[patch] Disable old loop optimizer

[Giovanni Bajo]

Paul Schlie <schlie@comcast.net> wrote:

>>> 2) loop reversal (i.e. replacing "for (i = 0; i < n; i++) a[i]=i;"
>>>    with "for (i = n - 1; i >= 0; i--) a[i]=i;", thus causing us to
>>>    compare with zero instead of arbitrary bound, and possibly
>>>    shorten the life range of n).  Should be trivial within
>>>    linear-transform framework, the major problem is to decide when
>>>    it is really useful. the major problem is to decide when it is
>>> really useful.
>
> It should be considered to be universally useful: as comparing a value
> against a constant 0 is never more expensive than comparing it
> against an arbitrary constant, [...]

You are totally missing the point: reversing a loop is not the same thing of
reversing just its counter. You should go reading loop-doloop.c.

Giovanni Bajo