On December 30, 2017 8:42:06 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>The problem on this testcase is that ldist pass changes some
>GIMPLE_CONDs
>into 0 != 0 or similar, but the pass doesn't perform any cleanups, then
>ifcvt is run and does completely useless work of duplicating dead loops
>and guarding them with LOOP_VECTORIZED ifns, and then during the ifcvt
>cfg cleanup the dead loops are optimized away, but nothing removes the
>corresponding LOOP_VECTORIZED ifns. While perhaps we'll need to hook
>into
>the loop removal and remove the dead ifns or remove the dead ifns
>during
>vectorizer pass using a more expensive way at some point (e.g. by
>scanning
>all bb's last insn for GIMPLE_COND checking LOOP_VECTORIZED) at some
>point,
>in this case it seems to me clearly preferrable to let the ldist pass
>clean
>up after itself, so that we don't do useless work in ifcvt from the
>beginning.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
Richard.
>2017-12-30 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/83581
> * tree-loop-distribution.c (pass_loop_distribution::execute): Return
> TODO_cleanup_cfg if any changes have been made.
>
> * gcc.dg/pr83581.c: New test.
>
>--- gcc/tree-loop-distribution.c.jj 2017-12-21 09:43:17.486071696 +0100
>+++ gcc/tree-loop-distribution.c 2017-12-30 16:54:08.106143319 +0100
>@@ -3103,7 +3103,7 @@ pass_loop_distribution::execute (functio
>
> checking_verify_loop_structure ();
>
>- return 0;
>+ return changed ? TODO_cleanup_cfg : 0;
> }
>
> } // anon namespace
>--- gcc/testsuite/gcc.dg/pr83581.c.jj 2017-12-30 16:55:35.950164947
>+0100
>+++ gcc/testsuite/gcc.dg/pr83581.c 2017-12-30 16:55:17.520160406 +0100
>@@ -0,0 +1,21 @@
>+/* PR tree-optimization/83581 */
>+/* { dg-do compile } */
>+/* { dg-options "-O3 -fno-tree-copy-prop -fno-tree-loop-im" } */
>+
>+int a, b, c;
>+
>+int
>+foo (int x)
>+{
>+ int *d = &x;
>+ while (a < 1)
>+ {
>+ for (b = 0; b < 2; ++b)
>+ {
>+ *d += !!x + 1;
>+ d = &c;
>+ }
>+ ++a;
>+ }
>+ return *d;
>+}
>
> Jakub
