tree 1508802084c4d934166494f3a5b9a06db2d9dc00
parent 50d1a4aa725fbc78ee89ffde5e83b4ee4fe4893e
author Clement Courbet <courbet@google.com> 1578384504 +0100
committer Clement Courbet <courbet@google.com> 1578413076 +0100

Avoid reloads in vp9_read_mode_info.

The compiler cannot prove that the buffers do not alias, so it has to emit a
reload. On our internal workloads, the reloads are about 1% of the total time
spent decoding frames.

The loop before the change:

movzwl 0x8(%r15), %edx       # load ref_frame
addq $0xc, %rax
movw %dx, -0x4(%rax)         # store ref_frame
movq 0xc(%r15), %rdx         # load mv
movq %rdx, -0xc(%rax)        # store mv
cmpq %rax, %rcx
jne -0x1a

The loop after the change:

movw %r9w, 0x8(%rax)         # store cached ref_frame
addq $0xc, %rax
movq %r8, -0xc(%rax)         # store cached mv
cmpq %rax, %rdx
jne -0x12

Change-Id: Ia1e9634bcabb4d7e06ed60f470bc4cd67f5ab27e