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commit 7b8481b330720d28c019a2e5994492a1923d5daa
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Author: Paul A. Clarke <pc@us.ibm.com>
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Date: Thu Sep 19 11:11:04 2019 -0500
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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
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"Ignore Exceptions Mode", and doing so conditionally requires
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- the conditional logic, and
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- a system call.
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Make it a no-op for uses within glibc.
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diff --git a/sysdeps/powerpc/fpu/fenv_private.h b/sysdeps/powerpc/fpu/fenv_private.h
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index 666fbfdd9fef7759..e09137e892a8e3f3 100644
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--- a/sysdeps/powerpc/fpu/fenv_private.h
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+++ b/sysdeps/powerpc/fpu/fenv_private.h
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@@ -23,6 +23,17 @@
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#include <fenv_libc.h>
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#include <fpu_control.h>
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+#ifdef _ARCH_PWR8
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+/* There is no performance advantage to non-stop mode. */
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+/* The odd syntax here is to innocuously reference the given variables
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+ to prevent warnings about unused variables. */
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+#define __TEST_AND_BEGIN_NON_STOP(old, new) do {} while ((old) * (new) * 0 != 0)
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+#define __TEST_AND_END_NON_STOP(old, new) do {} while ((old) * (new) * 0 != 0)
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+#else
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+#define __TEST_AND_BEGIN_NON_STOP __TEST_AND_ENTER_NON_STOP
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+#define __TEST_AND_END_NON_STOP __TEST_AND_EXIT_NON_STOP
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+#endif
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+
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static __always_inline void
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libc_feholdexcept_setround_ppc (fenv_t *envp, int r)
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{
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@@ -30,7 +41,7 @@ libc_feholdexcept_setround_ppc (fenv_t *envp, int r)
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old.fenv = *envp = fegetenv_register ();
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- __TEST_AND_ENTER_NON_STOP (old.l, 0ULL);
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+ __TEST_AND_BEGIN_NON_STOP (old.l, 0ULL);
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/* Clear everything and set the rounding mode. */
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new.l = r;
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@@ -49,8 +60,8 @@ __libc_femergeenv_ppc (const fenv_t *envp, unsigned long long old_mask,
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/* Merge bits while masking unwanted bits from new and old env. */
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new.l = (old.l & old_mask) | (new.l & new_mask);
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- __TEST_AND_EXIT_NON_STOP (old.l, new.l);
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- __TEST_AND_ENTER_NON_STOP (old.l, new.l);
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+ __TEST_AND_END_NON_STOP (old.l, new.l);
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+ __TEST_AND_BEGIN_NON_STOP (old.l, new.l);
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/* If requesting to keep status, replace control, and merge exceptions,
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and exceptions haven't changed, we can just set new control instead
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@@ -141,7 +152,7 @@ libc_feholdsetround_noex_ppc_ctx (struct rm_ctx *ctx, int r)
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ctx->env = old.fenv;
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if (__glibc_unlikely (new.l != old.l))
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{
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- __TEST_AND_ENTER_NON_STOP (old.l, 0ULL);
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+ __TEST_AND_BEGIN_NON_STOP (old.l, 0ULL);
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fesetenv_control (new.fenv);
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ctx->updated_status = true;
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}
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