[Chicken-janitors] #1611: Restructure checks for inlinable intrinsics

[Chicken Trac]

#1611: Restructure checks for inlinable intrinsics
-------------------------------------+-------------------------------------
 Reporter:  sjamaan                  |                 Owner:  sjamaan
     Type:  enhancement              |                Status:  new
 Priority:  major                    |             Milestone:  5.2
Component:  compiler                 |               Version:
 Keywords:  inlining, intrinsics,    |  Estimated difficulty:  medium
  performance, lfa2, code            |
  duplication                        |
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 Currently, we have a lot of intrinsics which are inlinable. Sometimes the
 safe inlineable versions are missing, sometimes the unsafe ones are
 missing. It also means there is a *lot* of handwritten C code with
 duplications.

 There would be less duplication if the compiler knew that the safe version
 is actually (roughly) an argument check followed by an unsafe call.

 For example:

 - `C_a_i_log` is just `C_check_real` followed by `C_flonum(a, log(f))`
 - `C_a_i_flonum_log` is `C_flonum(a, C_log(C_flonum_magnitude(x)))` (it
 should actually have a `_u_` in its name)

 Same is true for all the arithmetic operators in `(chicken flonum)`. At
 least for flonums, I think it's quite doable to have just the unsafe
 version and have some sort of "rewrite" in the compiler which will do the
 check followed by a call to the unsafe one.

 This can be done for a lot of other intrinsics too; think all the `char=`,
 `char<`, `char-upcase`, etc.

 This would give us a lot of faster implementations of safe operations "for
 free" by rewriting them to the unsafe ones, and if I'm not mistaken, we'd
 end up with a lot of calls to the "check" procedures, which ties in nicely
 with lfa2, which means all but the first can be eliminated.


 I'm thinking something like this:

 ```
 (define-intrinsic (chicken.flonum#fp+ x y)
   (check-flonum x)
   (check-flonum y)
   (##core#inline_allocate ("C_a_i_flonum_plus" 4) x y) ;; to be renamed to
 C_a_u_i_flonum_plus?
 )

 (define-intrinsic (scheme#integer->char n)
   (check-fixnum n 'integer->char)
   (##core#inline "C_make_character" (##core#inline "C_unfix" n))
 )
 ```

 This could even replace the definitions in `library.scm`; then when we are
 compiling, we could process this code to generate an intrinsics database
 file, which the compiler can use like types.db.  The above `define-
 intrinsic` would collapse to a simple `define` while generating
 `library.so`.

 When the compiler is compiling with an intrinsics database, it can replace
 all calls with the inlinable versions.

 Perhaps this is simply a more controlled way of doing `-emit-inline-file`?

 This isn't difficult but a lot of work and some care needs to be taken
 with regards to backwards C API/binary compatibility.

--
Ticket URL: <https://bugs.call-cc.org/ticket/1611>
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