Can compiler macros make use of type declarations?

[Chaitanya Gupta]

On 9 November 2017 at 16:42, Martin Simmons <martin at lispworks.com> wrote:
> Compiler macros are expanded too early to get inferred type info.  For
> example,
>
> (let ((y 10)) (loop (bar y) (setq y :not-a-fixnum)))

Right. That makes sense. So it seems declarations is the way to go if
you want to make type based optimizations.

Chaitanya

>
> --
> Martin Simmons
> LispWorks Ltd
> http://www.lispworks.com/
>
>
>>>>>> On Thu, 9 Nov 2017 14:47:53 +0530, Chaitanya Gupta said:
>>
>> I tried this on SBCL:
>>
>> (defun bar (x)
>>   x)
>>
>> (define-compiler-macro bar (&whole form x &environment env)
>>   (when (symbolp x)
>>     (print (multiple-value-list (clast:variable-information x env))))
>>   form)
>>
>> The form below, with the declaration, prints type information correctly:
>>
>> (compile nil
>>          (lambda ()
>>            (let ((y 10)) (declare (fixnum y)) (bar y))))
>> >> (:LEXICAL T ((TYPE . FIXNUM)))
>>
>> However, the one below with no declarations, doesn't give any info:
>>
>> (compile nil
>>          (lambda ()
>>            (let ((y 10)) (bar y))
>>            (let ((y '(1 2 3))) (bar y))
>>            (let ((y 'foo)) (bar y))))
>> >> (:LEXICAL T NIL)
>> >> (:LEXICAL T NIL)
>> >> (:LEXICAL T NIL)
>>
>> So I guess that, at least on SBCL, this is not possible.
>>
>> Chaitanya
>>
>>
>> On 9 November 2017 at 14:09, Antoniotti Marco
>> <antoniotti.marco at disco.unimib.it> wrote:
>> > CMUCL and SBCL have the Environment API somewhat available (*)
>> >
>> > You can see whether they store the inferred values in there.
>> >
>> > Marco
>> >
>> > (*) Again, you can have a look at CLAST to see how to access it; I know: it is a shameless plug.
>> >
>> >
>> >
>> >> On Nov 9, 2017, at 09:18 , Chaitanya Gupta <mail at chaitanyagupta.com> wrote:
>> >>
>> >> So thanks to the replies on this I now know that most of the popular
>> >> Lisps do support inspecting the environment to figure out declared
>> >> types.
>> >>
>> >> But what about inferred types (e.g. in CMUCL, SBCL)? Do these Lisps
>> >> provide a way to know the inferred type of a variable if no
>> >> declaration was made explicitly?
>> >>
>> >> Chaitanya
>> >>
>> >> On 7 November 2017 at 02:13, Chaitanya Gupta <mail at chaitanyagupta.com> wrote:
>> >>> Let's say I have created a function called `FOO`:
>> >>>
>> >>> (defun foo (x)
>> >>>  ...)
>> >>>
>> >>> To optimize this function, I write a compiler macro. Can I make use of
>> >>> type declarations that users of `FOO` might have made for the argument
>> >>> `X` that is passed in to it?
>> >>>
>> >>> That is, let's say `FOO` is used like this:
>> >>>
>> >>> (let ((a (something-that-returns-an-integer)))
>> >>>  (declare (integer a))
>> >>>  (foo a))
>> >>>
>> >>> The compiler macro for `FOO` cannot make any optimizations on the
>> >>> value of `A`, but can it take advantage of the fact that `A` is
>> >>> declared as in `INTEGER` here?
>> >>>
>> >>> Chaitanya
>> >>
>> >
>> > --
>> > Marco Antoniotti, Associate Professor           tel.    +39 - 02 64 48 79 01
>> > DISCo, Università Milano Bicocca U14 2043               http://bimib.disco.unimib.it
>> > Viale Sarca 336
>> > I-20126 Milan (MI) ITALY
>> >
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>> >
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>>
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>