[Bug middle-end/54961] [4.8 Regression] FAIL: gfortran.dg/pr48757.f -O (internal compiler error) after revision 192440

["steven at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54961

--- Comment #2 from Steven Bosscher <steven at gcc dot gnu.org> 2012-10-19 21:57:54 UTC ---
Something I'm going to test:

Index: ira-lives.c
===================================================================
--- ira-lives.c (revision 192571)
+++ ira-lives.c (working copy)
@@ -1373,6 +1373,19 @@ process_bb_node_lives (ira_loop_tree_nod
       if (bb_has_abnormal_pred (bb))
        {
 #ifdef STACK_REGS
+         /* Mark all stack mode registers and stack hard registers live
+            so that they will conflict and allocation across the abnormal
+            edge is impossible.
+            Stack registers must be treated as live in the traditional,
+            DF_LR-like sense, because compensation code may have to be
+            introduced on edges.  The register allocator treats the stack
+            registers like all other, non-stack registers.  It doesn't
+            know that stack shuffling may be required and may allocate
+            a partially available stack reg in ways that result in the
+            need for compensation code on abnormal edges.  See PR54961.  */
+         EXECUTE_IF_SET_IN_BITMAP (DF_LR_IN (bb), FIRST_PSEUDO_REGISTER, j,
bi)
+           if (IS_STACK_MODE (GET_MODE (regno_reg_rtx[j])))
+             mark_pseudo_regno_live (j);
          EXECUTE_IF_SET_IN_SPARSESET (objects_live, px)
            { 
              ira_allocno_t a = OBJECT_ALLOCNO (ira_object_id_map[px]);