Re: Guile CSE elimination of record accessor?

[Simon Tournier]

Hi Andy,

Thanks for the explanations.

On mar., 30 avril 2024 at 16:43, Andy Wingo <wingo@igalia.com> wrote:

>> The first question is: is it still correct?  Because this module had
>> been implemented before many Guile compiler improvements.
>
> No, the comment is incorrect.  The type check on whatever accessor is
> called first (unspecified in scheme; probably we should just bite the
> bullet and do predictable left-to-right semantics, as racket does) will
> dominate the rest and eliminate those checks.  The assert-type is
> unnecessary.

Good to know.

> To see this, do ,optimize-cps at the repl, and count the number of
> e.g. struct? checks with and without the assert-vlist.  There is only
> one, either way.

Hum, I am not sure to understand how to use ,optimize-cps at the repl.
Naively, I get:

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> ,use(ice-9 vlist)
scheme@(guile-user)> ,optimize-cps (vlist-cons 'foo vlist-null)
L0:                                           ;              at <unknown>:102:14
  v0 := self
  L1(...)
L1:
  receive()
  v1 := current-module()                      ; mod While executing 
meta-command:
In procedure +: Wrong type argument in position 1: #f
--8<---------------cut here---------------end--------------->8---

Since ’,help compile’ reads,

    ,optimize-cps EXP         [,optx] - Run the CPS optimizer on a piece of 
code and print the result.

I assume that I do not feed with the correct expression EXP.  What would
be the invocation?


>                   (A type check is a heap-object? check, then struct?,
> then get the vtable, then check against the global variable <vlist>.
> All of these duplicates get eliminated.)

Ah yeah, it makes sense. :-)

Cheers,
simon