145 lines
5.5 KiB
Plaintext
145 lines
5.5 KiB
Plaintext
(This file is under construction.)
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The Code Pedigree of This Directory
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This directory contains a big merge of several development lines of
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gas as well as a few bug fixes and some configuration that I've added
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in order to retain my own sanity.
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A little history.
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The only common baseline of all versions was gas-1.31.
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From 1.31, Intel branched off and added:
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support for the Intel 80960 (i960) processor.
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support for b.out object files.
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some bug fixes.
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sloppy mac MPW support
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Intel gnu/960 makefiles and version numbering.
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Many of the bug fixes found their way into the main development line
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prior to 1.36. ALL intel changes were ifdef'd I80960. This was good
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as it isolated the changes, but bad in that it connected the b.out
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support to the i960 support, and bad in that the bug fixes were only
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active in the i960+b.out executables of gas, (although most of these
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were nicely marked with comments indicating that they were probably
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general bug fixes.)
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To pick up the main FSF development line again, along the way to 1.36,
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several new processors were added, many bugs fixed, and the world was
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a somewhat better place in general.
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From gas-1.36, Loic at Axis Design (france!) encapsulated object
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format specific actions, added coff versions of those encapsulations,
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and a config.gas style configuration and Makefile. This was a big
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change and a lot of work.
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Then along came the FIRST FSF release of gas-1.37. I say this because
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there have been at least two releases of gas-1.37. Only two of them
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do we care about for this story, so let's call them gas-1.37.1 and
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gas-1.37.2.
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Here starts the confusion. Firstly, gas-1.37.1 did not compile.
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In the meantime, John Gilmore at Cygnus Support had been hacking
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gas-1.37.1. He got it to compile. He added support for the AMD 29000
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processor. AND he started encapsulating some of the a.out specific
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pieces of code mostly into functions. AND he rebuilt the relocation
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info to be generic. AND he restructured somewhat so that for a single
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host, cross assemblers could be built for all targets in the same
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directory. Useful work but a considerable nuisance because the a29k
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changes were not partitioned from the encapsulation changes, the
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encapsulation changes were incomplete, and the encapsulation required
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functions where alternate structuring might have used macros. Let's
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call this version gas-1.37.1+a29k.
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By the time gas-1.37.2 was "released", (remember that it TOO was
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labelled by FSF as gas-1.37), it compiled, but it also added i860
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support and ansi style const declarations.
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At this point, Loic rolled his changes into gas-1.37.2.
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What I've done.
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I collected all the stray versions of gas that sounded relevant to my
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goals of cross assembly and alternate object file formats and the FSF
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releases from which the stray versions had branched.
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I rolled the Intel i960 changes from 1.31 into versions that I call
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1.34+i960, 1.36+i960, and then 1.37.1+i960.
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Then I merged 1.37.1+i960 with 1.37.1+a29k to produce what I call
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1.37.1+i960+a29k or 1.37.3.
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From 1.37.3, I pulled in Loic's stuff. This wasn't easy as Loic's
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stuff hit all the same points as John's encapsulations. Loic's goal
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was to split the a.out from coff dependancies for native assembly on
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coff, while John's was to split for multiple cross assembly from a
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single host.
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Loic's config arranged files much like emacs into m-*, etc. I've
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rearranged these somewhat.
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Theory:
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The goal of the new configuration scheme is to bury all object format,
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target processor, and host machine dependancies in object, target, and
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host specific files. That is, to move all #ifdef's out of the gas
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common code.
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Here's how it works. There is a .h and a .c file for each object file
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format, a .h and a .c file for each target processor, and a .h for
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each host. config.gas creates {sym}links in the current directory to
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the appropriate files in the config directory. config.gas also serves
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as a list of triplets {host, target, object-format} that have been
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tested at one time or another. I also recommend that config.gas be
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used to document triplet specific notes as to purpose of the triplet,
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etc.
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Implementation:
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host.h is a {sym}link to .../config/xm-yourhost.h. It is intended to
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be used to hide host compiler, system header file, and system library
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differences between host machines. If your host needs actual c source
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files, then either: these are generally useful functions, in which
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case you should probably build a local library outside of the gas
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source tree, or someone, perhaps me, is confused about what is needed
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by different hosts.
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obj-format.h is a {sym}link to .../config/obj-something.h. It is intended
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All gas .c files include as.h.
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as.h #define's "gas", includes host.h, defines a number of gas
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specific structures and types, and then includes tp.h, obj.h, and
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target-environment.h.
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target-environment.h defines a target environment specific
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preprocessor flag, eg, TE_SUN, and then includes obj-format.h.
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obj-format.h defines an object format specific preprocessor flag, eg,
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OBJ_AOUT, OBJ_BOUT, OBJ_COFF, includes "target-processor.h", and then
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defines the object specific macros, functions, types, and structures.
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target-processor.h
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target-processor.
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Porting:
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There appear to be four major types of ports; new hosts, new target
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processors, new object file formats, and new target environments.
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-----
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reloc now stored internally as generic. (symbols too?) (segment types
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vs. names?)
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I don't mean to overlook anyone here. There have also been several
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other development lines here that I looked at and elected to bypass.
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Specifically, xxx's stabs in coff stuff was particularly tempting.
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