Re: Wrong mappin of registers in location lists

[Daniel Berlin <dberlin at dberlin dot org>]

On Fri, 14 Feb 2003, Josef Zlomek wrote:

> > > as far as I can see gcc outputs wrong information to .debug_loc on
> > > x86-64. This is the assembler output:
> > >
> > > main:
> > > .LVL22:
> > >         pushq   %rbx
> > >         movl    %edi, %ebx
> > > .LVL23:
> > >         leal    1(%rbx), %edi
> > >         subq    $416, %rsp
> > > [...]
> > >
> > > This is DIE of argc:
> > >         .uleb128 0x3    # (DIE (0xef) DW_TAG_formal_parameter)
> > >         .long   .LASF4  # DW_AT_name: "argc"
> > >         .byte   0x1     # DW_AT_decl_file
> > >         .byte   0x17    # DW_AT_decl_line
> > >         .long   0x8f    # DW_AT_type
> > >         .long   .LLST3-.Ldebug_loc0     # DW_AT_location
> > >
> > > And finally location list of argc:
> > > .LLST3:
> > >         .quad   .LVL22-.text    # Location list begin address (*.LLST3)
> > >         .quad   .LVL23-.text    # Location list end address (*.LLST3)
> > >         .value  0x1     # Location expression size
> > >         .byte   0x55    # DW_OP_reg5
> > >         .quad   .LVL23-.text    # Location list begin address (*.LLST3)
> > >         .quad   .LFE7-.text     # Location list end address (*.LLST3)
> > >         .value  0x1     # Location expression size
> > >         .byte   0x53    # DW_OP_reg3
> > >         .quad   0x0     # Location list terminator begin (*.LLST3)
> > >         .quad   0x0     # Location list terminator end (*.LLST3)
> > >
> > > At the entry of the function (.LVL22), argc is dwarf2 register 5
> > > (DW_OP_reg5), ie %rdi on x86-64. From .LVL23 on it is saved in %rbx, ie.
> > > DW_OP_reg1. However debug information says it's in DW_OP_reg3, ie. %rdx.
> >
> > I do not know the register numbers for dwarf, but in gcc core the numbering is this:
> >
> > (from gcc/gcc/config/i386/i386.h:)
>
> And of course with 64-bit registers:
>
> #define ADDITIONAL_REGISTER_NAMES \
> { { "eax", 0 }, { "edx", 1 }, { "ecx", 2 }, { "ebx", 3 },       \
>   { "esi", 4 }, { "edi", 5 }, { "ebp", 6 }, { "esp", 7 },       \
>   { "rax", 0 }, { "rdx", 1 }, { "rcx", 2 }, { "rbx", 3 },       \
>   { "rsi", 4 }, { "rdi", 5 }, { "rbp", 6 }, { "rsp", 7 },       \
>   { "al", 0 }, { "dl", 1 }, { "cl", 2 }, { "bl", 3 },           \
>   { "ah", 0 }, { "dh", 1 }, { "ch", 2 }, { "bh", 3 },           \
>   { "mm0", 8},  { "mm1", 9},  { "mm2", 10}, { "mm3", 11},       \
>   { "mm4", 12}, { "mm5", 13}, { "mm6", 14}, { "mm7", 15} }
>
> I do not know whether the numbering is wrong or not.

However, we do know that the loclist is right, given this information.

The numbering says rbx == DW_OP_reg3, which is what we output.

>
> Josef
>