aph pointed out that signals make a mess of my idea of writing below r1 and protecting later, but I realised that you know in advance how much stack a method will use so you can just set up the stack for that before you call it. Of course, all that has to be in assembler, so I can’t use my funky StackFrame class :( I decided it’s high time I made a table of register usage across ABIs to aid me in writing this:
| ppc | ppc64 | |
|---|---|---|
r0 |
Volatile register which may be modified during function linkage | |
r1 |
Stack frame pointer | |
r2 |
Reserved | TOC pointer |
r3 |
Volatile registers used for parameter-passing and return values | |
r4 |
||
r5-r10 |
Volatile registers used for parameter-passing | |
r11 |
Volatile registers which may be modified during function linkage | Volatile register used in calls by pointer and/or as an environment pointer |
r12 |
Volatile register used in function linkage and exception handling | |
r13 |
Small data area pointer | System thread ID |
r14-r30 |
Non-volatile registers used for local variables | |
r31 |
Non-volatile register used for local variables or as an environment pointer | |
