问题
I'm porting some ARM NEON code to 64-bit ARM-v8, but I can't find a good documentation about it.
Many features seems to be gone, and I don't know how to implement the same function without using them.
So, the general question is: where can I find a complete reference for the new SIMD implementation, including explanation of how to do the same simple tasks which are explained in the many ARM-NEON tutorials?
Some questions about particular features:
1 - How do I load a value in all the lane of a Dx register? The old code was
mov R0, #42
vdup.8 D0, R0
My guess is:
mov W0, #42
dup V0.8B, W0
2 - How do I load multiple Dx/Qx registers with interleaved data? In the old code this was:
vld4.8 {D0-D3}, [R0]!
But I can't find anything in the new docs.
I understand it's a completely new model, but it's not very well-documented (or at least, I'm unable to find any reference with readable samples)
回答1:
The documentation on using ARMv8 in Android is not very good, but for your specific questions, they're answered quite well in this document:
ARMv8 Instruction Set Overview
To answer your specific questions:
mov R0, #42
vdup.8 D0, R0
becomes
mov w0,#42
dup v0.8b,w0
and
vld4.8 {d0-d3}, [r0]!
becomes
ld4 {v0.8b,v1.8b,v2.8b,v3.8b},[x0],#32
来源：https://stackoverflow.com/questions/28050300/porting-arm-neon-code-to-aarch64-many-questions