Summary

fixnum arithmetic is ignored

Metadata

Description

As reported by chickendan on IRC:

 ;; csc -O5 -strict-types -fixnum-arithmetic: 7.964s
 ;; csc -O5 -strict-types:                    8.105s
 ;; csc -O5 -strict-types (and fx functions): 0.246s
 ;;; c/nim -O3 baseline:                       0.211s
 
 (define (fib n)
   (if (or (= n 0) (= n 1))
       n
       (+ (fib (- n 1)) (fib (- n 2)))))
 
 (let loop ((n 0))
   (when (< n 35)
     (print "n=" n " => " (fib n))
     (loop (+ n 1))))

This program should use fixnum ops when declaring fixnum arithmetic. Also, when wrapping `fib`'s body in an `assume`, it still compiles to `C_s_a_i_plus` calls rather than `C_a_i_fixnum_plus` or even just `C_s_a_u_i_integer_plus`.

I think we should take a look before releasing 5.1, the fact `fixnum-arithmetic` is ignored may not be a big issue, but it is rather worrying that the specializations aren't used.

Changes and comments

[2019-04-10 10:52:59 UTC] sjamaan changed description

[2019-04-10 11:22:51 UTC] megane wrote:

The scrutinizer cannot handle recursion. The type of `fib` is `*` inside `fib`. This leads to the `+` being called with `*` arguments, so no specialization can happen.

You can wrap the body of `fib` in `assume` with `fib` declared as `(fixnum -> fixnum)`. I get `C_a_i_fixnum_plus` specializations with master this way.

Maybe `fixnum-arithmetic` is still broken, though.

[2019-05-29 16:41:33 UTC] sjamaan changed status from new to closed

[2019-05-29 16:41:33 UTC] sjamaan set resolution to fixed

[2019-05-29 16:41:33 UTC] sjamaan wrote:

The worst of this has been fixed by removing the scrutiny rewrites for `(* *)` in bc72c05f.

I've created new tickets to fix the remaining issues in 5.2 and beyond: See #1619 and #1620.