[OCaml] Completely remove legacy SCCP pass

[alan]

Summary

This completely removes the SCCP pass in the OCaml bindings, fixing the
build and tests.

[alan]

The commit e2cd0851faaba39cc04c3059df25d22a02b1e682 did not completely remove the SCCP pass from the OCaml bindings, breaking them.

Once this is approved, I'll need someone else to land this because I don't have access to the main branch.

[nikic]

Let's please remove all legacy passes from the OCaml bindings in one go, so they don't get broken all the time as the pass implementations get dropped one by one.

[alan]

Ok. However, I think this patch should be trivial to land on main, and getting rid of all the legacy passes in one go can be another patch. I would prefer if the OCaml bindings were not broken on main, because I have another patch (https://reviews.llvm.org/D136400) that needs to be rebased, and I can't rebase on a broken build.

As someone who doesn't follow the C API, where can I find out information about which passes are to be removed? Recently there's been some churn and I've frequently had to rebase my other patch. I would like to know how I could be more involved in C API changes and how they interact with the OCaml bindings.

[aeubanks]

pretty much anything with PassManager in it in the current ocaml bindings will be removed

[alan]

Should I change this patch to remove all the PassManager-related functions from the OCaml bindings?

[alan]

I now have https://reviews.llvm.org/D144751 as an alternative to this patch.

[alan]

Subsumed by https://reviews.llvm.org/D144751.

llvm/bindings/ocaml/transforms/scalar_opts/llvm_scalar_opts.ml

external add_lower_switch
   : [< Llvm.PassManager.any ] Llvm.PassManager.t -> unit
   = "llvm_add_lower_switch"
 external add_memory_to_register_promotion
   : [< Llvm.PassManager.any ] Llvm.PassManager.t -> unit
   = "llvm_add_promote_memory_to_register"
 external add_reassociation
   : [< Llvm.PassManager.any ] Llvm.PassManager.t -> unit
   = "llvm_add_reassociation"
-external add_sccp
-  : [< Llvm.PassManager.any ] Llvm.PassManager.t -> unit
-  = "llvm_add_sccp"
 external add_scalar_repl_aggregation
   : [< Llvm.PassManager.any ] Llvm.PassManager.t -> unit
   = "llvm_add_scalar_repl_aggregates"
 external add_scalar_repl_aggregation_ssa
   : [< Llvm.PassManager.any ] Llvm.PassManager.t -> unit
   = "llvm_add_scalar_repl_aggregates_ssa"
 external add_scalar_repl_aggregation_with_threshold
   : int -> [< Llvm.PassManager.any ] Llvm.PassManager.t -> unit

llvm/test/Bindings/OCaml/scalar_opts.ml

ignore (PassManager.create_function m
            ++ add_licm
            ++ add_loop_rotation
            ++ add_loop_unroll
            ++ add_memcpy_opt
            ++ add_partially_inline_lib_calls
            ++ add_lower_switch
            ++ add_memory_to_register_promotion
            ++ add_reassociation
-           ++ add_sccp
            ++ add_scalar_repl_aggregation
            ++ add_scalar_repl_aggregation_ssa
            ++ add_scalar_repl_aggregation_with_threshold 4
            ++ add_lib_call_simplification
            ++ add_tail_call_elimination
            ++ add_memory_to_register_demotion
            ++ add_verifier
            ++ add_correlated_value_propagation