| Message ID | alpine.LSU.2.11.1608221023530.26629@t29.fhfr.qr |
|---|---|
| State | New |
| Headers | show |
This causes a performance regression in the xalancbmk SPECint2006 benchmark on s390x. At first sight, the produced asm output doesn't look too different but I'll have a closer look. Is the fwprop order supposed to have major performance implications? Regards Robin > This changes it from PRE on the inverted graph to RPO order which works > better for loops and blocks with no path to exit. > > Bootstrapped and tested on x86_64-unknown-linux-gnu, applied. > > Richard. > > 2016-08-22 Richard Biener <rguenther@suse.de> > > * tree-ssa-forwprop.c (pass_forwprop::execute): Use RPO order. > > Index: gcc/tree-ssa-forwprop.c > =================================================================== > --- gcc/tree-ssa-forwprop.c (revision 239607) > +++ gcc/tree-ssa-forwprop.c (working copy) > @@ -2099,7 +2099,8 @@ pass_forwprop::execute (function *fun) > lattice.create (num_ssa_names); > lattice.quick_grow_cleared (num_ssa_names); > int *postorder = XNEWVEC (int, n_basic_blocks_for_fn (fun)); > - int postorder_num = inverted_post_order_compute (postorder); > + int postorder_num = pre_and_rev_post_order_compute_fn (cfun, NULL, > + postorder, false); > auto_vec<gimple *, 4> to_fixup; > to_purge = BITMAP_ALLOC (NULL); > for (int i = 0; i < postorder_num; ++i) >
On Fri, 2 Sep 2016, Robin Dapp wrote: > This causes a performance regression in the xalancbmk SPECint2006 > benchmark on s390x. At first sight, the produced asm output doesn't look > too different but I'll have a closer look. Is the fwprop order supposed > to have major performance implications? No, the change may allow a more copy propagation in loops but I didn't expect any major code generation changes from it. I've mainly done the change for consistency (for a forward SSA propagation pass RPO oder is the proper one). So if you can come up with a testcase I can investigate if the change is undesired. Thanks, Richard.
Index: gcc/tree-ssa-forwprop.c =================================================================== --- gcc/tree-ssa-forwprop.c (revision 239607) +++ gcc/tree-ssa-forwprop.c (working copy) @@ -2099,7 +2099,8 @@ pass_forwprop::execute (function *fun) lattice.create (num_ssa_names); lattice.quick_grow_cleared (num_ssa_names); int *postorder = XNEWVEC (int, n_basic_blocks_for_fn (fun)); - int postorder_num = inverted_post_order_compute (postorder); + int postorder_num = pre_and_rev_post_order_compute_fn (cfun, NULL, + postorder, false); auto_vec<gimple *, 4> to_fixup; to_purge = BITMAP_ALLOC (NULL); for (int i = 0; i < postorder_num; ++i)