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Re: improve printf locality

Minor change. Please use another name for the cvt value type rather than _DOUBLE (i.e. I don't like the idea of defining _DOUBLE as _LONG_DOUBLE). Suggest something like _CVT_VALUE_FLOAT_TYPE. Other than that, patch is fine.

-- Jeff J.

Eric Blake wrote:
Eric Blake <ebb9 <at> byu.net> writes:

On cygwin, where newlib is configured with --enable-newlib-io-long-double,
print consumed more than an entire page of virtual memory in stack space!
 This causes unnecessary page faults, decreased cache locality, and other
potential slowdowns.  It was because at one point in history, newlib used
to stack allocate the worst case length for %Lf output (if you have a
128-bit long double with a 15 bit exponent, this can result in more than
4900 characters).  But now newlib uses struct _reent to manage %f output,
so the storage claimed by buf[BUF] was 90% unused.

Resubmit, in light of other patches committed in the meantime. OK to apply?


2007-05-10 Eric Blake <ebb9@byu.net>

	* libc/stdio/vfprintf.c (_VFPRINTF_R): Fix use of decimal point
	in %f.  Avoid malloc when possible for %S.
	(BUF): Improve stack locality by using smaller size.
	(MAXEXPLEN): Define.
	(exponent): Use smaller stack size.

Index: libc/stdio/vfprintf.c
===================================================================
RCS file: /cvs/src/src/newlib/libc/stdio/vfprintf.c,v
retrieving revision 1.58
diff -u -p -r1.58 vfprintf.c
--- libc/stdio/vfprintf.c 11 May 2007 20:09:00 -0000 1.58
+++ libc/stdio/vfprintf.c 14 May 2007 18:08:41 -0000
@@ -224,43 +224,66 @@ _DEFUN(__sbprintf, (rptr, fp, fmt, ap),
#ifdef FLOATING_POINT
-#include <locale.h>
-#include <math.h>
-#include "floatio.h"
+# include <locale.h>
+# include <math.h>
-#if ((MAXEXP+MAXFRACT+1) > MB_LEN_MAX)
-# define BUF (MAXEXP+MAXFRACT+1) /* + decimal point */
-#else -# define BUF MB_LEN_MAX
-#endif
+/* For %La, an exponent of 15 bits occupies the exponent character, a
+ sign, and up to 5 digits. */
+# define MAXEXPLEN 7
+# define DEFPREC 6
-#define DEFPREC 6
+# ifdef _NO_LONGDBL
+
+extern char *_dtoa_r _PARAMS((struct _reent *, double, int,
+ int, int *, int *, char **));
+
+# define _DOUBLE double
+# define _DTOA_R _dtoa_r
+# define FREXP frexp
+
+# else /* !_NO_LONGDBL */
+
+extern char *_ldtoa_r _PARAMS((struct _reent *, _LONG_DOUBLE, int,
+ int, int *, int *, char **));
-#ifdef _NO_LONGDBL
-static char *
-_EXFUN(cvt, (struct _reent *, double, int, int, char *, int *, int, int *,
- char *));
-#else
-static char *
-_EXFUN(cvt, (struct _reent *, _LONG_DOUBLE, int, int, char *, int *, int,
- int *, char *));
extern int _EXFUN(_ldcheck,(_LONG_DOUBLE *));
-#endif
-static int _EXFUN(exponent, (char *, int, int));
+# define _DOUBLE _LONG_DOUBLE
+# define _DTOA_R _ldtoa_r
+/* FIXME - frexpl is not yet supported; and cvt infloops if (double)f
+ converts a finite value into infinity. */
+/* # define FREXP frexpl */
+# define FREXP(f,e) ((_LONG_DOUBLE) frexp ((double)f, e))
+# endif /* !_NO_LONGDBL */
-#else /* no FLOATING_POINT */
+static char *cvt(struct _reent *, _DOUBLE, int, int, char *, int *, int, int *,
+ char *);
-#define BUF 40
+static int exponent(char *, int, int);
#endif /* FLOATING_POINT */
+/* BUF must be big enough for the maximum %#llo (assuming long long is
+ at most 64 bits, this would be 23 characters), the maximum
+ multibyte character %C, and the maximum precision of %La (assuming
+ long double is at most 128 bits with 113 bits of mantissa, this
+ would be 29 characters). %e, %f, and %g use reentrant storage
+ shared with mprec. All other formats that use buf get by with
+ fewer characters. Making BUF slightly bigger reduces the need for
+ malloc in %a and %S, when large precision or long strings are
+ processed. */
+#define BUF 40
+#if defined _MB_CAPABLE && MB_LEN_MAX > BUF
+# undef BUF
+# define BUF MB_LEN_MAX
+#endif
+
#ifndef _NO_LONGLONG
-#define quad_t long long
-#define u_quad_t unsigned long long
+# define quad_t long long
+# define u_quad_t unsigned long long
#else
-#define quad_t long
-#define u_quad_t unsigned long
+# define quad_t long
+# define u_quad_t unsigned long
#endif
typedef quad_t * quad_ptr_t;
@@ -389,8 +412,8 @@ _DEFUN(_VFPRINTF_R, (data, fp, fmt0, ap)
int expt; /* integer value of exponent */
int expsize = 0; /* character count for expstr */
int ndig = 0; /* actual number of digits returned by cvt */
- char expstr[7]; /* buffer for exponent string */
-#endif
+ char expstr[MAXEXPLEN]; /* buffer for exponent string */
+#endif /* FLOATING_POINT */
u_quad_t _uquad; /* integer arguments %[diouxX] */
enum { OCT, DEC, HEX } base;/* base for [diouxX] conversion */
int dprec; /* a copy of prec if [diouxX], 0 otherwise */
@@ -400,7 +423,7 @@ _DEFUN(_VFPRINTF_R, (data, fp, fmt0, ap)
#define NIOV 8
struct __suio uio; /* output information: summary */
struct __siov iov[NIOV];/* ... and individual io vectors */
- char buf[BUF]; /* space for %c, %[diouxX], %[eEfgG] */
+ char buf[BUF]; /* space for %c, %S, %[diouxX], %[aA] */
char ox[2]; /* space for 0x hex-prefix */
#ifdef _MB_CAPABLE
wchar_t wc;
@@ -1030,8 +1053,8 @@ reswitch: switch (ch) {
while (1) {
if (wcp[m] == L'\0')
break;
- if ((n = (int)_wcrtomb_r (data, - buf, wcp[m], &ps)) == -1) {
+ if ((n = (int)_wcrtomb_r (data,
+ buf, wcp[m], &ps)) == -1) {
fp->_flags |= __SERR;
goto error;
}
@@ -1044,31 +1067,35 @@ reswitch: switch (ch) {
}
}
else {
- if ((size = (int)_wcsrtombs_r (data, - NULL, &wcp, 0, &ps)) == -1) {
+ if ((size = (int)_wcsrtombs_r (data,
+ NULL, &wcp, 0, &ps)) == -1) {
fp->_flags |= __SERR;
goto error;
}
wcp = (_CONST wchar_t *)cp;
}
- +
if (size == 0)
break;
- - if ((malloc_buf = - (char *)_malloc_r (data, size + 1)) == NULL) {
- fp->_flags |= __SERR;
- goto error;
- }
- +
+ if (size >= BUF) {
+ if ((malloc_buf =
+ (char *)_malloc_r (data, size + 1))
+ == NULL) {
+ fp->_flags |= __SERR;
+ goto error;
+ }
+ cp = malloc_buf;
+ } else
+ cp = buf;
+
/* Convert widechar string to multibyte string. */
memset ((_PTR)&ps, '\0', sizeof (mbstate_t));
- if (_wcsrtombs_r (data, malloc_buf, - &wcp, size, &ps) != size) {
+ if (_wcsrtombs_r (data, malloc_buf,
+ &wcp, size, &ps) != size) {
fp->_flags |= __SERR;
goto error;
}
- cp = malloc_buf;
cp[size] = '\0';
}
#endif /* _MB_CAPABLE */
@@ -1254,11 +1281,11 @@ number: if ((dprec = prec) >= 0)
PRINT (cp, ndig);
PAD (expt - ndig, zeroes);
if (flags & ALT)
- PRINT (".", 1);
+ PRINT (decimal_point, 1);
} else {
PRINT (cp, expt);
cp += expt;
- PRINT (".", 1);
+ PRINT (decimal_point, 1);
PRINT (cp, ndig - expt);
}
} else { /* 'a', 'A', 'e', or 'E' */
@@ -1305,21 +1332,6 @@ error:
#ifdef FLOATING_POINT
-# ifdef _NO_LONGDBL
-extern char *_dtoa_r _PARAMS((struct _reent *, double, int,
- int, int *, int *, char **));
-# define _DTOA_R _dtoa_r
-# define FREXP frexp
-# else
-extern char *_ldtoa_r _PARAMS((struct _reent *, _LONG_DOUBLE, int,
- int, int *, int *, char **));
-# define _DTOA_R _ldtoa_r
-/* FIXME - frexpl is not yet supported; and cvt infloops if (double)f
- converts a finite value into infinity. */
-/* # define FREXP frexpl */
-# define FREXP(f,e) ((_LONG_DOUBLE) frexp ((double)f, e))
-# endif
-
/* Using reentrant DATA, convert finite VALUE into a string of digits
with no decimal point, using NDIGITS precision and FLAGS as guides
to whether trailing zeros must be included. Set *SIGN to nonzero
@@ -1327,31 +1339,9 @@ extern char *_ldtoa_r _PARAMS((struct _r
*LENGTH to the length of the returned string. CH must be one of
[aAeEfFgG]; if it is [aA], then the return string lives in BUF,
otherwise the return value shares the mprec reentrant storage. */
-# ifdef _NO_LONGDBL
static char *
-_DEFUN(cvt, (data, value, ndigits, flags, sign, decpt, ch, length, buf),
- struct _reent *data _AND
- double value _AND
- int ndigits _AND
- int flags _AND
- char *sign _AND
- int *decpt _AND
- int ch _AND
- int *length _AND
- char *buf)
-# else
-static char *
-_DEFUN(cvt, (data, value, ndigits, flags, sign, decpt, ch, length, buf),
- struct _reent *data _AND
- _LONG_DOUBLE value _AND
- int ndigits _AND
- int flags _AND
- char *sign _AND
- int *decpt _AND
- int ch _AND
- int *length _AND
- char *buf)
-# endif
+cvt(struct _reent *data, _DOUBLE value, int ndigits, int flags, char *sign,
+ int *decpt, int ch, int *length, char *buf)
{
int mode, dsgn;
char *digits, *bp, *rve;
@@ -1444,13 +1434,10 @@ _DEFUN(cvt, (data, value, ndigits, flags
}
static int
-_DEFUN(exponent, (p0, exp, fmtch),
- char *p0 _AND
- int exp _AND
- int fmtch)
+exponent(char *p0, int exp, int fmtch)
{
register char *p, *t;
- char expbuf[10];
+ char expbuf[MAXEXPLEN];
# ifdef _WANT_IO_C99_FORMATS
int isa = fmtch == 'a' || fmtch == 'A';
# else
@@ -1465,13 +1452,13 @@ _DEFUN(exponent, (p0, exp, fmtch),
}
else
*p++ = '+';
- t = expbuf + 10;
+ t = expbuf + MAXEXPLEN;
if (exp > 9) {
do {
*--t = to_char (exp % 10);
} while ((exp /= 10) > 9);
*--t = to_char (exp);
- for (; t < expbuf + 10; *p++ = *t++);
+ for (; t < expbuf + MAXEXPLEN; *p++ = *t++);
}
else {
if (!isa)



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