[Bug target/62631] gcc.dg/tree-ssa/ivopts-lt-2.c FAILs

[amker at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62631

--- Comment #32 from amker at gcc dot gnu.org ---
(In reply to dave.anglin from comment #30)
> On 2015-02-08, at 9:09 AM, amker at gcc dot gnu.org wrote:
> 
> > Ah, candidate 5 is considered cheaper according to the cost table.
> 
> Is this a problem with insn costs, or a problem in the estimation of the
> total cost
> for each candidate?
The total cost I think.  Cost in IVOPT is tricky and inaccurate since 1) it
needs to estimate cost of RTL on gimple IR; 2) The rtx expression cost is
computed together with address expression cost, which doesn't happen in other
part of GCC.  
I can try to make the case less vulnerable for now.  Should we consider this as
a missed optimization since GCC never did the optimization for the case before
(and still not for mentioned targets)?

Thanks,
bin
> 
> Dave
> --
> John David Anglin	dave.anglin@bell.net