[Bug sanitizer/83388] reference statement index not found error with -fsanitize=null

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83388

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-12-12
                 CC|                            |hubicka at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
Index: gcc/lto-streamer-in.c
===================================================================
--- gcc/lto-streamer-in.c       (revision 255578)
+++ gcc/lto-streamer-in.c       (working copy)
@@ -1175,6 +1175,16 @@ input_function (tree fn_decl, struct dat
            }
          if (remove)
            {
+             /* If we are asked to remove a non-debug stmt replace it
+                with a nop instead to not confuse IPA references that
+                might refer to the original.  */
+             if (! is_gimple_debug (stmt))
+               {
+                 gimple *nop = gimple_build_nop ();
+                 gimple_set_uid (nop, gimple_uid (stmt));
+                 gsi_insert_before (&bsi, nop, GSI_SAME_STMT);
+                 stmts[gimple_uid (nop)] = nop;
+               }
              gimple_stmt_iterator gsi = bsi;
              gsi_next (&bsi);
              unlink_stmt_vdef (stmt);

works to fix the ICE.  We'll end up with a "dangling" IPA reference but
hopefully that's safe...

The other option would be to remove those IPA references on-the-fly.

Honza, would it be safe to simply do

Index: gcc/lto-streamer-in.c
===================================================================
--- gcc/lto-streamer-in.c       (revision 255578)
+++ gcc/lto-streamer-in.c       (working copy)
@@ -921,8 +921,6 @@ fixup_call_stmt_edges_1 (struct cgraph_n
          fatal_error (input_location,
                       "Reference statement index out of range");
        ref->stmt = stmts[ref->lto_stmt_uid - 1];
-       if (!ref->stmt)
-         fatal_error (input_location, "Reference statement index not found");
       }
 }

instead?  Thus leave ref->stmt == NULL?  Or would it be safe to remove
the IPA reference at this stage (I suppose IPA transform phase might get
confused if they stream references to such references?)