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Rewrite feupdateenv

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This patch rewrites feupdateenv to improve performance by avoiding
unnecessary FPSCR reads/writes. It fixes bug 16918 by passing the
correct return value.

2014-06-24  Wilco  <wdijkstr@arm.com>

	[BZ #16918]
	* sysdeps/arm/feupdateenv.c (feupdateenv):
	Rewrite to reduce FPSCR accesses and fix return value.
This commit is contained in:
Wilco 2014-06-24 13:53:04 +00:00
parent 001f7b773c
commit db59bad394
2 changed files with 44 additions and 6 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2014-06-24 Wilco <wdijkstr@arm.com>
[BZ #16918]
* sysdeps/arm/feupdateenv.c (feupdateenv):
Rewrite to reduce FPSCR accesses and fix return value.
2014-06-24 Wilco <wdijkstr@arm.com>
* sysdeps/arm/fclrexcpt.c (feclearexcept):

44
sysdeps/arm/feupdateenv.c
View File

@ -18,26 +18,58 @@
<http://www.gnu.org/licenses/>. */
#include <fenv.h>
#include <fpu_control.h>
#include <arm-features.h>
int
feupdateenv (const fenv_t *envp)
{
fpu_control_t fpscr;
fpu_control_t fpscr, new_fpscr, updated_fpscr;
int excepts;
/* Fail if a VFP unit isn't present. */
if (!ARM_HAVE_VFP)
return 1;
_FPU_GETCW (fpscr);
excepts = fpscr & FE_ALL_EXCEPT;
/* Install new environment. */
fesetenv (envp);
if ((envp != FE_DFL_ENV) && (envp != FE_NOMASK_ENV))
{
/* Merge current exception flags with the saved fenv. */
new_fpscr = envp->__cw | excepts;
/* Write new FPSCR if different (ignoring NZCV flags). */
if (((fpscr ^ new_fpscr) & ~_FPU_MASK_NZCV) != 0)
_FPU_SETCW (new_fpscr);
/* Raise the exceptions if enabled in the new FP state. */
if (excepts & (new_fpscr >> FE_EXCEPT_SHIFT))
return feraiseexcept (excepts);
return 0;
}
/* Preserve the reserved FPSCR flags. */
new_fpscr = fpscr & (_FPU_RESERVED | FE_ALL_EXCEPT);
new_fpscr |= (envp == FE_DFL_ENV) ? _FPU_DEFAULT : _FPU_IEEE;
if (((new_fpscr ^ fpscr) & ~_FPU_MASK_NZCV) != 0)
{
_FPU_SETCW (new_fpscr);
/* Not all VFP architectures support trapping exceptions, so
test whether the relevant bits were set and fail if not. */
_FPU_GETCW (updated_fpscr);
if (new_fpscr & ~updated_fpscr)
return 1;
}
/* Raise the exceptions if enabled in the new FP state. */
if (excepts & (new_fpscr >> FE_EXCEPT_SHIFT))
return feraiseexcept (excepts);
/* Raise the saved exceptions. */
feraiseexcept (fpscr & FE_ALL_EXCEPT);
return 0;
}
libm_hidden_def (feupdateenv)