------- Comment #11 from richard dot guenther at gmail dot com 2006-03-22
15:06 -------
Subject: Re: [4.1/4.2 Regression] missed jump threading after unroller
On 3/22/06, Jeffrey A Law <[EMAIL PROTECTED]> wrote:
> On Wed, 2006-03-22 at 12:14 +0100, Richard Guenther wrote:
> > On 3/21/06, Jeffrey A Law <[EMAIL PROTECTED]> wrote:
> > > It turns out this specialized PHI optimization pass is as effective
> > > as running copy-prop and CCP on PHI nodes after DOM. Better yet, it
> > > is a teeny tiny slowdown compared to just running the stripped down
> > > copyprop. ie, for an almost unmeasurable slowdown we can do both
> > > constant and copy propagation instead of just copy propagation.
> >
> > This patch caused a compile-time regression from 139s to 143s, resp.
> > 192s to 197s (leafify) accounted by increases of operand scan / SSA
> > incremental
> > and tree CCP times for compiling tramp3d. Also memory usage during
> > compiling
> > went up from 655494 kB to 660626kB (this may be due to the VRP patch,
> > though).
> >
> > Runtime of tramp3d did not improve but regress slightly (but that
> > might be in the
> > noise - we'll see).
> >
> > For this simple cleanup pass can you try updating SSA form manually please?
> I'm more than happy to look at it; however, be aware that if you're
> seeing increased time in CCP then either you're seeing some truly
> bizzarre secondary effect or your testing methodology is suspect.
> The patch did not affect CCP. In fact, the changes only affect
> passes which run *after* CCP in the optimization pipeline.
struct tree_opt_pass pass_phi_only_cprop =
{
"phicprop", /* name */
gate_dominator, /* gate */
eliminate_degenerate_phis, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
TV_TREE_CCP, /* tv_id */
PROP_cfg | PROP_ssa | PROP_alias, /* properties_required */
0, /* properties_provided */
PROP_smt_usage, /* properties_destroyed */
0, /* todo_flags_start */
TODO_cleanup_cfg | TODO_dump_func
| TODO_ggc_collect | TODO_verify_ssa
| TODO_verify_stmts | TODO_update_smt_usage
| TODO_update_ssa, /* todo_flags_finish */
0 /* letter */
};
see tv_id - so I guess increased CCP times are expected.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21829
