[Bug gdb/9977] New: DW_OP_piece used to specify underined part of location is ignored

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

I am trying to add support to GCC to track SRAed structures and for structure
where some fields are optimized out I am producing following die:

        .uleb128 0x15   # (DIE (0x347) DW_TAG_variable)
        .ascii "a\0"    # DW_AT_name
        .byte   0x1     # DW_AT_decl_file (t.c)
        .byte   0x11    # DW_AT_decl_line
        .long   0x318   # DW_AT_type
        .byte   0x8     # DW_AT_location
        .byte   0x93    # DW_OP_piece
        .uleb128 0x4
        .byte   0x56    # DW_OP_reg6
        .byte   0x93    # DW_OP_piece
        .uleb128 0x4
        .byte   0x50    # DW_OP_reg0
        .byte   0x93    # DW_OP_piece
        .uleb128 0x4
        .byte   0x0     # end of children of DIE 0x2e7

I believe this is correct and identical to example in Example Location
Expression of dwarf3 standard.
But I get the following error:
(gdb) p a
Asked for position 0 of stack, stack only has 0 elements on it.

-- 
           Summary: DW_OP_piece used to specify underined part of location
                    is ignored
           Product: gdb
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: gdb
        AssignedTo: unassigned at sourceware dot org
        ReportedBy: hubicka at gcc dot gnu dot org
                CC: gdb-prs at sourceware dot org
  GCC host triplet: x86_64-pc-linux-gnu


http://sourceware.org/bugzilla/show_bug.cgi?id=9977

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