问题
There is a similar post that covers regular registers. What about NEON registers. As far as I remember either top half or bottom half of registers have to be preserved across function calls. I can't find that info anywhere, can somebody clarify that?
thanks
From the AAPCS, §5.1.1 Core registers:
- r0-r3 are the argument and scratch registers; r0-r1 are also the result registers
- r4-r8 are callee-save registers
- r9 might be a callee-save register or not (on some variants of AAPCS it is a special register)
- r10-r11 are callee-save registers
- r12-r15 are special registers
From the AAPCS, §5.1.2.1 VFP register usage conventions (VFP v2, v3 and the Advanced SIMD Extension):
- s16–s31 (d8–d15, q4–q7) must be preserved
- s0–s15 (d0–d7, q0–q3) and d16–d31 (q8–q15) do not need to be preserved
回答1:
From the AAPCS, §5.1.2.1:
- s16–s31 (d8–d15, q4–q7) must be preserved
- s0–s15 (d0–d7, q0–q3) and d16–d31 (q8–q15) do not need to be preserved
来源：https://stackoverflow.com/questions/5288390/arm-to-c-calling-convention-neon-registers-to-save