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

[Emanuel Peter]

On Thu, 20 Mar 2025 12:53:05 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> 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`

Or even: `after: v << 24`

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PR Review Comment: https://git.openjdk.org/jdk/pull/23728#discussion_r2005576711