gas/NOTES

   1 -*- text -*-
   2
   3 PORTING:
   4
   5 Sorry, no description of the interfaces is written up yet.  Look at existing
   6 back ends and work from there.
   7
   8 New hosts: The configure script, which is generated by autoconf,
   9 should handle all host specific configuration.
  10
  11 New target formats: Look at the BFD_ASSEMBLER code.  The a.out or ELF
  12 code might be a fair example.  There are no "good" examples yet,
  13 unfortunately, nor any good documentation of the changes.
  14
  15 New target processors: Check first to see if the BFD_ASSEMBLER interface is
  16 supported by the file format code you need to use.
  17
  18 DOCUMENTATION:
  19
  20 The internals of gas need documenting.
  21
  22 The documentation should also contain a "Trouble" section similar to gcc's
  23 manual: real bugs, common problems, incompatibilities, etc.
  24
  25 Anyone want to offer to maintain a man page?
  26
  27 BFD CONVERSION:
  28
  29 The "#ifdef BFD_ASSEMBLER" code is on its way in; the "#ifndef BFD_ASSEMBLER"
  30 code is on its way out.  The new code uses BFD data structures, and calls BFD
  31 for anything that needs to be written to the output file.  The old code did all
  32 the writing itself, or in a couple of cases, used BFD as a slightly higher
  33 level than stdio (i.e., bfd_seek, bfd_write -- these are not the preferred
  34 interface).
  35
  36 Because of this, some of this code is messy.  Lots of ifdef's, and the
  37 non-BFD_ASSEMBLER version often has multiple conditional tests inside it for
  38 various processors or formats.  As the various targets get converted over,
  39 these will gradually go away.
  40
  41 TO DO:
  42
  43 Remove DONTDEF code, commented-out code.
  44
  45 Eliminate, as much as possible, anything not in config that is conditionalized
  46 on a CPU, format, or environment.
  47
  48 Merge COFF support into one version, supporting all the pseudo-ops used in
  49 either versions now, but using BFD for high-level operations.  (See second
  50 following item.)  Currently there are two versions (plus the new BFD code),
  51 which support different features, and are used on different targets.
  52
  53 Convert remaining a.out/b.out targets to using the BFD_ASSEMBLER code by
  54 default.
  55
  56 Finish conversion to using BFD for all object file writing.  (This is the
  57 BFD_ASSEMBLER code, not BFD or BFD_HEADERS.)  VMS might be the tough one here,
  58 since there's no BFD support for it at all yet.  Eliminate the old code.  Some
  59 of this can be done target by target, so doing a target where the CPU or
  60 format already supports BFD_ASSEMBLER mode may be easiest.
  61
  62 Fix lots of uses of empty strings to use null pointers.  Will improve
  63 efficiency, and should make code clearer too.
  64
  65 Clean up comments; lots of 'em are one previous maintainer griping about
  66 another previous maintainer, unrelated to the code.  (And with no names,
  67 they're not so fun to read. :-)
  68
  69 For sparc: "call 0" becomes "jmpl %g0,%l7", and similarly for absolute
  70 addresses in -4096...4095.  (Solaris assembler does this.  No
  71 relocation required, no absolute symbol needed.)  For addresses
  72 outside the range, for COFF, keep generating an absolute symbol to use
  73 for relocs.
  74
  75 Get Steve to document H8/500 stuff (and others).
  76
  77 Improve test suite.  Incorporate more reported net bugs, and non-confidential
  78 Cygnus customer bugs, and anything else.
  79
  80 Add support for i386/i486 16-bit mode, so operating system initialization code
  81 doesn't require a separate assembler nor lots of `.byte' directives.
  82
  83 See if it's more maintainable (and not too much of a performance loss) to use
  84 a yacc grammar for parsing input.  The lexer will have to be flexible, and the
  85 grammar will have to contain any construct used on any platform, but it may be
  86 easier to maintain, instead of having code in most of the back ends.
  87
  88 PIC support.
  89
  90 Torbjorn Granlund <tege@cygnus.com> writes, regarding alpha .align:
  91
  92    Please make sure the .align directive works as in digital's assembler.
  93    They fill the space with a sequence of "bis $31,$31,$31;ldq_u $31,0($30)"
  94    since these two instructions can dual-issue.  Since .align is ued a lot by
  95    gcc, it is an important optimization.
  96
  97 (From old "NOTES" file to-do list, not really reviewed:)
  98
  99 fix relocation types for i860, perhaps by adding a ref pointer to fixS?
 100
 101 remove the ifdef's from fx_callj tests?
 102
 103 space tighten sparc alignment?
 104
 105 md_ => tc_
 106
 107 share b.out with a.out.