Mercurial > sdl-ios-xcode
view src/libm/s_scalbn.c @ 3162:dc1eb82ffdaa
Von: Thomas Zimmermann
Betreff: [SDL] [PATCH] Make static variables const
Datum: Tue, 19 May 2009 19:45:37 +0200
Hi,
this is a set of simple changes which make some of SDL's internal static
arrays constant. The purpose is to shrink the number of write-able
static bytes and thus increase the number of memory pages shared between
SDL applications.
The patch set is against trunk@4513. Each of the attached patch files is
specific to a sub-system. The set is completed by a second mail, because
of the list's 40 KiB limit.
The files readelf-r4513.txt and readelf-const-patch.txt where made by
calling 'readelf -S libSDL.so'. They show the difference in ELF sections
without and with the patch. Some numbers measured on my x86-64:
Before
[13] .rodata PROGBITS 00000000000eaaa0 000eaaa0
0000000000008170 0000000000000000 A 0 0 32
[19] .data.rel.ro PROGBITS 00000000003045e0 001045e0
00000000000023d0 0000000000000000 WA 0 0 32
[23] .data PROGBITS 00000000003076e0 001076e0
0000000000004988 0000000000000000 WA 0 0 32
After
[13] .rodata PROGBITS 00000000000eaaa0 000eaaa0
0000000000009a50 0000000000000000 A 0 0 32
[19] .data.rel.ro PROGBITS 0000000000306040 00106040
0000000000002608 0000000000000000 WA 0 0 32
[23] .data PROGBITS 0000000000309360 00109360
0000000000002e88 0000000000000000 WA 0 0 32
The size of the write-able data section decreased considerably. Some
entries became const-after-relocation, while most of its content went
straight into the read-only data section.
Best regards, Thomas
| author | Sam Lantinga <slouken@libsdl.org> |
|---|---|
| date | Wed, 03 Jun 2009 04:37:27 +0000 |
| parents | a98604b691c8 |
| children | 9ac6f0782dd6 |
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/* @(#)s_scalbn.c 5.1 93/09/24 */ /* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunPro, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ #if defined(LIBM_SCCS) && !defined(lint) static const char rcsid[] = "$NetBSD: s_scalbn.c,v 1.8 1995/05/10 20:48:08 jtc Exp $"; #endif /* * scalbn (double x, int n) * scalbn(x,n) returns x* 2**n computed by exponent * manipulation rather than by actually performing an * exponentiation or a multiplication. */ #include "math.h" #include "math_private.h" libm_hidden_proto(copysign) #ifdef __STDC__ static const double #else static double #endif two54 = 1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */ twom54 = 5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */ huge = 1.0e+300, tiny = 1.0e-300; libm_hidden_proto(scalbn) #ifdef __STDC__ double scalbn(double x, int n) #else double scalbn(x, n) double x; int n; #endif { int32_t k, hx, lx; EXTRACT_WORDS(hx, lx, x); k = (hx & 0x7ff00000) >> 20; /* extract exponent */ if (k == 0) { /* 0 or subnormal x */ if ((lx | (hx & 0x7fffffff)) == 0) return x; /* +-0 */ x *= two54; GET_HIGH_WORD(hx, x); k = ((hx & 0x7ff00000) >> 20) - 54; if (n < -50000) return tiny * x; /*underflow */ } if (k == 0x7ff) return x + x; /* NaN or Inf */ k = k + n; if (k > 0x7fe) return huge * copysign(huge, x); /* overflow */ if (k > 0) { /* normal result */ SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20)); return x; } if (k <= -54) { if (n > 50000) /* in case integer overflow in n+k */ return huge * copysign(huge, x); /*overflow */ else return tiny * copysign(tiny, x); /*underflow */ } k += 54; /* subnormal result */ SET_HIGH_WORD(x, (hx & 0x800fffff) | (k << 20)); return x * twom54; } libm_hidden_def(scalbn)