On Wed, 11 May 2016, Richard Biener wrote:
> On Tue, 10 May 2016, Richard Biener wrote:
>
> >
> > ifcvt is confused about fake edges not being loop exits which the
> > following fixes.
> >
> > Bootstrap / regtest pending on x86_64-unknown-linux-gnu.
>
> Didn't fare well. The following patch mitigates the issue as well
> but in the end make it just latent - it is still sth I wanted
> to persue anyway seeing the sometimes odd choices for added
> fake edges. The patch reduces the number from two to one
> and adds it to the real dead-end infinite loop only for the
> testcases.
>
> 2016-05-11 Richard Biener <rguent...@suse.de>
>
> PR tree-optimization/70986
> * cfganal.c (dfs_find_deadend): Prefer to take edges exiting
> loops.
>
> * gcc.dg/torture/pr70986-1.c: New testcase.
> * gcc.dg/torture/pr70986-2.c: Likewise.
> * gcc.dg/torture/pr70986-3.c: Likewise.
>
> Index: gcc/testsuite/gcc.dg/torture/pr70986-1.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/torture/pr70986-1.c (revision 0)
> +++ gcc/testsuite/gcc.dg/torture/pr70986-1.c (working copy)
> @@ -0,0 +1,22 @@
> +/* { dg-do compile } */
> +
> +int a, g;
> +char b, c;
> +short d, e, f;
> +
> +char
> +fn1 ()
> +{
> + return a ? a : 1;
> +}
> +
> +void
> +fn2 ()
> +{
> + char h;
> + for (; d;)
> + for (; e; e++)
> + c = (fn1 () && h) & !(f |= 9 ^ (b > (g = c)));
> + for (;;)
> + ;
> +}
> Index: gcc/testsuite/gcc.dg/torture/pr70986-2.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/torture/pr70986-2.c (revision 0)
> +++ gcc/testsuite/gcc.dg/torture/pr70986-2.c (working copy)
> @@ -0,0 +1,20 @@
> +/* { dg-do compile } */
> +
> +int gi, dg;
> +
> +void
> +fe (void)
> +{
> + int ka = gi;
> +
> + for (;;)
> + {
> + if (ka != 0)
> + {
> + if (dg != 0)
> + gi = 0;
> + ++ka;
> + }
> + ++dg;
> + }
> +}
> Index: gcc/testsuite/gcc.dg/torture/pr70986-3.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/torture/pr70986-3.c (revision 0)
> +++ gcc/testsuite/gcc.dg/torture/pr70986-3.c (working copy)
> @@ -0,0 +1,18 @@
> +/* { dg-do compile } */
> +
> +int a, b;
> +int
> +fn1 (int p1)
> +{
> + return p1 < 0 ? p1 : a;
> +}
> +
> +void
> +fn2 ()
> +{
> +lbl_100:
> + b = 1;
> + for (; b != 21; b = fn1 (b))
> + ;
> + goto lbl_100;
> +}
> Index: gcc/cfganal.c
> ===================================================================
> *** gcc/cfganal.c (revision 236069)
> --- gcc/cfganal.c (working copy)
> *************** dfs_find_deadend (basic_block bb)
> *** 747,753 ****
> return bb;
> }
>
> ! bb = EDGE_SUCC (bb, 0)->dest;
> }
>
> gcc_unreachable ();
> --- 751,771 ----
> return bb;
> }
>
> ! /* If we are in an analyzed cycle make sure to try exiting it.
> ! Note this is a heuristic only and expected to work when loop
> ! fixup is needed as well. */
> ! if (! bb->loop_father
> ! || ! loop_outer (bb->loop_father))
> ! bb = EDGE_SUCC (bb, 0)->dest;
> ! else
> ! {
> ! edge_iterator ei;
> ! edge e;
> ! FOR_EACH_EDGE (e, ei, bb->succs)
> ! if (bb->loop_father != e->dest->loop_father)
Actually I'll test using loop_exit_edge_p (bb->loop_father, e) as the
above may choose to enter a subloop.
Richard.
