Poulpy Emitter

[martonmoro]

Step 3 (Implement Code Generation) from #3096.

Adds lib/Target/Poulpy/{PoulpyEmitter.h,.cpp,BUILD,PoulpyTemplates.h}
and registers the --emit-poulpy translation in heir-translate.

• ModuleOp printer: Rust prelude, backend detection from
  !poulpy.module argument types, type BE = ...; and derived type
  aliases (Ct/Tsk/Akm)
• func::FuncOp / func::ReturnOp printers: typed, mutability-aware
  argument list, Result return, zero/one-operand return handling
• convertType: !poulpy.module, !poulpy.scratch, !poulpy.tensor_key,
  !poulpy.automorphism_key_map, and rank-0
  memref<!poulpy.ciphertext> (&Ct/&mut Ct/Ct depending on position
  and mutation)
• Argument mutability analysis: decides &Ct vs &mut Ct from which
  values are written by a compute op in the function body
• Lazy memref.alloc materialization: a fresh ciphertext buffer's
  Rust allocation is synthesized at the first op that writes into
  it, deriving its layout at runtime from a sibling operand
• Rejects an _assign op whose dst is still unmaterialized, since
  that would silently read uninitialized memory
• Op printers: add, add_assign, sub, sub_assign, mul, mul_assign,
  rotate, rotate_assign

Adds tests/Emitter/Poulpy/{BUILD,emit_poulpy.mlir,
emit_poulpy_invalid_assign.mlir}. Output has also been verified with
cargo check against the real poulpy 0.7.0 crates, not just
pattern-matched.

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[j2kun]

Looks pretty good! I think it would be worth sharing a sample of the generated code with @Pro7ech to get a validation check on the API usage and the prelude.

[j2kun]

It might be worth adding one or two templated emitBinaryOp/emitBinaryAssignOp helper functions to reduce some of the duplication among these printers.

[martonmoro]

Looks pretty good! I think it would be worth sharing a sample of the generated code with @Pro7ech to get a validation check on the API usage and the prelude.

will do!