(This is the legacy documentation for SDL2, the previous stable version; SDL3 is the current stable version.)

SDL_SIMDAlloc

Allocate memory in a SIMD-friendly way.

Header File

Syntax

void * SDL_SIMDAlloc(const size_t len);

Function Parameters

const size_t

len

The length, in bytes, of the block to allocate. The actual allocated block might be larger due to padding, etc.

Return Value

(void *) Returns a pointer to the newly-allocated block, NULL if out of memory.

Remarks

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, but you are not allowed to dereference it (because you only own zero bytes of that buffer).

Version

This function is available since SDL 2.0.10.