Re: [patch] Fix address shape in cse.c:find_best_addr

[Kazu Hirata <kazu at cs dot umass dot edu>]

Hi Roger,

> > 	* cse.c (validize_addr): New function.
> > 	(find_best_addr): Use it.

Speaking of conversions between ASHIFT and MULT, do we have a
canonical way to represent ASHIFT/MULT in an address expression in
RTL?  We seem to have a quite bit of "back and forth" between ASHIFT
and MULT.  Unless we have a good reason, we should stick with one of
them.

Here are some places that do conversions.

1) validize_addr changes ASHIFT to MULT.

2) canon_for_address also changes ASHIFT to MULT.

3) According to Steven Bosscher, given this insn

(insn 215 214 216 15 (parallel [ 
            (set (reg:DI 176) 
                (ashift:DI (reg:DI 175) 
                    (const_int 3 [0x3]))) 
            (clobber (reg:CC 17 flags)) 
        ]) -1 (nil) 
    (expr_list:REG_EQUAL (mult:DI (reg:DI 174) 
            (const_int 8 [0x8])) 
        (nil))) 

and this rtx

(mult:DI (reg:DI 174) 
    (const_int 8 [0x8])) 

fold_rtx returns

(ashift:DI (reg:DI 174) 
    (const_int 3 [0x3])) 
 
Note that this particular REG_EQUAL doesn't tell us anything
interesting.  OK, this 3) isn't strictly a conversion, but still we
are playing with ASHIFT and MULT.

By the way, now that I am looking at canon_for_address, I wonder
whether validize_addr can be merged into canon_for_address (or vice
versa).  Zdenek, have you looked at canon_for_address before you wrote
validize_addr?

Kazu Hirata