diff mbox series

x86: Use default libc_fe* implementation for float128

Message ID 20200420185651.944-1-adhemerval.zanella@linaro.org
State New
Headers show
Series x86: Use default libc_fe* implementation for float128 | expand

Commit Message

Adhemerval Zanella April 20, 2020, 6:56 p.m. UTC
The exported x86_64 fenv.h functions operate on both i387 and SSE (since
they should work on both float, double, and long double) while the
internal libc_fe* set either SSE (float, double, and float128) or
i387 (long double).

The rounding mode is used by soft-fp (libgcc and glibc), so that must be
set for float128 computations.  For x86_64 it uses SSE mode, while for
i386 is uses x87.

However for exception generation both 387 and SSE exception might
be generated even for x86_64.  The FP_EX_DIVZERO, FP_EX_DIVZERO, and
FP_EX_INEXACT uses SSE while FP_EX_DENORM, FP_EX_OVERFLOW, and
FP_EX_UNDERFLOW uses x87.

For i686 it depends whether libgcc was built for SSE math (where it
follows x86_64 behaviour) or x87 math (which uses only x87 mode).

In any case use generic routines to handle float128 since it handles
both modes.  It allows to use libc_fe* macros on float128 implementation
for x86_64.

I checked on top of the libc_fe* optimization patchset for float128 [1]
(which can be checked on my branch [2]) on both x86_64-linux-gnu and
i686-linux-gnu.

[1] https://sourceware.org/pipermail/libc-alpha/2020-March/112121.html
[2] https://sourceware.org/git/?p=glibc.git;a=shortlog;h=refs/heads/azanella/x86-libc_fe

Checked on x86_64-linux-gnu.
---
 sysdeps/x86/fpu/fenv_private.h | 44 +++++++++++++++++-----------------
 1 file changed, 22 insertions(+), 22 deletions(-)
diff mbox series

Patch

diff --git a/sysdeps/x86/fpu/fenv_private.h b/sysdeps/x86/fpu/fenv_private.h
index 8453aaa270..032bbd0dfa 100644
--- a/sysdeps/x86/fpu/fenv_private.h
+++ b/sysdeps/x86/fpu/fenv_private.h
@@ -293,28 +293,28 @@  libc_feresetround_387 (fenv_t *e)
 # define libc_feholdsetround_53bit	libc_feholdsetround_387_53bit
 #endif
 
-#ifdef __x86_64__
-/* The SSE rounding mode is used by soft-fp (libgcc and glibc) on
-   x86_64, so that must be set for float128 computations.  */
-# define SET_RESTORE_ROUNDF128(RM) \
-  SET_RESTORE_ROUND_GENERIC (RM, libc_feholdsetround_sse, libc_feresetround_sse)
-# define libc_feholdexcept_setroundf128	libc_feholdexcept_setround_sse
-# define libc_feupdateenv_testf128	libc_feupdateenv_test_sse
-# define libc_feholdexceptf128	libc_feholdexcept_sse
-# define libc_fesetenvf128	libc_fesetenv_sse
-# define libc_feupdateenvf128	libc_feupdateenv_sse
-# define libc_fesetroundf128	libc_fesetround_sse
-#else
-/* The 387 rounding mode is used by soft-fp for 32-bit, but whether
-   387 or SSE exceptions are used depends on whether libgcc was built
-   for SSE math, which is not known when glibc is being built.  */
-# define libc_feholdexcept_setroundf128	default_libc_feholdexcept_setround
-# define libc_feupdateenv_testf128	default_libc_feupdateenv_test
-# define libc_feholdexceptf128	default_libc_feholdexcept
-# define libc_fesetenvf128	default_libc_fesetenv
-# define libc_feupdateenvf128	default_libc_feupdateenv
-# define libc_fesetroundf128	default_libc_fesetround
-#endif
+/* The rounding mode is used by soft-fp (libgcc and glibc), so that must be
+   set for float128 computations.  For x86_64 it uses SSE mode, while for
+   i386 is uses x87.
+
+   However for exception generation both 387 and SSE exception might be
+   generated even for x86_64: FP_EX_DIVZERO, FP_EX_DIVZERO, and FP_EX_INEXACT
+   uses SSE while FP_EX_DENORM, FP_EX_OVERFLOW, and FP_EX_UNDERFLOW uses x87.
+
+   For i686 it depends whether libgcc was built for SSE math (where it
+   follows x86_64 behaviour) or x87 math (which uses only x87 mode).
+
+   In any case use generic routines to handle float128 since it handles
+   both modes.  */
+#define SET_RESTORE_ROUNDF128(RM) \
+  SET_RESTORE_ROUND_GENERIC (RM, default_libc_feholdsetround, \
+				 default_libc_feresetround)
+#define libc_feholdexcept_setroundf128	default_libc_feholdexcept_setround
+#define libc_feupdateenv_testf128	default_libc_feupdateenv_test
+#define libc_feholdexceptf128		default_libc_feholdexcept
+#define libc_fesetenvf128		default_libc_fesetenv
+#define libc_feupdateenvf128		default_libc_feupdateenv
+#define libc_fesetroundf128		default_libc_fesetround
 
 /* We have support for rounding mode context.  */
 #define HAVE_RM_CTX 1