On Mon, Jan 23, 2017 at 2:38 PM, Michael Matz <m...@suse.de> wrote:
> Hi,
>
> the loop structure in the testcase is funny enough to confuse loop
> splitting (it essentially would have been an irreducable region if it
> weren't for the fact that one entry edge is stopped with a builtin_trap;
> and so it transforms into a strangely rotated loop where latch and header
> aren't at the usual position). We need to compute the edge staying in the
> loop given the exit edge, which I was doing by looking at predecessor
> edges of the latch, and that wasn't working with the testcase. Of course
> there's an easier way: it's simply the edge out of exit->src that isn't
> exit itself :)
>
> So, patch fixes the testcase. Regstrapped on x86-64-linux with all
> languages+Ada, no regressions. Okay for trunk?
Ok.
Richard.
>
> Ciao,
> Michael.
>
> PR tree-optimization/78384
> * tree-ssa-loop-split.c (patch_loop_exit): Use correct edge.
>
> testsuite/
> PR tree-optimization/78384
> * gcc.dg/pr78384.c: New test.
>
> diff --git a/gcc/tree-ssa-loop-split.c b/gcc/tree-ssa-loop-split.c
> index 7809db0..f104b26 100644
> --- a/gcc/tree-ssa-loop-split.c
> +++ b/gcc/tree-ssa-loop-split.c
> @@ -159,7 +159,7 @@ patch_loop_exit (struct loop *loop, gcond *guard, tree
> nextval, tree newbound,
> nextval, newbound);
> update_stmt (stmt);
>
> - edge stay = single_pred_edge (loop->latch);
> + edge stay = EDGE_SUCC (exit->src, EDGE_SUCC (exit->src, 0) == exit);
>
> exit->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
> stay->flags &= ~(EDGE_TRUE_VALUE | EDGE_FALSE_VALUE);
> diff --git a/gcc/testsuite/gcc.dg/pr78384.c b/gcc/testsuite/gcc.dg/pr78384.c
> new file mode 100644
> index 0000000..d93437d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr78384.c
> @@ -0,0 +1,25 @@
> +/* PR tree-optimization/78384
> + { dg-do compile }
> + { dg-options "-O3 -w -fsplit-loops" } */
> +void
> +a2 (int wv, int yg, int r9)
> +{
> + while (wv < 1)
> + {
> + int vn = r9 % 0;
> +
> + while (yg < 1)
> + {
> + int lz;
> +
> + for (r9 = 0; r9 < 17; ++r9)
> + {
> + }
> +
> + it:
> + lz = (yg++ >= 0) ? 2 : 0;
> + wv = vn < lz;
> + }
> + }
> + goto it;
> +}
