mcontext.uc_regs->fpregs.fpscr;
+#else
+  dlli.d = ctx[0].uc_mcontext.fp_regs[32];
+#endif
+
+  puts("The FPSCR value saved in the ucontext_t is:");
+
+  /* Indicates a 64-bit FPSCR.  */
+  if (a_val & PPC_FEATURE_HAS_DFP)
+    {
+      printf("0x%.16llx\n",dlli.lli);
+      di_fpscr = 0x0;
+      puts ("Clearing the 64-bit FPSCR to:");
+      printf("0x%.16llx\n",(unsigned long long int) di_fpscr);
+
+      _SET_DI_FPSCR(di_fpscr);
+    }
+  else
+    {
+      printf("0x%.8x\n",(unsigned int) dlli.li[1]);
+      di_fpscr = 0x0;
+      puts ("Clearing the 32-bit FPSCR to:");
+      printf("0x%.8lx\n",(unsigned long int) di_fpscr);
+
+      _SET_SI_FPSCR(di_fpscr);
+    }
+}
+
+void test_special_regs(int which)
+{
+  ElfW(Addr) a_val;
+  unsigned long long int test;
+
+  di_fpscr_t di_fpscr __attribute__ ((__aligned__(8)));
+
+  a_val = query_auxv(AT_HWCAP);
+  if(a_val == -1)
+    {
+      puts ("querying the auxv for the hwcap failed");
+      _exit (2);
+    }
+
+  /* Indicates a 64-bit FPSCR.  */
+  if (a_val & PPC_FEATURE_HAS_DFP)
+    {
+      _GET_DI_FPSCR(di_fpscr);
+
+      if (which == 0)
+	puts ("After setcontext the 64-bit FPSCR contains:");
+      else
+	puts ("After swapcontext the 64-bit FPSCR contains:");
+
+      printf("0x%.16llx\n",(unsigned long long int) di_fpscr);
+      test = (_FPSCR_TEST0_DRN | _FPSCR_TEST0_RN);
+      if((di_fpscr & (test)) != (test))
+        {
+	  printf ("%s: DRN and RN bits set before getcontext were not preserved across [set|swap]context call: %m",__FUNCTION__);
+	  _exit (3);
+        }
+    }
+  else
+    {
+      _GET_SI_FPSCR(di_fpscr);
+      if (which == 0)
+	puts ("After setcontext the 32-bit FPSCR contains:");
+      else
+	puts ("After swapcontext the 32-bit FPSCR contains:");
+
+      printf("0x%.8lx\n",(unsigned long int) di_fpscr);
+      test = _FPSCR_TEST0_RN;
+      if((di_fpscr & test) != test)
+        {
+	  printf ("%s: RN bit set before getcontext was not preserved across [set|swap]context call: %m",__FUNCTION__);
+	  _exit (4);
+        }
+    }
+}
+
+
+static void
+check_called (void)
+{
+  if (back_in_main == 0)
+    {
+      puts ("program did not reach main again");
+      _exit (5);
+    }
+}
+
+
+int
+main (void)
+{
+  atexit (check_called);
+
+  puts ("priming the FPSCR with a marker");
+  prime_special_regs (0);
+
+  puts ("making contexts");
+  if (getcontext (&ctx[0]) != 0)
+    {
+      if (errno == ENOSYS)
+	{
+	  back_in_main = 1;
+	  exit (0);
+	}
+
+      printf ("%s: getcontext: %m\n", __FUNCTION__);
+      exit (6);
+    }
+
+  /* Play some tricks with this context.  */
+  if (++global == 1)
+    {
+    clear_special_regs ( );
+    if (setcontext (&ctx[0]) != 0)
+      {
+	printf ("%s: setcontext: %m\n", __FUNCTION__);
+	exit (7);
+      }
+    }
+  if (global != 2)
+    {
+      printf ("%s: 'global' not incremented twice\n", __FUNCTION__);
+      exit (8);
+    }
+
+  test_special_regs (0);
+
+  global = 0;
+  if (getcontext (&ctx[0]) != 0)
+    {
+      printf ("%s: getcontext: %m\n", __FUNCTION__);
+      exit (9);
+    }
+
+  if (++global == 1)
+    {
+      puts ("priming the FPSCR with a marker");
+      prime_special_regs (1);
+
+      puts ("swapping contexts");
+      if (swapcontext (&ctx[1], &ctx[0]) != 0)
+        {
+          printf ("%s: swapcontext: %m\n", __FUNCTION__);
+          exit (9);
+        }
+    }
+  if (global != 2)
+    {
+      printf ("%s: 'global' not incremented twice\n", __FUNCTION__);
+      exit (10);
+    }
+
+  test_special_regs (1);
+
+  puts ("back at main program");
+  back_in_main = 1;
+
+  puts ("test succeeded");
+  return 0;
+}