RFR: 8347459: C2: missing transformation for chain of shifts/multiplications by constants [v15]

[Emanuel Peter]

On Thu, 20 Mar 2025 12:52:35 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Marc Chevalier has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   more checks
>
> src/hotspot/share/opto/memnode.cpp line 3563:
> 
>> 3561: // ###### Case 1.1: conIL == conIR == num_rejected_bits
>> 3562: // If we do the shift left then right by 24 bits, we get:
>> 3563: // after << 24
> 
> Suggestion:
> 
> // after "<< 24"
> 
> This could help visually, I had to stare at it for 3 sec until I knew it was not a shifting of `after`, i.e. `after << 24`

Alternatively something like `after: << 24`

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PR Review Comment: https://git.openjdk.org/jdk/pull/23728#discussion_r2005574740