[Ecls-list] INCF/1+ and LOOP differences at same OPTIMIZE/SAFETY levels

[Matthew Mondor]

Hello,

I noticed that on -current ECL, using the same OPTIMIZE
SPEED/SAFETY/DEBUG levels
(optimize (speed 3) (safety 1) (debug 1))

When using the LOOP macro with variables known to be FIXNUM, the
increment can be optimized inline using C + directly without further
checks.  However, if using INCF or SETF/1+, an explicit call to
ecl_one_plus() is generated, even if the variable is known as a FIXNUM.

Initially, I thought that it was because the compiler could infer the
upper value the variable would reach (in which case it's a great
optimization), but I noticed that even on variables without an upper
bound (i.e. for i of-type fixnum from 0), inline + is also used.

So this made me wonder: is ecl_one_plus() used for safety at that
safety level (1) because of potential wrapping in the INCF/1+ case?  If
so, shouldn't LOOP also use ecl_one_plus() at that same safety level?
At SAFETY 0 DEBUG 0 SPEED 3, both INCF and LOOP get inlined, yet the
SETF/1+ case still uses ecl_plus_one().

(Attached is example code and indented C results)

Thanks again,
-- 
Matt
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