From a1805f7bb9bc97b8267642d9d6458dd7edfac12a Mon Sep 17 00:00:00 2001 From: David Schultz Date: Sat, 17 Jan 2009 18:57:12 +0000 Subject: When f[w]printf() is called on an unbuffered file like stdout, it sets up a fake buffered FILE and then effectively calls itself recursively. Unfortunately, gcc doesn't know how to do tail call elimination in this case, and actually makes things worse by inlining __sbprintf(). This means that f[w]printf() to stderr was allocating about 5k of stack on 64-bit platforms, much of which was never used. I've reorganized things to eliminate the waste. In addition to saving some stack space, this improves performance in my tests by anywhere from 5% to 17% (depending on the test) when -fstack-protector is enabled. I found no statistically significant performance difference when stack protection is turned off. (The tests redirected stderr to /dev/null.) --- lib/libc/stdio/vfwprintf.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-) (limited to 'lib/libc/stdio/vfwprintf.c') diff --git a/lib/libc/stdio/vfwprintf.c b/lib/libc/stdio/vfwprintf.c index 2a577b28cc66..937134cb6cf7 100644 --- a/lib/libc/stdio/vfwprintf.c +++ b/lib/libc/stdio/vfwprintf.c @@ -67,7 +67,7 @@ __FBSDID("$FreeBSD$"); #include "printflocal.h" static int __sprint(FILE *, struct __suio *); -static int __sbprintf(FILE *, const wchar_t *, va_list); +static int __sbprintf(FILE *, const wchar_t *, va_list) __noinline; static wint_t __xfputwc(wchar_t, FILE *); static wchar_t *__mbsconv(char *, int); @@ -114,6 +114,10 @@ __sbprintf(FILE *fp, const wchar_t *fmt, va_list ap) FILE fake; unsigned char buf[BUFSIZ]; + /* XXX This is probably not needed. */ + if (prepwrite(fp) != 0) + return (EOF); + /* copy the important variables */ fake._flags = fp->_flags & ~__SNBF; fake._file = fp->_file; @@ -250,7 +254,12 @@ vfwprintf(FILE * __restrict fp, const wchar_t * __restrict fmt0, va_list ap) int ret; FLOCKFILE(fp); - ret = __vfwprintf(fp, fmt0, ap); + /* optimise fprintf(stderr) (and other unbuffered Unix files) */ + if ((fp->_flags & (__SNBF|__SWR|__SRW)) == (__SNBF|__SWR) && + fp->_file >= 0) + ret = __sbprintf(fp, fmt0, ap); + else + ret = __vfwprintf(fp, fmt0, ap); FUNLOCKFILE(fp); return (ret); } @@ -419,11 +428,6 @@ __vfwprintf(FILE *fp, const wchar_t *fmt0, va_list ap) if (prepwrite(fp) != 0) return (EOF); - /* optimise fprintf(stderr) (and other unbuffered Unix files) */ - if ((fp->_flags & (__SNBF|__SWR|__SRW)) == (__SNBF|__SWR) && - fp->_file >= 0) - return (__sbprintf(fp, fmt0, ap)); - thousands_sep = '\0'; grouping = NULL; convbuf = NULL; -- cgit v1.2.3