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[powerpc] fesetenv: optimize FPSCR access

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fesetenv() reads the current value of the Floating-Point Status and Control
Register (FPSCR) to determine the difference between the current state of
exception enables and the newly requested state.  All of these bits are also
returned by the lighter weight 'mffsl' instruction used by fegetenv_status().
Use that instead.

Also, remove a local macro _FPU_MASK_ALL in favor of a common macro,
FPU_ENABLES_MASK from fenv_libc.h.

Finally, use a local variable ('new') in favor of a pointer dereference
('*envp').
This commit is contained in:
Paul A. Clarke 2019-08-06 00:13:45 -04:00
parent e905212627
commit fec2bd2c2d
2 changed files with 10 additions and 8 deletions
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6
ChangeLog
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@ -1,3 +1,9 @@
2019-08-28 Paul A. Clarke <pc@us.ibm.com>
* sysdeps/powerpc/fpu/fesetenv.c (__fesetenv): Utilize lightweight
FPSCR read.
(_FPU_MASK_ALL): Delete.
2019-08-28 Paul A. Clarke <pc@us.ibm.com>
* sysdeps/powerpc/fpu/fenv_private.h (libc_feholdsetround_ppc_ctx):

12
sysdeps/powerpc/fpu/fesetenv.c
View File

@ -19,8 +19,6 @@
#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
__fesetenv (const fenv_t *envp)
{
@ -28,25 +26,23 @@ __fesetenv (const fenv_t *envp)
/* get the currently set exceptions. */
new.fenv = *envp;
old.fenv = fegetenv_register ();
if (old.l == new.l)
return 0;
old.fenv = fegetenv_status ();
/* 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 & _FPU_MASK_ALL) == 0 && (new.l & _FPU_MASK_ALL) != 0)
if ((old.l & FPSCR_ENABLES_MASK) == 0 && (new.l & FPSCR_ENABLES_MASK) != 0)
(void) __fe_nomask_env_priv ();
/* 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 & _FPU_MASK_ALL) != 0 && (new.l & _FPU_MASK_ALL) == 0)
if ((old.l & FPSCR_ENABLES_MASK) != 0 && (new.l & FPSCR_ENABLES_MASK) == 0)
(void)__fe_mask_env ();
fesetenv_register (*envp);
fesetenv_register (new.fenv);
/* Success. */
return 0;