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authorchai <chaifix@163.com>2019-05-11 22:54:56 +0800
committerchai <chaifix@163.com>2019-05-11 22:54:56 +0800
commit9645be0af1b1d5cb0ad5892d5464e1b23c51b550 (patch)
tree129c716bed8e93312421c3adb2f8e7c4f811602d /source/3rd-party/SDL2/src/cpuinfo/SDL_simd.h
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+/*
+ Simple DirectMedia Layer
+ Copyright (C) 1997-2018 Sam Lantinga <slouken@libsdl.org>
+
+ This software is provided 'as-is', without any express or implied
+ warranty. In no event will the authors be held liable for any damages
+ arising from the use of this software.
+
+ Permission is granted to anyone to use this software for any purpose,
+ including commercial applications, and to alter it and redistribute it
+ freely, subject to the following restrictions:
+
+ 1. The origin of this software must not be misrepresented; you must not
+ claim that you wrote the original software. If you use this software
+ in a product, an acknowledgment in the product documentation would be
+ appreciated but is not required.
+ 2. Altered source versions must be plainly marked as such, and must not be
+ misrepresented as being the original software.
+ 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "SDL.h"
+#include "../SDL_internal.h"
+
+/**
+ * \brief Report the alignment this system needs for SIMD allocations.
+ *
+ * This will return the minimum number of bytes to which a pointer must be
+ * aligned to be compatible with SIMD instructions on the current machine.
+ * For example, if the machine supports SSE only, it will return 16, but if
+ * it supports AVX-512F, it'll return 64 (etc). This only reports values for
+ * instruction sets SDL knows about, so if your SDL build doesn't have
+ * SDL_HasAVX512F(), then it might return 16 for the SSE support it sees and
+ * not 64 for the AVX-512 instructions that exist but SDL doesn't know about.
+ * Plan accordingly.
+ */
+extern size_t SDL_SIMDGetAlignment(void);
+
+/**
+ * \brief Allocate memory in a SIMD-friendly way.
+ *
+ * This will allocate a block of memory that is suitable for use with SIMD
+ * instructions. Specifically, it will be properly aligned and padded for
+ * the system's supported vector instructions.
+ *
+ * The memory returned will be padded such that it is safe to read or write
+ * an incomplete vector at the end of the memory block. This can be useful
+ * so you don't have to drop back to a scalar fallback at the end of your
+ * SIMD processing loop to deal with the final elements without overflowing
+ * the allocated buffer.
+ *
+ * You must free this memory with SDL_FreeSIMD(), not free() or SDL_free()
+ * or delete[], etc.
+ *
+ * Note that SDL will only deal with SIMD instruction sets it is aware of;
+ * for example, SDL 2.0.8 knows that SSE wants 16-byte vectors
+ * (SDL_HasSSE()), and AVX2 wants 32 bytes (SDL_HasAVX2()), but doesn't
+ * know that AVX-512 wants 64. To be clear: if you can't decide to use an
+ * instruction set with an SDL_Has*() function, don't use that instruction
+ * set with memory allocated through here.
+ *
+ * SDL_AllocSIMD(0) will return a non-NULL pointer, assuming the system isn't
+ * out of memory.
+ *
+ * \param len The length, in bytes, of the block to allocated. The actual
+ * allocated block might be larger due to padding, etc.
+ * \return Pointer to newly-allocated block, NULL if out of memory.
+ *
+ * \sa SDL_SIMDAlignment
+ * \sa SDL_SIMDFree
+ */
+extern void * SDL_SIMDAlloc(const size_t len);
+
+/**
+ * \brief Deallocate memory obtained from SDL_SIMDAlloc
+ *
+ * It is not valid to use this function on a pointer from anything but
+ * SDL_SIMDAlloc(). It can't be used on pointers from malloc, realloc,
+ * SDL_malloc, memalign, new[], etc.
+ *
+ * However, SDL_SIMDFree(NULL) is a legal no-op.
+ *
+ * \sa SDL_SIMDAlloc
+ */
+extern void SDL_SIMDFree(void *ptr);
+
+/* vi: set ts=4 sw=4 expandtab: */
+