DavidSpickett wrote:
> Arm M profile has
> https://developer.arm.com/Architectures/Arm%20Custom%20Instructions, I'll
> look into that and see if it would benefit from a change of output format
> too. Just in theory though, I don't think we shipped support for open source
> debuggers and I'm not about to implement it myself.
CDE works by assigning one of the co-processors to be the encodings for the
custom instructions and it has a few fixed formats you can use. It's not like
RISC-V where the layout can be anything you want. Which means that the
disassembler would probably print some form, with encoding, and that can
already be used to filter if you wanted to.
I also checked how AArch64 works:
``
$ cat /tmp/test.c
int main() {
asm volatile(".inst 0x43214444");
return 0;
}
```
objdump shows the bytes:
```
0000000000000714 <main>:
714: d10043ff sub sp, sp, #0x10
718: 2a1f03e0 mov w0, wzr
71c: b9000fff str wzr, [sp, #0xc]
720: 43214444 <unknown>
724: 910043ff add sp, sp, #0x10
728: d65f03c0 ret
```
As does LLDB:
```
(lldb) dis -b
test.o`main:
0xaaaaaaaaa714 <+0>: 0xd10043ff sub sp, sp, #0x10
0xaaaaaaaaa718 <+4>: 0x2a1f03e0 mov w0, wzr
0xaaaaaaaaa71c <+8>: 0xb9000fff str wzr, [sp, #0xc]
-> 0xaaaaaaaaa720 <+12>: 0x43214444 ;
unknown opcode
0xaaaaaaaaa724 <+16>: 0x910043ff add sp, sp, #0x10
0xaaaaaaaaa728 <+20>: 0xd65f03c0 ret
```
So for AArch64 we happen to mostly match objdump's output, and it's useful
enough for humans and scripts because it can only ever be 32-bit encodings.
Also having looked at the pretty printer system in llvm-objdump, I think `if
riscv` is ok here. LLDB is effectively a selective objdumper and the only
difference between what you're adding here and what llvm-objdump has is the
framework around it. Which we do not need when only RISC-V wants this.
https://github.com/llvm/llvm-project/pull/145793
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