[PATCH] Add verifier for virtual SSA form

[Richard Biener <rguenther at suse dot de>]

This adds a verifier that makes sure no overlapping life-ranges occur
for virtuals.

Bootstrap and regtest running on x86_64-unknown-linux-gnu.

Richard.

2016-08-15  Richard Biener  <rguenther@suse.de>

	* tree-ssa.c: Include tree-cfg.h and tree-dfa.h.
	(verify_vssa): New function verifying virtual SSA form.
	(verify_ssa): Call it.

Index: gcc/tree-ssa.c
===================================================================
*** gcc/tree-ssa.c	(revision 239473)
--- gcc/tree-ssa.c	(working copy)
*************** along with GCC; see the file COPYING3.
*** 39,44 ****
--- 39,46 ----
  #include "tree-ssa.h"
  #include "cfgloop.h"
  #include "cfgexpand.h"
+ #include "tree-cfg.h"
+ #include "tree-dfa.h"
  
  /* Pointer map of variable mappings, keyed by edge.  */
  static hash_map<edge, auto_vec<edge_var_map> > *edge_var_maps;
*************** release_defs_bitset (bitmap toremove)
*** 603,608 ****
--- 605,669 ----
        }
  }
  
+ /* Verify virtual SSA form.  */
+ 
+ bool
+ verify_vssa (basic_block bb, tree current_vdef, sbitmap visited)
+ {
+   if (bitmap_bit_p (visited, bb->index))
+     return false;
+ 
+   bitmap_set_bit (visited, bb->index);
+ 
+   /* Pick up virtual PHI def.  */
+   gphi *phi = get_virtual_phi (bb);
+   if (phi)
+     current_vdef = gimple_phi_result (phi);
+ 
+   /* Verify stmts.  */
+   bool err = false;
+   for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi);
+        gsi_next (&gsi))
+     {
+       gimple *stmt = gsi_stmt (gsi);
+       tree vuse = gimple_vuse (stmt);
+       if (vuse)
+ 	{
+ 	  if (vuse != current_vdef)
+ 	    {
+ 	      error ("stmt with wrong VUSE %qD, expected %qD",
+ 		     vuse, current_vdef);
+ 	      print_gimple_stmt (stderr, stmt, 0, TDF_VOPS);
+ 	      err = true;
+ 	    }
+ 	  tree vdef = gimple_vdef (stmt);
+ 	  if (vdef)
+ 	    current_vdef = vdef;
+ 	}
+     }
+ 
+   /* Verify destination PHI uses and recurse.  */
+   edge_iterator ei;
+   edge e;
+   FOR_EACH_EDGE (e, ei, bb->succs)
+     {
+       gphi *phi = get_virtual_phi (e->dest);
+       if (phi
+ 	  && PHI_ARG_DEF_FROM_EDGE (phi, e) != current_vdef)
+ 	{
+ 	  error ("PHI node with wrong VUSE %qD, expected %qD",
+ 		 PHI_ARG_DEF_FROM_EDGE (phi, e), current_vdef);
+ 	  print_gimple_stmt (stderr, phi, 0, TDF_VOPS);
+ 	  err = true;
+ 	}
+ 
+       /* Recurse.  */
+       err |= verify_vssa (e->dest, current_vdef, visited);
+     }
+ 
+   return err;
+ }
+ 
  /* Return true if SSA_NAME is malformed and mark it visited.
  
     IS_VIRTUAL is true if this SSA_NAME was found inside a virtual
*************** verify_ssa (bool check_modified_stmt, bo
*** 1024,1029 ****
--- 1110,1125 ----
  
    free (definition_block);
  
+   if (gimple_vop (cfun)
+       && ssa_default_def (cfun, gimple_vop (cfun)))
+     {
+       auto_sbitmap visited (last_basic_block_for_fn (cfun) + 1);
+       bitmap_clear (visited);
+       if (verify_vssa (ENTRY_BLOCK_PTR_FOR_FN (cfun),
+ 		       ssa_default_def (cfun, gimple_vop (cfun)), visited))
+ 	goto err;
+     }
+ 
    /* Restore the dominance information to its prior known state, so
       that we do not perturb the compiler's subsequent behavior.  */
    if (orig_dom_state == DOM_NONE)