| Message ID | 20121022210936.GJ1752@tucnak.redhat.com |
|---|---|
| State | New |
| Headers | show |
On Mon, Oct 22, 2012 at 11:09 PM, Jakub Jelinek <jakub@redhat.com> wrote: > Wouldn't it be way cheaper to just export dfs_find_deadend from cfganal.c > and call it in calc_dfs_tree on each unconnected bb? > I.e. (untested with the exception of the testcase): Better yet, I have a patch in testing now to use cfganal's machinery to compute the DFS forest. Hold on a bit, I'll post it ASAP (probably Wednesday) if that's early enough for you. (Oh, and feel free to assign the PR to me ;-) Ciao! Steven
On Mon, Oct 22, 2012 at 11:09 PM, Jakub Jelinek wrote: > On Mon, Oct 22, 2012 at 10:51:43PM +0200, Steven Bosscher wrote: > Wouldn't it be way cheaper to just export dfs_find_deadend from cfganal.c > and call it in calc_dfs_tree on each unconnected bb? > I.e. (untested with the exception of the testcase): > > 2012-10-22 Jakub Jelinek <jakub@redhat.com> > > PR tree-optimization/55018 > * cfganal.c (dfs_find_deadend): No longer static. > * basic-block.h (dfs_find_deadend): New prototype. > * dominance.c (calc_dfs_tree): If saw_unconnected, > traverse from dfs_find_deadend of unconnected b > instead of b directly. > > * gcc.dg/torture/pr55018.c: New test. I have no better solution than this for the moment. I thought there was a common DFS machinery in cfganal.c but there are actually many of them, but unfortunately all doing things slightly different. Something for the cleanup list for GCC 4.9... We should use dfs_find_deadend in flow_dfs_compute_reverse_execute also. This results in fewer fake edges created in connect_infinite_loops_to_exit, especially for loops with multiple dead ends. (BTW, connect_infinite_loops_to_exit also connects other reverse-unreachable points in the CFG to EXIT, so that calling add_noreturn_fake_exit_edges and connect_infinite_loops_to_exit is doing a bit of duplicate work -- another thing for the cleanup list...) Attached patch was bootstrapped&tested on {powerpc64,x86_64}-unknown-linux-gnu. OK? Ciao! Steven
On Sun, Oct 28, 2012 at 7:33 PM, Steven Bosscher <stevenb.gcc@gmail.com> wrote: > On Mon, Oct 22, 2012 at 11:09 PM, Jakub Jelinek wrote: >> On Mon, Oct 22, 2012 at 10:51:43PM +0200, Steven Bosscher wrote: >> Wouldn't it be way cheaper to just export dfs_find_deadend from cfganal.c >> and call it in calc_dfs_tree on each unconnected bb? >> I.e. (untested with the exception of the testcase): >> >> 2012-10-22 Jakub Jelinek <jakub@redhat.com> >> >> PR tree-optimization/55018 >> * cfganal.c (dfs_find_deadend): No longer static. >> * basic-block.h (dfs_find_deadend): New prototype. >> * dominance.c (calc_dfs_tree): If saw_unconnected, >> traverse from dfs_find_deadend of unconnected b >> instead of b directly. >> >> * gcc.dg/torture/pr55018.c: New test. > > I have no better solution than this for the moment. I thought there > was a common DFS machinery in cfganal.c but there are actually many of > them, but unfortunately all doing things slightly different. Something > for the cleanup list for GCC 4.9... > > We should use dfs_find_deadend in flow_dfs_compute_reverse_execute > also. This results in fewer fake edges created in > connect_infinite_loops_to_exit, especially for loops with multiple > dead ends. > > (BTW, connect_infinite_loops_to_exit also connects other > reverse-unreachable points in the CFG to EXIT, so that calling > add_noreturn_fake_exit_edges and connect_infinite_loops_to_exit is > doing a bit of duplicate work -- another thing for the cleanup > list...) > > Attached patch was bootstrapped&tested on > {powerpc64,x86_64}-unknown-linux-gnu. OK? Ok. Thanks, Richard. > Ciao! > Steven
On Thu, Nov 01, 2012 at 09:26:25PM +0100, Hans-Peter Nilsson wrote: > > Attached patch was bootstrapped&tested on > > gcc/ > PR tree-optimization/55018 > * basic-block.h (dfs_find_deadend): New prototype. > * cfganal.c (dfs_find_deadend): No longer static. Use bitmap > instead of sbitmap for visited. > (flow_dfs_compute_reverse_execute): Use dfs_find_deadend here, too. > * dominance.c (calc_dfs_tree): If saw_unconnected, > traverse from dfs_find_deadend of unconnected b > instead of b directly. > > It seems this caused PR55168, ICE. As Honza said, it was likely latent, and furthermore seems to be related to the flow_dfs_compute_reverse_execute change from Steven (mentioning it primarily what should we consider backporting if anything to release branches). Jakub
> On Thu, Nov 01, 2012 at 09:26:25PM +0100, Hans-Peter Nilsson wrote: > > > Attached patch was bootstrapped&tested on > > > > gcc/ > > PR tree-optimization/55018 > > * basic-block.h (dfs_find_deadend): New prototype. > > * cfganal.c (dfs_find_deadend): No longer static. Use bitmap > > instead of sbitmap for visited. > > (flow_dfs_compute_reverse_execute): Use dfs_find_deadend here, too. > > * dominance.c (calc_dfs_tree): If saw_unconnected, > > traverse from dfs_find_deadend of unconnected b > > instead of b directly. > > > > It seems this caused PR55168, ICE. > > As Honza said, it was likely latent, and furthermore seems to be related to > the flow_dfs_compute_reverse_execute change from Steven (mentioning it > primarily what should we consider backporting if anything to release > branches). Indeed, this patch should not affect loop predictions. Perhaps it prevents CD-DCE from removing a loop that it previously removed and thus the loop survives till predict.c and triggers the previously latent bugs? The patch I attached to the PR is actually incorrect - estimated_stmt_executions_int already adds the +1 and thus should never return 0. I am looking into proper fix. There is obvious overflow on the other computation patch, so my best guess is that fixing it will cure the issue. Honza > > Jakub
--- gcc/cfganal.c.jj 2012-08-14 08:45:00.000000000 +0200 +++ gcc/cfganal.c 2012-10-22 23:04:29.620117666 +0200 @@ -593,7 +593,7 @@ post_order_compute (int *post_order, boo that all blocks in the region are reachable by starting an inverted traversal from the returned block. */ -static basic_block +basic_block dfs_find_deadend (basic_block bb) { sbitmap visited = sbitmap_alloc (last_basic_block); --- gcc/basic-block.h.jj 2012-10-17 17:18:21.000000000 +0200 +++ gcc/basic-block.h 2012-10-17 17:18:21.000000000 +0200 @@ -787,6 +787,7 @@ extern void remove_fake_exit_edges (void extern void add_noreturn_fake_exit_edges (void); extern void connect_infinite_loops_to_exit (void); extern int post_order_compute (int *, bool, bool); +extern basic_block dfs_find_deadend (basic_block); extern int inverted_post_order_compute (int *); extern int pre_and_rev_post_order_compute (int *, int *, bool); extern int dfs_enumerate_from (basic_block, int, --- gcc/dominance.c.jj 2012-08-15 10:55:26.000000000 +0200 +++ gcc/dominance.c 2012-10-22 23:07:00.941220792 +0200 @@ -377,14 +377,18 @@ calc_dfs_tree (struct dom_info *di, bool { FOR_EACH_BB_REVERSE (b) { + basic_block b2; if (di->dfs_order[b->index]) continue; - bitmap_set_bit (di->fake_exit_edge, b->index); - di->dfs_order[b->index] = di->dfsnum; - di->dfs_to_bb[di->dfsnum] = b; + b2 = dfs_find_deadend (b); + gcc_checking_assert (di->dfs_order[b2->index] == 0); + bitmap_set_bit (di->fake_exit_edge, b2->index); + di->dfs_order[b2->index] = di->dfsnum; + di->dfs_to_bb[di->dfsnum] = b2; di->dfs_parent[di->dfsnum] = di->dfs_order[last_basic_block]; di->dfsnum++; - calc_dfs_tree_nonrec (di, b, reverse); + calc_dfs_tree_nonrec (di, b2, reverse); + gcc_checking_assert (di->dfs_order[b->index]); } } } --- gcc/testsuite/gcc.dg/torture/pr55018.c.jj 2012-10-22 16:53:56.623083723 +0200 +++ gcc/testsuite/gcc.dg/torture/pr55018.c 2012-10-22 16:54:21.278934668 +0200 @@ -0,0 +1,22 @@ +/* PR tree-optimization/55018 */ +/* { dg-do compile } */ +/* { dg-options "-fdump-tree-optimized" } */ + +void +foo (int x) +{ + unsigned int a = 0; + int b = 3; + if (x) + b = 0; +lab: + if (x) + goto lab; + a++; + if (b != 2) + __builtin_printf ("%u", a); + goto lab; +} + +/* { dg-final { scan-tree-dump "printf" "optimized" } } */ +/* { dg-final { cleanup-tree-dump "optimized" } } */