| Message ID | CAMe9rOqun_xfN95S3US6wLoabMCQppyN9yg+DDk7U=PRR5fsGg@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
On Mon, May 2, 2016 at 9:25 PM, H.J. Lu <hjl.tools@gmail.com> wrote: > On Sat, Apr 30, 2016 at 2:28 PM, Patrick Palka <patrick@parcs.ath.cx> wrote: >> `On Fri, Apr 29, 2016 at 3:15 PM, Jeff Law <law@redhat.com> wrote: >>> On 04/19/2016 11:50 AM, Patrick Palka wrote: >>> >>>> 1. This patch introduces a "regression" in gcc.dg/tree-ssa/ssa-thread-11.c >>>> in that we no longer perform FSM threading during vrp2 but instead we >>>> detect two new jump threading opportunities during vrp1. Not sure if >>>> the new code is better but it is shorter. I wonder how this should be >>>> resolved... >>> >>> Definitely not a regression. As you note we thread two jumps earlier >>> utilizing your new code. With the old code we're dependent upon other >>> simplifications occurring which eventually exposes the FSM threads that the >>> test is checking for in vrp2. >>> >>> I think we just want to remove the test for FSM jump threads in VRP2. We get >>> coverage for your test via ssa-thread-14. That should just leave the >>> verification that we do not have irreducible loops at the end of VRP2 in >>> ssa-thread-11. I'll make that change. >>> >>> I do see what appears to be a missed jump thread, but that's not affected >>> positively or negatively by your change. There's a reasonable chance it's >>> only exposed by normal thread jumps in VRP2 and since we don't iterate, it's >>> left in the IL. I haven't analyzed it in detail, but my hope is that when I >>> pull the backwards threading out into its own pass that we'll start picking >>> up more of these secondary effects. >> >> Interesting info. I also spotted another minor optimization >> opportunity within this test case, although more related to vrp than >> to jump threading. It would require iterating over the use statements >> of a subexpression within a conditional, and it turns out that VRP >> already does this so it's only a matter of adding another case to test >> for during each iteration. I'll post a patch when it's ready. >> >>> >>> >>>> >>>> gcc/ChangeLog: >>>> >>>> * tree-ssa-threadedge.c (simplify_control_stmt_condition): Split >>>> out into ... >>>> (simplify_control_stmt_condition_1): ... here. Recurse into >>>> BIT_AND_EXPRs and BIT_IOR_EXPRs. >>>> >>>> gcc/testsuite/ChangeLog: >>>> >>>> * gcc.dg/tree-ssa/ssa-thread-14.c: New test. >>>> --- >>> >>> I fixed a few formatting nits (too long lines). >>> > > This one fails on Linux/x86-64 and Linux/x86. This patch fixes it. OK > for trunk? Ok. Richard. > > -- > H.J. > --- > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-14.c > b/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-14.c > index db9ed3b..e2ac2f7 100644 > --- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-14.c > +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-14.c > @@ -1,5 +1,5 @@ > /* { dg-do compile } */ > -/* { dg-additional-options "-O2 -fdump-tree-vrp" } */ > +/* { dg-additional-options "-O2 -fdump-tree-vrp-details" } */ > /* { dg-final { scan-tree-dump-times "Threaded jump" 8 "vrp1" } } */ > > void foo (void);
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-14.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-14.c index db9ed3b..e2ac2f7 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-14.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-thread-14.c @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-additional-options "-O2 -fdump-tree-vrp" } */ +/* { dg-additional-options "-O2 -fdump-tree-vrp-details" } */ /* { dg-final { scan-tree-dump-times "Threaded jump" 8 "vrp1" } } */ void foo (void);