[Bug java/64044] New: Java emits bogus .class$ decls

["rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64044

            Bug ID: 64044
           Summary: Java emits bogus .class$ decls
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: java
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rguenth at gcc dot gnu.org
                CC: aph at gcc dot gnu.org

Currently the Java FE is lucky that not all -findirect-dispatch testcases are
miscompiled as gimple-fold.c:get_symbol_constant_value has

      /* Variables declared 'const' without an initializer
         have zero as the initializer if they may not be
         overridden at link or run time.  */
      if (!val
          && (INTEGRAL_TYPE_P (TREE_TYPE (sym))
               || SCALAR_FLOAT_TYPE_P (TREE_TYPE (sym))))
        return build_zero_cst (TREE_TYPE (sym));

which for unkown reason avoids to fold the reads from .class$ at the beginning
of all functions to NULL (because the above doesn't allow pointer types).

I ran into this when doing the same during value-numbering but "forgetting"
to paper over the Java FE bug.

The Java FE emits (for example)

 <var_decl 0x7ffff6c6e360 Array_2.class$
    type <pointer_type 0x7ffff6c69a80
        type <record_type 0x7ffff6c69930 java.lang.Class readonly type_4 BLK
            size <integer_cst 0x7ffff6c43858 constant 2240>
            unit size <integer_cst 0x7ffff6c43828 constant 280>
            align 64 symtab 0 alias set -1 canonical type 0x7ffff6c69930 fields
<field_decl 0x7ffff6c521c8 D.89>
            pointer_to_this <pointer_type 0x7ffff6c699d8>>
        readonly public unsigned DI
        size <integer_cst 0x7ffff6c25bb8 constant 64>
        unit size <integer_cst 0x7ffff6c25bd0 constant 8>
        align 64 symtab 0 alias set -1 canonical type 0x7ffff6c69a80
        pointer_to_this <pointer_type 0x7ffff6c7f888>>
    readonly constant addressable public static unsigned ignored DI file
Array_2.java line 4 col 0 size <integer_cst 0x7ffff6c25bb8 64> unit size
<integer_cst 0x7ffff6c25bd0 8>
    align 64 context <record_type 0x7ffff6c5e540 Array_2>
    (mem/u/f/c:DI (symbol_ref:DI ("_ZN7Array_27class$$E") [flags 0x2] 
<var_decl 0x7ffff6c6e360 Array_2.class$>) [2 Array_2.class$+0 S8 A64])>

which misses an initializer (it seems to be not initialized in .s either,
thus the flags on it are wrong?  Probably they get initialized by the
runtime?).