[PATCH] Don't ICE trying to redirect abnormal edges during shrink-wrapping (PR rtl-optimization/51495)

[Jakub Jelinek]

Hi!

On this testcase we ICE starting from
http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=181188
because one of the basic blocks we add to bb_tail has EDGE_ABNORMAL
edge (computed goto) from a basic block that doesn't need prologue.
We try to duplicate the basic block and finally redirect that EDGE_ABNORMAL
edge, which ICEs.

Fixed by not putting basic blocks into bb_tail if they have complex edges
from basic blocks that don't need prologue.
In x8_64/i686 bootstraps/regtests this only affected compile/pr51495.c,
compile/pr28489.c, torture/pr42462.C and execute/980526-1.c testcases.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2011-12-12  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/51495
        * function.c (thread_prologue_and_epilogue_insns): Don't add
        to bb_tail basic blocks that have EDGE_COMPLEX predecessor edges
        from basic blocks not needing prologue.

        * gcc.c-torture/compile/pr51495.c: New test.

--- gcc/function.c.jj   2011-12-11 22:02:37.000000000 +0100
+++ gcc/function.c      2011-12-12 14:31:01.821624702 +0100
@@ -5956,9 +5956,22 @@ thread_prologue_and_epilogue_insns (void
          FOR_EACH_EDGE (e, ei, tmp_bb->preds)
            if (single_succ_p (e->src)
                && !bitmap_bit_p (&bb_on_list, e->src->index)
-               && can_duplicate_block_p (e->src)
-               && bitmap_set_bit (&bb_tail, e->src->index))
-             VEC_quick_push (basic_block, vec, e->src);
+               && can_duplicate_block_p (e->src))
+             {
+               edge pe;
+               edge_iterator pei;
+
+               /* If there is predecessor of e->src which doesn't
+                  need prologue and the edge is complex,
+                  we might not be able to redirect the branch
+                  to a copy of e->src.  */
+               FOR_EACH_EDGE (pe, pei, e->src->preds)
+                 if ((pe->flags & EDGE_COMPLEX) != 0
+                     && !bitmap_bit_p (&bb_flags, pe->src->index))
+                   break;
+               if (pe == NULL && bitmap_set_bit (&bb_tail, e->src->index))
+                 VEC_quick_push (basic_block, vec, e->src);
+             }
        }
 
       /* Now walk backwards from every block that is marked as needing
--- gcc/testsuite/gcc.c-torture/compile/pr51495.c.jj    2011-12-12 
14:32:45.047017210 +0100
+++ gcc/testsuite/gcc.c-torture/compile/pr51495.c       2011-12-12 
14:32:15.000000000 +0100
@@ -0,0 +1,14 @@
+/* PR rtl-optimization/51495 */
+
+void bar (void);
+
+int
+foo (int i)
+{
+  static const void *const table[] = { &&begin, &&end };
+  goto *(table[i]);
+begin:
+  bar ();
+end:
+  return 0;
+}

        Jakub