embedded builtin's question

[Justin Ferguson]

Hello,

Is there an easy way to see the assembly routines generated by the
build process that ends up in embedded.cc? I'm trying to understand a
given function (LoadSuperIC), but the assembly in a debugger looks so
incredibly different than the function defined in accessor-assembly.cc
that I'm not positive I'm even looking at the same function. This is
compounded with what appears to be non-standard ABI calling
conventions or at least there are accesses to registers that are never
written to before reading from and which are not part of the
parameters (e.g. r13).

So it would be beneficial to my understanding to see the actual
assembly routine, but I'm not entirely positive where to start. Any
guidance would be appreciated.

Best Regards,

Justin N. Ferguson

[Jakob Gruber]

Hi Justin,

to see builtins disassembly, either:

- run mksnapshot as `out/release/mksnapshot --print-builtin-code --code-comments` (and build with `v8_enable_disassembler = true v8_enable_object_print = true` gn args), or:

- look at the `out/release/gen/embedded.S` file, this is what we finally compile into v8.

r13 is the kRootRegister, which points (roughly) at the current Isolate and is initialized by JSEntry. We use it to efficiently access isolate-specific data.

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[Justin Ferguson]

Hi Jakob,

> to see builtins disassembly, either:
>
> - run mksnapshot as `out/release/mksnapshot --print-builtin-code --code-comments` (and build with `v8_enable_disassembler = true v8_enable_object_print = true` gn args),

This was exactly what I was looking for, thank you.

> [...] or:

> - look at the `out/release/gen/embedded.S` file, this is what we finally compile into v8.

The .S file is basically the same as embedded.cc its just not wrapped
in __asm__()'s and contains like .section .rodata directives.

> r13 is the kRootRegister, which points (roughly) at the current Isolate and is initialized by JSEntry. We use it to efficiently access isolate-
> specific data.

This was very helpful as well, thank you.