glibc/SOURCES/glibc-rh1783303-18.patch

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2020-07-28 07:00:40 +00:00
commit 7b8481b330720d28c019a2e5994492a1923d5daa
Author: Paul A. Clarke <pc@us.ibm.com>
Date: Thu Sep 19 11:11:04 2019 -0500
[powerpc] No need to enter "Ignore Exceptions Mode"
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.
diff --git a/sysdeps/powerpc/fpu/fenv_private.h b/sysdeps/powerpc/fpu/fenv_private.h
index 666fbfdd9fef7759..e09137e892a8e3f3 100644
--- a/sysdeps/powerpc/fpu/fenv_private.h
+++ b/sysdeps/powerpc/fpu/fenv_private.h
@@ -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;
}