Equality via pattern-matching compiles to slow code

[jvanburen]

example:

  type t =
    | Naked_immediate
    | Naked_float32
    | Naked_float
    | Naked_int8
    | Naked_int16
    | Naked_int32
    | Naked_int64
    | Naked_nativeint
    | Naked_vec128

  let equal t1 t2 =
    match t1, t2 with
    | Naked_immediate, Naked_immediate -> true
    | Naked_float32, Naked_float32 -> true
    | Naked_float, Naked_float -> true
    | Naked_int8, Naked_int8 -> true
    | Naked_int16, Naked_int16 -> true
    | Naked_int32, Naked_int32 -> true
    | Naked_int64, Naked_int64 -> true
    | Naked_nativeint, Naked_nativeint -> true
    | Naked_vec128, Naked_vec128 -> true
    | ( ( Naked_immediate | Naked_float32 | Naked_float | Naked_int8
        | Naked_int16 | Naked_int32 | Naked_int64 | Naked_nativeint
        | Naked_vec128 ),
        _ ) ->
      false

leads to

camlExample.equal_1:
        .quad   caml_curry2
        .quad   0x280000000000007
        .quad   camlExample.equal_0_1_code
        .quad   0xffc
        .ascii  "unreachable switch case"
        .byte   0
camlExample.equal_0_1_code:
        sar     rax
        lea     rdx, [rip + .L185]
        movsxd  rax, dword ptr [rdx + 4*rax]
        add     rdx, rax
        jmp     rdx
.L117:
        cmp     rbx, 1
        je      .L121
        mov     eax, 1
        ret
.L121:
        mov     eax, 3
        ret
.L124:
        cmp     rbx, 3
        je      .L128
        mov     eax, 1
        ret
.L128:
        mov     eax, 3
        ret
.L131:
        cmp     rbx, 5
        je      .L135
        mov     eax, 1
        ret
.L135:
        mov     eax, 3
        ret
.L138:
        cmp     rbx, 7
        je      .L142
        mov     eax, 1
        ret
.L142:
        mov     eax, 3
        ret
.L145:
        cmp     rbx, 9
        je      .L149
        mov     eax, 1
        ret
.L149:
        mov     eax, 3
        ret
.L152:
        cmp     rbx, 11
        je      .L156
        mov     eax, 1
        ret
.L156:
        mov     eax, 3
        ret
.L159:
        cmp     rbx, 13
        je      .L163
        mov     eax, 1
        ret
.L163:
        mov     eax, 3
        ret
.L166:
        cmp     rbx, 15
        je      .L170
        mov     eax, 1
        ret
.L170:
        mov     eax, 3
        ret
.L173:
        cmp     rbx, 17
        jl      .L177
        mov     eax, 3
        ret
.L177:
        mov     eax, 1
        ret