On Mon, 28 Oct 2024 07:10:59 GMT, Jatin Bhateja <jbhat...@openjdk.org> wrote:

> The application of lowering is very broad as it can help us perform arbitrary 
> transformation as well as take advantages of GVN 

@merykitty thanks for the examples. The idea of gradual IR lowering is not new 
in C2. There are precedents in the code base, so I'd like to better understand 
how the new pass improves the overall situation. Introducing a way to perform 
arbitrary platform-specific transformations on Ideal does sound very powerful, 
but it also turns Ideal IR into platform-specific dialects which don't have to 
work with existing transformations (IGVN, in particular).

Do the use cases mentioned so far justify a platform-specific lowering pass on 
Ideal IR which is intended to produce platform-specific Ideal IR shapes? I 
don't know yet.

Also, there are alternative places where platform-specific transformations can 
take place (macro expansion, final graph reshaping, custom matching logic). 
Worth considering them as well.

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PR Comment: https://git.openjdk.org/jdk/pull/21599#issuecomment-2442814693

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