I've been using godbolt.org to figure out which #AArch64 instructions are generated for which operations, as I find the instruction descriptions are frequently baffling.

But I've been reduced to taking the godbolt 8 bit hex instructions and compare them against the 2000 #AArch64 instructions to get a match (yes, the mnemonic helps a lot, but as many mnemonics have multiple encodings, it's back to tedium). It's laborious because the instruction encodings do not line up on byte boundaries, so I have to convert it to binary and then mark out the bit fields by hand (dammit D needs bit fields!)

I finally realized disasmarm.d can help. I fixed it so one just types in the 8 hex bytes on the command for the instruction, and it will disassemble it and provide the correct URL to the manual page for that instruction.

disasmarm.d can be compiled with:

```
dmd disasmarm.d -version=StandAlone
```

to make a standalone program and it will do a little disassembling:

```
./disasmarm fd401bff
FD 40 1B FF  ldr d31,[sp,#0x30] // https://www.scs.stanford.edu/~zyedidia/arm64/encodingindex.html#ldst_pos
```

It's incomplete as it doesn't yet handle all the encodings, but I work on it as needed.

On 05/09/2024 4:17 PM, Walter Bright wrote:
> I've been using godbolt.org to figure out which #AArch64 instructions are generated for which operations, as I find the instruction descriptions are frequently baffling.
> 
> But I've been reduced to taking the godbolt 8 bit hex instructions and compare them against the 2000 #AArch64 instructions to get a match (yes, the mnemonic helps a lot, but as many mnemonics have multiple encodings, it's back to tedium). It's laborious because the instruction encodings do not line up on byte boundaries, so I have to convert it to binary and then mark out the bit fields by hand (dammit D needs bit fields!)
> 
> I finally realized disasmarm.d can help. I fixed it so one just types in the 8 hex bytes on the command for the instruction, and it will disassemble it and provide the correct URL to the manual page for that instruction.
> 
> disasmarm.d can be compiled with:
> 
> ```
> dmd disasmarm.d -version=StandAlone
> ```
> 
> to make a standalone program and it will do a little disassembling:
> 
> ```
> ./disasmarm fd401bff
> FD 40 1B FF  ldr d31,[sp,#0x30] // https://www.scs.stanford.edu/~zyedidia/arm64/encodingindex.html#ldst_pos
> ```
> 
> It's incomplete as it doesn't yet handle all the encodings, but I work on it as needed.

At this rate we'll have our own objdump before a years end! (Year unspecified)

On 9/4/2024 10:31 PM, Richard (Rikki) Andrew Cattermole wrote:
> At this rate we'll have our own objdump before a years end! (Year unspecified)

We already have obj2asm, which does the same thing as objdump, and incorporates disasmarm. obj2asm already decodes ARM object files.

But objdump/obj2asm work off of .o files, which are not useful for looking at individual encodings, and don't provide a URL for the spec.