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7a069cc4b0
Modern C runtimes have well optimized memset and memcpy, so use those instead of dispatching into SDL's versions. In addition, some compilers can analyze memset and memcpy calls and directly turn them into optimized assembly.
137 lines
3.9 KiB
C
137 lines
3.9 KiB
C
/*
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Simple DirectMedia Layer
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Copyright (C) 1997-2024 Sam Lantinga <slouken@libsdl.org>
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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*/
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#include "SDL_internal.h"
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#ifdef SDL_memset
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#undef SDL_memset
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#endif
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#if SDL_DYNAMIC_API
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#define SDL_memset SDL_memset_REAL
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#endif
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void *SDL_memset(SDL_OUT_BYTECAP(len) void *dst, int c, size_t len)
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{
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#ifdef __GNUC__
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return __builtin_memset(dst, c, len);
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#elif defined(HAVE_MEMSET)
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return memset(dst, c, len);
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#else
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size_t left;
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Uint32 *dstp4;
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Uint8 *dstp1 = (Uint8 *)dst;
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Uint8 value1;
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Uint32 value4;
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/* The value used in memset() is a byte, passed as an int */
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c &= 0xff;
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/* The destination pointer needs to be aligned on a 4-byte boundary to
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* execute a 32-bit set. Set first bytes manually if needed until it is
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* aligned. */
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value1 = (Uint8)c;
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while ((uintptr_t)dstp1 & 0x3) {
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if (len--) {
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*dstp1++ = value1;
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} else {
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return dst;
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}
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}
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value4 = ((Uint32)c | ((Uint32)c << 8) | ((Uint32)c << 16) | ((Uint32)c << 24));
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dstp4 = (Uint32 *)dstp1;
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left = (len % 4);
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len /= 4;
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while (len--) {
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*dstp4++ = value4;
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}
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dstp1 = (Uint8 *)dstp4;
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switch (left) {
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case 3:
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*dstp1++ = value1;
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case 2:
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*dstp1++ = value1;
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case 1:
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*dstp1++ = value1;
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}
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return dst;
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#endif /* HAVE_MEMSET */
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}
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/* Note that memset() is a byte assignment and this is a 32-bit assignment, so they're not directly equivalent. */
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void *SDL_memset4(void *dst, Uint32 val, size_t dwords)
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{
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#if defined(__APPLE__) && defined(HAVE_STRING_H)
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memset_pattern4(dst, &val, dwords * 4);
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#elif defined(__GNUC__) && defined(__i386__)
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int u0, u1, u2;
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__asm__ __volatile__(
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"cld \n\t"
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"rep ; stosl \n\t"
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: "=&D"(u0), "=&a"(u1), "=&c"(u2)
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: "0"(dst), "1"(val), "2"(SDL_static_cast(Uint32, dwords))
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: "memory");
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#else
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size_t _n = (dwords + 3) / 4;
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Uint32 *_p = SDL_static_cast(Uint32 *, dst);
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Uint32 _val = (val);
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if (dwords == 0) {
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return dst;
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}
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switch (dwords % 4) {
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case 0:
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do {
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*_p++ = _val;
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SDL_FALLTHROUGH;
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case 3:
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*_p++ = _val;
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SDL_FALLTHROUGH;
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case 2:
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*_p++ = _val;
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SDL_FALLTHROUGH;
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case 1:
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*_p++ = _val;
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} while (--_n);
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}
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#endif
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return dst;
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}
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/* The optimizer on Visual Studio 2005 and later generates memcpy() and memset() calls.
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Always provide it for the SDL3 DLL, but skip it when building static lib w/ static runtime. */
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#if defined(_MSC_VER) && (_MSC_VER >= 1400) && (!defined(_MT) || defined(DLL_EXPORT))
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/* NOLINTNEXTLINE(readability-redundant-declaration) */
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extern void *memset(void *dst, int c, size_t len);
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#ifndef __INTEL_LLVM_COMPILER
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#pragma intrinsic(memset)
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#endif
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#ifndef __clang__
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#pragma function(memset)
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#endif
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/* NOLINTNEXTLINE(readability-inconsistent-declaration-parameter-name) */
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void *memset(void *dst, int c, size_t len)
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{
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return SDL_memset(dst, c, len);
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}
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#endif /* (_MSC_VER >= 1400) && (!defined(_MT) || defined(DLL_EXPORT)) */
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