RFR: 8326135: Enhance adlc to report unused operands [v2]

[Vladimir Kozlov]

On Wed, 21 Feb 2024 02:49:30 GMT, kuaiwei <duke at openjdk.org> wrote:

>> src/hotspot/share/adlc/archDesc.cpp line 739:
>> 
>>> 737:   callback.do_form_by_name("stackSlotL");
>>> 738: 
>>> 739:   // special generic vector operands used in Matcher::pd_specialize_generic_vector_operand
>> 
>> What is special about `stackSlot*` and `vec*` operands to process them explicitly here?
>
> stackSlot* are used in output_h.cpp and formssel.cpp . I assume they are all useful.
> 
> Generic vector operands are not used in instruction forms. But they are used in c++ code snippet Matcher::pd_specialize_generic_vector_operand(). The special vector operands only exists in x86_64 and aarch64 platform.

I actually asked why `callback.do_form(instr)` calls in loop are not marking them as used? Why you need to call `do_form_by_name()` for them?

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PR Review Comment: https://git.openjdk.org/jdk/pull/17910#discussion_r1496835669