RFC: PR 19650

[Dale Johannesen]

This is due to a problem in folding.  fold() is given this:

<mult_expr 0x77d150
     type <integer_type 0x4240c400 long unsigned int public unsigned 
sizetype SI
     arg 0 <nop_expr 0x77fd80 type <integer_type 0x4240c400 long 
unsigned int>
         arg 0 <eq_expr 0x77dcf0 type <boolean_type 0x4240ca80 bool>
             arg 0 <var_decl 0x77a280>
             arg 1 <integer_cst 0x424dcda0 constant invariant 2>>>
     arg 1 <integer_cst 0x4240e380 4>>

which gets into the optimization in 
fold_binary_op_with_conditional_arg, which asks fold to do this:

  <mult_expr 0x73e180
     type <integer_type 0x4240c400 long unsigned int public unsigned 
sizetype SI
     constant invariant
     arg 0 <integer_cst 0x4240e9a0 type <boolean_type 0x4240ca80 bool> 
constant invariant 1>
     arg 1 <integer_cst 0x4240e380 4>>

which gets evaluated in type boolean, resulting in 0 rather than 4.  
I'm not sure where in the twisty
little passages this should be fixed, but 
fold_binary_op_with_conditional_arg is taking a type
from the EQ_EXPR, even though that should always be boolean (right)?  
Which is suspicious,
and I'm inclined to think it should be using the input type instead.  
Like this:

Index: fold-const.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/fold-const.c,v
retrieving revision 1.497
diff -u -d -b -w -p -r1.497 fold-const.c
--- fold-const.c        23 Jan 2005 15:05:29 -0000      1.497
+++ fold-const.c        27 Jan 2005 22:45:48 -0000
@@ -5412,10 +5412,10 @@ fold_binary_op_with_conditional_arg (enu
      }
    else
      {
-      tree testtype = TREE_TYPE (cond);
+      /*tree testtype = TREE_TYPE (cond);*/
        test = cond;
-      true_value = constant_boolean_node (true, testtype);
-      false_value = constant_boolean_node (false, testtype);
+      true_value = constant_boolean_node (true, /*test*/type);
+      false_value = constant_boolean_node (false, /*test*/type);
      }

    if (lhs == 0)

Does this look like the right approach?