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[powerpc] No need to enter "Ignore Exceptions Mode"

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Since at least POWER8, there is no performance advantage to entering
"Ignore Exceptions Mode", and doing so conditionally requires
 - the conditional logic, and
 - a system call.

Make it a no-op for uses within glibc.
This commit is contained in:
Paul A. Clarke 2019-09-19 11:11:04 -05:00
parent 21417aaa88
commit 7b8481b330
1 changed files with 15 additions and 4 deletions
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19
sysdeps/powerpc/fpu/fenv_private.h
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@ -23,6 +23,17 @@
#include <fenv_libc.h>
#include <fpu_control.h>
#ifdef _ARCH_PWR8
/* There is no performance advantage to non-stop mode. */
/* The odd syntax here is to innocuously reference the given variables
to prevent warnings about unused variables. */
#define __TEST_AND_BEGIN_NON_STOP(old, new) do {} while ((old) * (new) * 0 != 0)
#define __TEST_AND_END_NON_STOP(old, new) do {} while ((old) * (new) * 0 != 0)
#else
#define __TEST_AND_BEGIN_NON_STOP __TEST_AND_ENTER_NON_STOP
#define __TEST_AND_END_NON_STOP __TEST_AND_EXIT_NON_STOP
#endif
static __always_inline void
libc_feholdexcept_setround_ppc (fenv_t *envp, int r)
{
@ -30,7 +41,7 @@ libc_feholdexcept_setround_ppc (fenv_t *envp, int r)
old.fenv = *envp = fegetenv_register ();
__TEST_AND_ENTER_NON_STOP (old.l, 0ULL);
__TEST_AND_BEGIN_NON_STOP (old.l, 0ULL);
/* Clear everything and set the rounding mode. */
new.l = r;
@ -49,8 +60,8 @@ __libc_femergeenv_ppc (const fenv_t *envp, unsigned long long old_mask,
/* Merge bits while masking unwanted bits from new and old env. */
new.l = (old.l & old_mask) | (new.l & new_mask);
__TEST_AND_EXIT_NON_STOP (old.l, new.l);
__TEST_AND_ENTER_NON_STOP (old.l, new.l);
__TEST_AND_END_NON_STOP (old.l, new.l);
__TEST_AND_BEGIN_NON_STOP (old.l, new.l);
/* If requesting to keep status, replace control, and merge exceptions,
and exceptions haven't changed, we can just set new control instead
@ -141,7 +152,7 @@ libc_feholdsetround_noex_ppc_ctx (struct rm_ctx *ctx, int r)
ctx->env = old.fenv;
if (__glibc_unlikely (new.l != old.l))
{
__TEST_AND_ENTER_NON_STOP (old.l, 0ULL);
__TEST_AND_BEGIN_NON_STOP (old.l, 0ULL);
fesetenv_control (new.fenv);
ctx->updated_status = true;
}