On Fri, Oct 2, 2015 at 9:30 PM, Jeff Law <l...@redhat.com> wrote: > On 10/02/2015 05:15 AM, Renlin Li wrote: >> >> Hi Jeff, >> >> Your patch causes an ICE regression. >> The test case is " gcc.c-torture/compile/pr27087.c", I observed it on >> aarch64-none-elf target when compiling the test case with '-Os' flag. >> >> A quick check shows, the cfg has been changed, but the loop information >> is not updated. Thus the information about the number of basic block in >> a loop is not reliable. >> >> Could you please have a look? > > As I mentioned, when we collapse a conditional inside a loop, we may change > the # of nodes in a loop which edges are exit edges and possibly other > stuff. So we need to mark loops as needing fixups. > > Verified this fixes the aarch64-elf regression and did a bootstrap & > regression test on x86_64-linux-gnu. > > Installed on the trunk. > > jeff > > commit 992d281b2d1ba53a49198db44fee92a505e16f5d > Author: Jeff Law <l...@tor.usersys.redhat.com> > Date: Fri Oct 2 15:22:04 2015 -0400 > > Re: [PATCH] Improve DOM's optimization of control statements > > * tree-ssa-dom.c (optimize_stmt): Note when loop structures need > fixups. > > diff --git a/gcc/ChangeLog b/gcc/ChangeLog > index 3f7561a..e541df3 100644 > --- a/gcc/ChangeLog > +++ b/gcc/ChangeLog > @@ -1,3 +1,8 @@ > +2015-10-02 Jeff Law <l...@redhat.com> > + > + * tree-ssa-dom.c (optimize_stmt): Note when loop structures need > + fixups. > + > 2015-10-02 Uros Bizjak <ubiz...@gmail.com> > > * system.h (ROUND_UP): New macro definition. > diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c > index a8b7038..d940816 100644 > --- a/gcc/tree-ssa-dom.c > +++ b/gcc/tree-ssa-dom.c > @@ -1843,6 +1843,12 @@ optimize_stmt (basic_block bb, gimple_stmt_iterator > si, > /* Delete threads that start at BB. */ > remove_jump_threads_starting_at (bb); > > + /* If BB is in a loop, then removing an outgoing edge from BB > + may cause BB to move outside the loop, changes in the > + loop exit edges, etc. So note that loops need fixing. */ > + if (bb_loop_depth (bb) > 0) > + loops_state_set (LOOPS_NEED_FIXUP); > +
I would rather do this in remove_ctrl_stmt_and_useless_edges and only if taken_edge is a loop exit. loop fixup is a pretty big hammer which we should avoid at all cost. So please try to be more specific on the cases you invoke it. Thanks, Richard. > /* Now clean up the control statement at the end of > BB and remove unexecutable edges. */ > remove_ctrl_stmt_and_useless_edges (bb, taken_edge->dest); >
