On 10/02/2015 05:15 AM, Renlin Li wrote:
Hi Jeff,
Your patch causes an ICE regression.
The test case is " gcc.c-torture/compile/pr27087.c", I observed it on
aarch64-none-elf target when compiling the test case with '-Os' flag.
A quick check shows, the cfg has been changed, but the loop information
is not updated. Thus the information about the number of basic block in
a loop is not reliable.
Could you please have a look?
As I mentioned, when we collapse a conditional inside a loop, we may
change the # of nodes in a loop which edges are exit edges and possibly
other stuff. So we need to mark loops as needing fixups.
Verified this fixes the aarch64-elf regression and did a bootstrap &
regression test on x86_64-linux-gnu.
Installed on the trunk.
jeff
commit 992d281b2d1ba53a49198db44fee92a505e16f5d
Author: Jeff Law <l...@tor.usersys.redhat.com>
Date: Fri Oct 2 15:22:04 2015 -0400
Re: [PATCH] Improve DOM's optimization of control statements
* tree-ssa-dom.c (optimize_stmt): Note when loop structures need
fixups.
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 3f7561a..e541df3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2015-10-02 Jeff Law <l...@redhat.com>
+
+ * tree-ssa-dom.c (optimize_stmt): Note when loop structures need
+ fixups.
+
2015-10-02 Uros Bizjak <ubiz...@gmail.com>
* system.h (ROUND_UP): New macro definition.
diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index a8b7038..d940816 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -1843,6 +1843,12 @@ optimize_stmt (basic_block bb, gimple_stmt_iterator si,
/* Delete threads that start at BB. */
remove_jump_threads_starting_at (bb);
+ /* If BB is in a loop, then removing an outgoing edge from BB
+ may cause BB to move outside the loop, changes in the
+ loop exit edges, etc. So note that loops need fixing. */
+ if (bb_loop_depth (bb) > 0)
+ loops_state_set (LOOPS_NEED_FIXUP);
+
/* Now clean up the control statement at the end of
BB and remove unexecutable edges. */
remove_ctrl_stmt_and_useless_edges (bb, taken_edge->dest);
