108 lines
4.1 KiB
Plaintext
108 lines
4.1 KiB
Plaintext
-*- text -*-
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PORTING:
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Sorry, no description of the interfaces is written up yet. Look at existing
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back ends and work from there.
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New hosts: The configure script, which is generated by autoconf,
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should handle all host specific configuration.
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New target formats: Look at the BFD_ASSEMBLER code. The a.out or ELF
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code might be a fair example. There are no "good" examples yet,
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unfortunately, nor any good documentation of the changes.
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New target processors: Check first to see if the BFD_ASSEMBLER interface is
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supported by the file format code you need to use.
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DOCUMENTATION:
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The internals of gas need documenting.
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The documentation should also contain a "Trouble" section similar to gcc's
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manual: real bugs, common problems, incompatibilities, etc.
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Anyone want to offer to maintain a man page?
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BFD CONVERSION:
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The "#ifdef BFD_ASSEMBLER" code is on its way in; the "#ifndef BFD_ASSEMBLER"
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code is on its way out. The new code uses BFD data structures, and calls BFD
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for anything that needs to be written to the output file. The old code did all
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the writing itself, or in a couple of cases, used BFD as a slightly higher
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level than stdio (i.e., bfd_seek, bfd_write -- these are not the preferred
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interface).
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Because of this, some of this code is messy. Lots of ifdef's, and the
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non-BFD_ASSEMBLER version often has multiple conditional tests inside it for
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various processors or formats. As the various targets get converted over,
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these will gradually go away.
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TO DO:
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Remove DONTDEF code, commented-out code.
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Eliminate, as much as possible, anything not in config that is conditionalized
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on a CPU, format, or environment.
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Merge COFF support into one version, supporting all the pseudo-ops used in
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either versions now, but using BFD for high-level operations. (See second
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following item.) Currently there are two versions (plus the new BFD code),
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which support different features, and are used on different targets.
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Convert remaining a.out/b.out targets to using the BFD_ASSEMBLER code by
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default.
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Finish conversion to using BFD for all object file writing. (This is the
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BFD_ASSEMBLER code, not BFD or BFD_HEADERS.) VMS might be the tough one here,
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since there's no BFD support for it at all yet. Eliminate the old code. Some
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of this can be done target by target, so doing a target where the CPU or
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format already supports BFD_ASSEMBLER mode may be easiest.
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Fix lots of uses of empty strings to use null pointers. Will improve
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efficiency, and should make code clearer too.
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Clean up comments; lots of 'em are one previous maintainer griping about
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another previous maintainer, unrelated to the code. (And with no names,
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they're not so fun to read. :-)
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For sparc: "call 0" becomes "jmpl %g0,%l7", and similarly for absolute
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addresses in -4096...4095. (Solaris assembler does this. No
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relocation required, no absolute symbol needed.) For addresses
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outside the range, for COFF, keep generating an absolute symbol to use
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for relocs.
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Get Steve to document H8/500 stuff (and others).
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Improve test suite. Incorporate more reported net bugs, and non-confidential
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Cygnus customer bugs, and anything else.
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Add support for i386/i486 16-bit mode, so operating system initialization code
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doesn't require a separate assembler nor lots of `.byte' directives.
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See if it's more maintainable (and not too much of a performance loss) to use
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a yacc grammar for parsing input. The lexer will have to be flexible, and the
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grammar will have to contain any construct used on any platform, but it may be
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easier to maintain, instead of having code in most of the back ends.
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PIC support.
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Torbjorn Granlund <tege@cygnus.com> writes, regarding alpha .align:
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Please make sure the .align directive works as in digital's assembler.
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They fill the space with a sequence of "bis $31,$31,$31;ldq_u $31,0($30)"
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since these two instructions can dual-issue. Since .align is ued a lot by
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gcc, it is an important optimization.
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(From old "NOTES" file to-do list, not really reviewed:)
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fix relocation types for i860, perhaps by adding a ref pointer to fixS?
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remove the ifdef's from fx_callj tests?
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space tighten sparc alignment?
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md_ => tc_
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share b.out with a.out.
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