Specifically inalphablit_alpha_sse2_argb_no_surf_alpha_opaque_dst

I found an opportunity to reduce the amount of CPU clocks / instructions needed to move the alpha component from the src pixels into an interleaved 16 bit format.

In my testing, this got 10k 512x512 alpha blits (of this format) from around 2 seconds to around 1.6 seconds, a 15-20% improvement.

importpygameimporttimepygame.init()screen=pygame.Surface((1920,1080),depth=32)screen.fill((255,0,23))surf=pygame.Surface((512,512),pygame.SRCALPHA)surf.fill((22,156,77,192))print(screen,surf)start=time.time()for_inrange(10000):screen.blit(surf, (51,67))print(time.time()-start)

This is my test program. Note that the "screen" surface has a bit depth of 32 but does not have per pixel alpha.