[Bug middle-end/68870] [6 Regression] ICE on valid code at -O1, -O2 and -O3 on x86_64-linux-gnu

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68870

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot 
gnu.org

--- Comment #9 from Richard Biener <rguenth at gcc dot gnu.org> ---
So to complete my earlier fix we need to do sth like

Index: gcc/tree-cfgcleanup.c
===================================================================
--- gcc/tree-cfgcleanup.c       (revision 231673)
+++ gcc/tree-cfgcleanup.c       (working copy)
@@ -78,7 +78,8 @@ remove_fallthru_edge (vec<edge, va_gc> *
    at block BB.  */

 static bool
-cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi)
+cleanup_control_expr_graph (basic_block bb, gimple_stmt_iterator gsi,
+                           bool first_p)
 {
   edge taken_edge;
   bool retval = false;
@@ -95,15 +96,26 @@ cleanup_control_expr_graph (basic_block
       switch (gimple_code (stmt))
        {
        case GIMPLE_COND:
-         {
-           code_helper rcode;
-           tree ops[3] = {};
-           if (gimple_simplify (stmt, &rcode, ops, NULL, no_follow_ssa_edges,
-                                no_follow_ssa_edges)
-               && rcode == INTEGER_CST)
-             val = ops[0];
-           break;
-         }
+         /* During a first iteration on the CFG only remove trivially
+            dead edges but mark other conditions for re-evaluation.  */
+         if (first_p)
+           {
+             val = const_binop (gimple_cond_code (stmt), boolean_type_node,
+                                gimple_cond_lhs (stmt),
+                                gimple_cond_rhs (stmt));
+             if (! val)
+               bitmap_set_bit (cfgcleanup_altered_bbs, bb->index);
+           }
+         else
+           {
+             code_helper rcode;
+             tree ops[3] = {};
+             if (gimple_simplify (stmt, &rcode, ops, NULL,
no_follow_ssa_edges,
+                                  no_follow_ssa_edges)
+                 && rcode == INTEGER_CST)
+               val = ops[0];
+           }
+         break;

        case GIMPLE_SWITCH:
          val = gimple_switch_index (as_a <gswitch *> (stmt));
@@ -176,7 +188,7 @@ cleanup_call_ctrl_altering_flag (gimple
    true if anything changes.  */

 static bool
-cleanup_control_flow_bb (basic_block bb)
+cleanup_control_flow_bb (basic_block bb, bool first_p)
 {
   gimple_stmt_iterator gsi;
   bool retval = false;
@@ -199,7 +211,7 @@ cleanup_control_flow_bb (basic_block bb)
       || gimple_code (stmt) == GIMPLE_SWITCH)
     {
       gcc_checking_assert (gsi_stmt (gsi_last_bb (bb)) == stmt);
-      retval |= cleanup_control_expr_graph (bb, gsi);
+      retval |= cleanup_control_expr_graph (bb, gsi, first_p);
     }
   else if (gimple_code (stmt) == GIMPLE_GOTO
           && TREE_CODE (gimple_goto_dest (stmt)) == ADDR_EXPR
@@ -680,7 +692,7 @@ cleanup_tree_cfg_1 (void)
     {
       bb = BASIC_BLOCK_FOR_FN (cfun, i);
       if (bb)
-       retval |= cleanup_control_flow_bb (bb);
+       retval |= cleanup_control_flow_bb (bb, true);
     }

   /* After doing the above SSA form should be valid (or an update SSA
@@ -708,7 +720,7 @@ cleanup_tree_cfg_1 (void)
       if (!bb)
        continue;

-      retval |= cleanup_control_flow_bb (bb);
+      retval |= cleanup_control_flow_bb (bb, false);
       retval |= cleanup_tree_cfg_bb (bb);
     }