x86: Use default libc_fe* implementation for float128
Commit Message
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(-)
@@ -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