Hi!
As described in the PR, the r208165 change regressed following test.
The problem is that VRP inserts a useless ASSERT_EXPR right before
__builtin_unreachable () (obviously, the uses of the ASSERT_EXPR
lhs aren't and can't be used by anything), which then prevents
assert_unreachable_fallthru_edge_p from detecting it properly
(but, even ignoring ASSERT_EXPRs there still would fail, because
the ASSERT_EXPR adds another user of the SSA_NAME we check imm uses for).
Perhaps FOUND_IN_SUBGRAPH (4.3 and earlier era) would be always true
here, but live_on_edge provably isn't always true, so it makes sense to test
it, something that isn't live on the edge is useless.
The tree-cfg.c change is just small improvement discovered when looking into
it, clobber stmts before __builtin_unreachable can be certainly ignored,
they don't do anything.
The patch regresses ssa-ifcombine-10.c testcase, I'll post a fix for that
momentarily.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2014-03-11 Jakub Jelinek <ja...@redhat.com>
PR middle-end/60482
* tree-vrp.c (register_edge_assert_for_1): Don't add assert
if there are multiple uses, but op doesn't live on E edge.
* tree-cfg.c (assert_unreachable_fallthru_edge_p): Also ignore
clobber stmts before __builtin_unreachable.
* gcc.dg/vect/pr60482.c: New test.
--- gcc/tree-vrp.c.jj 2014-01-25 00:11:37.000000000 +0100
+++ gcc/tree-vrp.c 2014-03-10 14:59:03.748267354 +0100
@@ -5423,12 +5423,9 @@ register_edge_assert_for_1 (tree op, enu
return false;
/* We know that OP will have a zero or nonzero value. If OP is used
- more than once go ahead and register an assert for OP.
-
- The FOUND_IN_SUBGRAPH support is not helpful in this situation as
- it will always be set for OP (because OP is used in a COND_EXPR in
- the subgraph). */
- if (!has_single_use (op))
+ more than once go ahead and register an assert for OP. */
+ if (live_on_edge (e, op)
+ && !has_single_use (op))
{
val = build_int_cst (TREE_TYPE (op), 0);
register_new_assert_for (op, op, code, val, NULL, e, bsi);
--- gcc/tree-cfg.c.jj 2014-02-20 21:38:42.000000000 +0100
+++ gcc/tree-cfg.c 2014-03-10 14:59:52.058957446 +0100
@@ -410,9 +410,9 @@ assert_unreachable_fallthru_edge_p (edge
if (gsi_end_p (gsi))
return false;
stmt = gsi_stmt (gsi);
- if (is_gimple_debug (stmt))
+ while (is_gimple_debug (stmt) || gimple_clobber_p (stmt))
{
- gsi_next_nondebug (&gsi);
+ gsi_next (&gsi);
if (gsi_end_p (gsi))
return false;
stmt = gsi_stmt (gsi);
--- gcc/testsuite/gcc.dg/vect/pr60482.c.jj 2014-03-10 15:08:16.700085976
+0100
+++ gcc/testsuite/gcc.dg/vect/pr60482.c 2014-03-10 15:15:09.609738455 +0100
@@ -0,0 +1,20 @@
+/* PR middle-end/60482 */
+/* { dg-do compile } */
+/* { dg-additional-options "-Ofast" } */
+/* { dg-require-effective-target vect_int } */
+
+double
+foo (double *x, int n)
+{
+ double p = 0.0;
+ int i;
+ x = __builtin_assume_aligned (x, 128);
+ if (n % 128)
+ __builtin_unreachable ();
+ for (i = 0; i < n; i++)
+ p += x[i];
+ return p;
+}
+
+/* { dg-final { scan-tree-dump-not "epilog loop required" "vect" } } */
+/* { dg-final { cleanup-tree-dump "vect" } } */
Jakub
