[PATCH] Handle C++ x ? y : throw 1 COND_EXPRs in shortcut_cond_r (PR c++/49165)

[Jakub Jelinek]

Hi!

The C++ FE creates COND_EXPRs which have non-void type
and the same type on one of the arms, but the other arm
is THROW_EXPR (which has void type).
gimplify_cond_expr knows how to gimplify this, but shortcut_cond_r
tried to optimize
if (a ? b : throw 1) goto yes; else goto no;
into
if (a)
  if (b) goto yes; else goto no;
else
  if (throw 1) goto yes; else goto no;
which ICEs or errors out.  Fixed by not trying to optimize
such COND_EXPRs.  Bootstrapped/regtested on x86_64-linux and
i686-linux, committed to trunk/4.6 so far.

2011-05-26  Jakub Jelinek  <ja...@redhat.com>

        PR c++/49165
        * gimplify.c (shortcut_cond_r): Don't special case
        COND_EXPRs if they have void type on one of their arms.

        * g++.dg/eh/cond5.C: New test.

--- gcc/gimplify.c.jj   2011-05-20 08:14:08.000000000 +0200
+++ gcc/gimplify.c      2011-05-26 09:12:54.000000000 +0200
@@ -2573,7 +2573,9 @@ shortcut_cond_r (tree pred, tree *true_l
                           new_locus);
       append_to_statement_list (t, &expr);
     }
-  else if (TREE_CODE (pred) == COND_EXPR)
+  else if (TREE_CODE (pred) == COND_EXPR
+          && !VOID_TYPE_P (TREE_TYPE (TREE_OPERAND (pred, 1)))
+          && !VOID_TYPE_P (TREE_TYPE (TREE_OPERAND (pred, 2))))
     {
       location_t new_locus;
 
@@ -2581,7 +2583,10 @@ shortcut_cond_r (tree pred, tree *true_l
         if (a)
           if (b) goto yes; else goto no;
         else
-          if (c) goto yes; else goto no;  */
+          if (c) goto yes; else goto no;
+
+        Don't do this if one of the arms has void type, which can happen
+        in C++ when the arm is throw.  */
 
       /* Keep the original source location on the first 'if'.  Set the source
         location of the ? on the second 'if'.  */
--- gcc/testsuite/g++.dg/eh/cond5.C.jj  2011-05-26 09:15:24.000000000 +0200
+++ gcc/testsuite/g++.dg/eh/cond5.C     2011-05-26 09:07:16.000000000 +0200
@@ -0,0 +1,43 @@
+// PR c++/49165
+// { dg-do run }
+
+extern "C" void abort ();
+
+int
+foo (bool x, int y)
+{
+  if (y < 10 && (x ? true : throw 1))
+    y++;
+  if (y > 20 || (x ? true : throw 2))
+    y++;
+  return y;
+}
+
+int
+main ()
+{
+  if (foo (true, 0) != 2
+      || foo (true, 10) != 11
+      || foo (false, 30) != 31)
+    abort ();
+  try
+    {
+      foo (false, 0);
+      abort ();
+    }
+  catch (int i)
+    {
+      if (i != 1)
+       abort ();
+    }
+  try
+    {
+      foo (false, 10);
+      abort ();
+    }
+  catch (int i)
+    {
+      if (i != 2)
+       abort ();
+    }
+}

        Jakub