Migrate to using musl libc sprintf family to gain compiled asm.js performance. Keep a copy of handwritten vfprintf and fprintf around to be compatible with the Emscripten filesystem IO library. Also migrate frexp which sprintf depends on to musl libc.

Author: juj

src/library.js

@@ -2838,16 +2838,6 @@ LibraryManager.library = {
     var stdout = {{{ makeGetValue(makeGlobalUse('_stdout'), '0', 'void*') }}};
     return _fprintf(stdout, format, varargs);
   },
-  sprintf__deps: ['snprintf'],
-  sprintf: function(s, format, varargs) {
-    // int sprintf(char *restrict s, const char *restrict format, ...);
-    // http://pubs.opengroup.org/onlinepubs/000095399/functions/printf.html
-    return _snprintf(s, undefined, format, varargs);
-  },
-  asprintf__deps: ['sprintf'],
-  asprintf: function(s, format, varargs) {
-    return _sprintf(-s, format, varargs);
-  },
   dprintf__deps: ['_formatString', 'write'],
   dprintf: function(fd, format, varargs) {
     var result = __formatString(format, varargs);
@@ -2875,22 +2865,10 @@ LibraryManager.library = {
   vfprintf: function(s, f, va_arg) {
     return _fprintf(s, f, {{{ makeGetValue('va_arg', 0, '*') }}});
   },
-  vsnprintf__deps: ['snprintf'],
-  vsnprintf: function(s, n, format, va_arg) {
-    return _snprintf(s, n, format, {{{ makeGetValue('va_arg', 0, '*') }}});
-  },
   vprintf__deps: ['printf'],
   vprintf: function(format, va_arg) {
     return _printf(format, {{{ makeGetValue('va_arg', 0, '*') }}});
   },
-  vsprintf__deps: ['sprintf'],
-  vsprintf: function(s, format, va_arg) {
-    return _sprintf(s, format, {{{ makeGetValue('va_arg', 0, '*') }}});
-  },
-  vasprintf__deps: ['asprintf'],
-  vasprintf: function(s, format, va_arg) {
-    return _asprintf(s, format, {{{ makeGetValue('va_arg', 0, '*') }}});
-  },
   vdprintf__deps: ['dprintf'],
   vdprintf: function (fd, format, va_arg) {
     return _dprintf(fd, format, {{{ makeGetValue('va_arg', 0, '*') }}});
@@ -4500,23 +4478,6 @@ LibraryManager.library = {
     {{{ makeSetValue('intpart', 0, 'Math.floor(x)', 'float') }}};
     return x - {{{ makeGetValue('intpart', 0, 'float') }}};
   },
-  frexp: function(x, exp_addr) {
-    var sig = 0, exp_ = 0;
-    if (x !== 0) {
-      var sign = 1;
-      if (x < 0) {
-        x = -x;
-        sign = -1;
-      }
-      var raw_exp = Math.log(x)/Math.log(2);
-      exp_ = Math.ceil(raw_exp);
-      if (exp_ === raw_exp) exp_ += 1;
-      sig = sign*x/Math.pow(2, exp_);
-    }
-    {{{ makeSetValue('exp_addr', 0, 'exp_', 'i32') }}};
-    return sig;
-  },
-  frexpf: 'frexp',
   finite: function(x) {
     return isFinite(x);
   },

system/lib/libc/musl/src/internal/stdio_impl.h

@@ -95,7 +95,8 @@ int __fmodeflags(const char *);
 FILE *__fopen_rb_ca(const char *, FILE *, unsigned char *, size_t);
 int __fclose_ca(FILE *);
 
-// XXX Emscripten
+// XXX Emscripten: musl-specific vfscanf and vfprintf live parallel to JS handwritten vfscanf and vfprintf, so musl ones are prefixed.
 int MUSL_vfscanf(FILE *restrict f, const char *restrict fmt, va_list ap);
+int MUSL_vfprintf(FILE *restrict f, const char *restrict fmt, va_list ap);
 
 #endif

system/lib/libc/musl/src/math/frexp.c

@@ -0,0 +1,23 @@
+#include <math.h>
+#include <stdint.h>
+
+double frexp(double x, int *e)
+{
+	union { double d; uint64_t i; } y = { x };
+	int ee = y.i>>52 & 0x7ff;
+
+	if (!ee) {
+		if (x) {
+			x = frexp(x*0x1p64, e);
+			*e -= 64;
+		} else *e = 0;
+		return x;
+	} else if (ee == 0x7ff) {
+		return x;
+	}
+
+	*e = ee - 0x3fe;
+	y.i &= 0x800fffffffffffffull;
+	y.i |= 0x3fe0000000000000ull;
+	return y.d;
+}

system/lib/libc/musl/src/math/frexpf.c

@@ -0,0 +1,23 @@
+#include <math.h>
+#include <stdint.h>
+
+float frexpf(float x, int *e)
+{
+	union { float f; uint32_t i; } y = { x };
+	int ee = y.i>>23 & 0xff;
+
+	if (!ee) {
+		if (x) {
+			x = frexpf(x*0x1p64, e);
+			*e -= 64;
+		} else *e = 0;
+		return x;
+	} else if (ee == 0xff) {
+		return x;
+	}
+
+	*e = ee - 0x7e;
+	y.i &= 0x807ffffful;
+	y.i |= 0x3f000000ul;
+	return y.f;
+}

system/lib/libc/musl/src/math/frexpl.c

@@ -0,0 +1,37 @@
+#include <math.h>
+#include <stdint.h>
+#include <float.h>
+
+#if LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384
+
+/* This version is for 80-bit little endian long double */
+
+long double frexpl(long double x, int *e)
+{
+	union { long double ld; uint16_t hw[5]; } y = { x };
+	int ee = y.hw[4]&0x7fff;
+
+	if (!ee) {
+		if (x) {
+			x = frexpl(x*0x1p64, e);
+			*e -= 64;
+		} else *e = 0;
+		return x;
+	} else if (ee == 0x7fff) {
+		return x;
+	}
+
+	*e = ee - 0x3ffe;
+	y.hw[4] &= 0x8000;
+	y.hw[4] |= 0x3ffe;
+	return y.ld;
+}
+
+#else
+
+long double frexpl(long double x, int *e)
+{
+	return frexp(x, e);
+}
+
+#endif

system/lib/libc/musl/src/stdio/asprintf.c

@@ -0,0 +1,13 @@
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdarg.h>
+
+int asprintf(char **s, const char *fmt, ...)
+{
+	int ret;
+	va_list ap;
+	va_start(ap, fmt);
+	ret = vasprintf(s, fmt, ap);
+	va_end(ap);
+	return ret;
+}

system/lib/libc/musl/src/stdio/fwrite.c

@@ -0,0 +1,41 @@
+#include "stdio_impl.h"
+#include <string.h>
+
+size_t __fwritex(const unsigned char *restrict s, size_t l, FILE *restrict f)
+{
+	size_t i=0;
+
+	if (!f->wend && __towrite(f)) return 0;
+
+	if (l > f->wend - f->wpos) return f->write(f, s, l);
+
+	if (f->lbf >= 0) {
+		/* Match /^(.*\n|)/ */
+		for (i=l; i && s[i-1] != '\n'; i--);
+		if (i) {
+			if (f->write(f, s, i) < i)
+				return i;
+			s += i;
+			l -= i;
+		}
+	}
+
+	memcpy(f->wpos, s, l);
+	f->wpos += l;
+	return l+i;
+}
+
+// XXX Emscripten: Not used, since we are not currently using musl file IO.
+#if 0
+size_t fwrite(const void *restrict src, size_t size, size_t nmemb, FILE *restrict f)
+{
+	size_t k, l = size*nmemb;
+	if (!l) return l;
+	FLOCK(f);
+	k = __fwritex(src, l, f);
+	FUNLOCK(f);
+	return k==l ? nmemb : k/size;
+}
+#endif
+
+weak_alias(fwrite, fwrite_unlocked);

system/lib/libc/musl/src/stdio/sprintf.c

@@ -0,0 +1,12 @@
+#include <stdio.h>
+#include <stdarg.h>
+
+int sprintf(char *restrict s, const char *restrict fmt, ...)
+{
+	int ret;
+	va_list ap;
+	va_start(ap, fmt);
+	ret = vsprintf(s, fmt, ap);
+	va_end(ap);
+	return ret;
+}

system/lib/libc/musl/src/stdio/vasprintf.c

@@ -0,0 +1,28 @@
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+
+#define GUESS 240U
+
+int vasprintf(char **s, const char *fmt, va_list ap)
+{
+	va_list ap2;
+	char *a;
+	int l=GUESS;
+
+	if (!(a=malloc(GUESS))) return -1;
+
+	va_copy(ap2, ap);
+	l=vsnprintf(a, GUESS, fmt, ap2);
+	va_end(ap2);
+
+	if (l<GUESS) {
+		char *b = realloc(a, l+1U);
+		*s = b ? b : a;
+		return l;
+	}
+	free(a);
+	if (l<0 || !(*s=malloc(l+1U))) return -1;
+	return vsnprintf(*s, l+1U, fmt, ap);
+}