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* [glibc] fegetenv_and_set_rn now uses the builtins provided by GCC.
@ 2023-09-27 16:57 Adhemerval Zanella
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From: Adhemerval Zanella @ 2023-09-27 16:57 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=4eac1825ed92e88c192abb436412d5fb84ddd854
commit 4eac1825ed92e88c192abb436412d5fb84ddd854
Author: Manjunath Matti <mmatti@linux.ibm.com>
Date: Sat Sep 23 10:49:51 2023 -0500
fegetenv_and_set_rn now uses the builtins provided by GCC.
On powerpc, SET_RESTORE_ROUND uses inline assembly to optimize the
prologue get/save/set rounding mode operations for POWER9 and
later by using 'mffscrn' where possible, this was introduced by
commit f1c56cdff09f650ad721fae026eb6a3651631f3d.
GCC version 14 onwards supports builtins as __builtin_set_fpscr_rn
which now returns the FPSCR fields in a double. This feature is
available on Power9 when the __SET_FPSCR_RN_RETURNS_FPSCR__ macro
is defined.
GCC commit ef3bbc69d15707e4db6e2f198c621effb636cc26 adds
this feature.
Changes are done to use __builtin_set_fpscr_rn instead of mffscrn
or mffscrni in __fe_mffscrn(rn).
Suggested-by: Carl Love <cel@us.ibm.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Diff:
---
sysdeps/powerpc/fpu/fenv_libc.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/sysdeps/powerpc/fpu/fenv_libc.h b/sysdeps/powerpc/fpu/fenv_libc.h
index fa5e1c697e..a2a12d914b 100644
--- a/sysdeps/powerpc/fpu/fenv_libc.h
+++ b/sysdeps/powerpc/fpu/fenv_libc.h
@@ -68,6 +68,14 @@ extern const fenv_t *__fe_mask_env (void) attribute_hidden;
__fr; \
})
+/* Starting with GCC 14 __builtin_set_fpscr_rn can be used to return the
+ FPSCR fields as a double. This support is available
+ on Power9 when the __SET_FPSCR_RN_RETURNS_FPSCR__ macro is defined.
+ To retain backward compatibility with older GCC, we still retain the
+ old inline assembly implementation.*/
+#ifdef __SET_FPSCR_RN_RETURNS_FPSCR__
+#define __fe_mffscrn(rn) __builtin_set_fpscr_rn (rn)
+#else
#define __fe_mffscrn(rn) \
({register fenv_union_t __fr; \
if (__builtin_constant_p (rn)) \
@@ -83,6 +91,7 @@ extern const fenv_t *__fe_mask_env (void) attribute_hidden;
} \
__fr.fenv; \
})
+#endif
/* Like fegetenv_control, but also sets the rounding mode. */
#ifdef _ARCH_PWR9
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