[PATCH] Fix devirtualization ICE (PR tree-optimization/59622)

[Jakub Jelinek]

Hi!

Setting gimple_call_set_fndecl of a random method call to
__bultin_unreachable can't work properly, the method call probably
passes in arguments that __builtin_unreachable doesn't expect, and if
the method call has LHS, we'll ICE, because __builtin_unreachable doesn't
have a LHS.  Fixed by not doing anything for fold_stmt_inplace and
for fold_stmt just adding a new __buitin_unreachable () call before the
method call, DCE will DTRT then and we don't have to bother with adding
some dummy stmt to set up the lhs etc.

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

2013-12-30  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/59622
        * gimple-fold.c (gimple_fold_call): Don't replace OBJ_TYPE_REF
        call fndecl with 0 possible targets with BUILT_IN_UNREACHABLE,
        instead only for !inplace add a __builtin_unreachable () call
        before the call.

        * g++.dg/opt/pr59622.C: New test.

--- gcc/gimple-fold.c.jj        2013-12-18 17:32:59.000000000 +0100
+++ gcc/gimple-fold.c   2013-12-30 11:36:38.093211391 +0100
@@ -1184,13 +1184,19 @@ gimple_fold_call (gimple_stmt_iterator *
            = possible_polymorphic_call_targets (callee, &final);
          if (final && targets.length () <= 1)
            {
-             tree fndecl;
              if (targets.length () == 1)
-               fndecl = targets[0]->decl;
-             else
-               fndecl = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
-             gimple_call_set_fndecl (stmt, fndecl);
-             changed = true;
+               {
+                 gimple_call_set_fndecl (stmt, targets[0]->decl);
+                 changed = true;
+               }
+             else if (!inplace)
+               {
+                 tree fndecl = builtin_decl_implicit (BUILT_IN_UNREACHABLE);
+                 gimple new_stmt = gimple_build_call (fndecl, 0);
+                 gimple_set_location (new_stmt, gimple_location (stmt));
+                 gsi_insert_before (gsi, new_stmt, GSI_SAME_STMT);
+                 return true;
+               }
            }
        }
     }
--- gcc/testsuite/g++.dg/opt/pr59622.C.jj       2013-12-30 11:44:04.934893747 
+0100
+++ gcc/testsuite/g++.dg/opt/pr59622.C  2013-12-30 11:43:38.000000000 +0100
@@ -0,0 +1,19 @@
+// PR tree-optimization/59622
+// { dg-do compile }
+// { dg-options "-O2" }
+
+namespace
+{
+  struct A
+  {
+    virtual int foo ();
+    int bar () { return foo (); }
+  };
+}
+
+int
+baz ()
+{
+  A a;
+  return a.bar ();
+}

        Jakub