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Use STRFMON_LDBL_IS_DBL instead of __ldbl_is_dbl.

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On platforms where long double used to have the same format as double,
but later switched to a different format (alpha, s390, sparc, and
powerpc), accessing the older behavior is possible and it happens via
__nldbl_* functions (not on the API, but accessible from header
redirection and from compat symbols).  These functions write to the
global flag __ldbl_is_dbl, which tells other functions that long double
variables should be handled as double.  This patch takes the first step
towards removing this global flag and creates __vstrfmon_l_internal,
which takes an explicit flags parameter.

This change arguably makes the generated code slightly worse on
architectures where __ldbl_is_dbl is never true; right now, on those
architectures, it's a compile-time constant; after this change, the
compiler could theoretically prove that __vstrfmon_l_internal was
never called with a nonzero flags argument, but it would probably need
LTO to do it.  This is not performance critical code and I tend to
think that the maintainability benefits of removing action at a
distance are worth it.  However, we _could_ wrap the runtime flag
check with a macro that was defined to ignore its argument and always
return false on architectures where __ldbl_is_dbl is never true, if
people think the codegen benefits are important.

Tested for powerpc and powerpc64le.
This commit is contained in:
Zack Weinberg
2018-03-07 14:31:57 -05:00
committed by Gabriel F. T. Gomes
parent 346ef23f19
commit c75772e3f0
7 changed files with 67 additions and 37 deletions
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8
stdlib/strfmon_l.c
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@ -76,8 +76,8 @@
too. Some of the information contradicts the information which can
be specified in format string. */
ssize_t
__vstrfmon_l (char *s, size_t maxsize, locale_t loc, const char *format,
va_list ap)
__vstrfmon_l_internal (char *s, size_t maxsize, locale_t loc,
const char *format, va_list ap, unsigned int flags)
{
struct __locale_data *current = loc->__locales[LC_MONETARY];
_IO_strfile f;
@ -268,7 +268,7 @@ __vstrfmon_l (char *s, size_t maxsize, locale_t loc, const char *format,
if (*fmt == 'L')
{
++fmt;
if (!__ldbl_is_dbl)
if (__glibc_likely ((flags & STRFMON_LDBL_IS_DBL) == 0))
is_long_double = 1;
}
@ -608,7 +608,7 @@ ___strfmon_l (char *s, size_t maxsize, locale_t loc, const char *format, ...)
va_start (ap, format);
ssize_t res = __vstrfmon_l (s, maxsize, loc, format, ap);
ssize_t res = __vstrfmon_l_internal (s, maxsize, loc, format, ap, 0);
va_end (ap);