monomorphize is a toplevel optimization attribute for declare and define.

Syntax

(monomorphize)
(declare ⟨name⟩ ⟨monomorphic-type⟩)
(define (⟨name⟩ ⟨arg⟩ ...)
  ⟨body⟩)

Semantics

  • (monomorphize) must appear immediately before a declare or define form.
  • It marks the binding for Coalton’s monomorphization pass during optimization.
  • This is mainly useful when the implementation is written in terms of generic class-constrained operations, but the binding itself has a concrete declared type.
  • In practice this often means numerically generic bodies that use operators like +, *, or <, while the exported function is declared at a single concrete type such as Integer or Double-Float.
  • monomorphize is an optimization hint and should not change observable behavior.

Example

(coalton-toplevel
  (monomorphize)
  (declare axpy (F32 * F32 * F32 -> F32))
  (define (axpy a x y)
    (+ (* a x) y)))

Here the body is ordinary generic numeric code, which would normally compile into generic calls, even with the monomorphic declaration. monomorphize rewrites all of the calls to monomorphic ones, which we can observe in this ARM64 disassembly:

COALTON-USER> (disassemble #'axpy)
; disassembly for AXPY
; Size: 48 bytes. Origin: #x7021136678                        ; AXPY
; 78:       AA0A40F9         LDR R0, [THREAD, #16]            ; binding-stack-pointer
; 7C:       AA0B00F9         STR R0, [CFP, #16]

; 80:       6008221E         FMUL S0, S3, S2
; 84:       0028211E         FADD S0, S0, S1

; 88:       0100261E         FMOV WNL1, S0
; 8C:       217C60D3         LSL NL1, NL1, #32
; 90:       2A640091         ADD R0, NL1, #25
; 94:       FB031DAA         MOV CSP, CFP
; 98:       5F0300F1         CMP NULL, #0
; 9C:       BD7B40A9         LDP CFP, LR, [CFP]
; A0:       C0035FD6         RET
; A4:       E00120D4         BRK #15                          ; Invalid argument count trap