Commits on Apr 6, 2023

1. Cranelift: remove non-egraphs optimization pipeline and use_egraphs… …

   … option.
   
   This PR removes the LICM, GVN, and preopt passes, and associated support
   pieces, from `cranelift-codegen`. Not to worry, we still have
   optimizations: the egraph framework subsumes all of these, and has been
   on by default since bytecodealliance#5181.
   
   A few decision points:
   
   - Filetests for the legacy LICM, GVN and simple_preopt were removed too.
     As we built optimizations in the egraph framework we wrote new tests
     for the equivalent functionality, and many of the old tests were
     testing specific behaviors in the old implementations that may not be
     relevant anymore. However if folks prefer I could take a different
     approach here and try to port over all of the tests.
   
   - The corresponding filetest modes (commands) were deleted too. The
     `test alias_analysis` mode remains, but no longer invokes a separate
     GVN first (since there is no separate GVN that will not also do alias
     analysis) so the tests were tweaked slightly to work with that. The
     egrpah testsuite also covers alias analysis.
   
   - The `divconst_magic_numbers` module is removed since it's unused
     without `simple_preopt`, though this is the one remaining optimization
     we still need to build in the egraphs framework, pending bytecodealliance#5908. The
     magic numbers will live forever in git history so removing this in the
     meantime is not a major issue IMHO.
   
   - The `use_egraphs` setting itself was removed at both the Cranelift and
     Wasmtime levels. It has been marked deprecated for a few releases now
     (Wasmtime 6.0, 7.0, upcoming 8.0, and corresponding Cranelift
     versions) so I think this is probably OK. As an alternative if anyone
     feels strongly, we could leave the setting and make it a no-op.

   

   cfallin committed Apr 6, 2023
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2. Update test outputs for remaining test differences.

   

   cfallin committed Apr 6, 2023
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