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llvm-6502/lib/Target/IA64/README
Chris Lattner 52387be1e0 If a function is vararg, never pass inreg arguments in registers. Thanks to
Anton for half of this patch.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37641 91177308-0d34-0410-b5e6-96231b3b80d8
2007-06-19 00:13:10 +00:00

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*** README for the LLVM IA64 Backend "Version 0.01" - March 18, 2005
*** Quote for this version:
"Kaori and Hitomi are naughty!!"
Congratulations, you have found:
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* Bow down, bow down, before the power of IA64! Or be crushed, *
* be crushed, by its jolly registers of doom!! *
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DEVELOPMENT PLAN:
_ you are 2005 maybe 2005 2006 2006 and
/ here | | | beyond
v v v v |
v
CLEAN UP ADD INSTRUCTION ADD PLAY WITH
INSTRUCTION --> SCHEDULING AND --> JIT --> DYNAMIC --> FUTURE WORK
SELECTION BUNDLING SUPPORT REOPTIMIZATION
DISCLAIMER AND PROMISE:
As of the time of this release, you are probably better off using Intel C/C++
or GCC. The performance of the code emitted right now is, in a word,
terrible. Check back in a few months - the story will be different then,
I guarantee it.
TODO:
- stop passing FP args in both FP *and* integer regs when not required
- allocate low (nonstacked) registers more aggressively
- clean up and thoroughly test the isel patterns.
- fix stacked register allocation order: (for readability) we don't want
the out? registers being the first ones used
- fix up floating point
(nb http://gcc.gnu.org/wiki?pagename=ia64%20floating%20point )
- bundling!
(we will avoid the mess that is:
http://gcc.gnu.org/ml/gcc/2003-12/msg00832.html )
- instruction scheduling (hmmmm! ;)
- write truly inspirational documentation
- if-conversion (predicate database/knowledge? etc etc)
- counted loop support
- make integer + FP mul/div more clever (we have fixed pseudocode atm)
- track and use comparison complements
INFO:
- we are strictly LP64 here, no support for ILP32 on HP-UX. Linux users
don't need to worry about this.
- i have instruction scheduling/bundling pseudocode, that really works
(has been tested, albeit at the perl-script level).
so, before you go write your own, send me an email!
KNOWN DEFECTS AT THE CURRENT TIME:
- C++ vtables contain naked function pointers, not function descriptors,
which is bad. see http://llvm.cs.uiuc.edu/bugs/show_bug.cgi?id=406
- varargs are broken
- alloca doesn't work (indeed, stack frame layout is bogus)
- no support for big-endian environments
- (not really the backend, but...) the CFE has some issues on IA64.
these will probably be fixed soon.
ACKNOWLEDGEMENTS:
- Chris Lattner (x100)
- Other LLVM developers ("hey, that looks familiar")
CONTACT:
- You can email me at duraid@octopus.com.au. If you find a small bug,
just email me. If you find a big bug, please file a bug report
in bugzilla! http://llvm.cs.uiuc.edu is your one stop shop for all
things LLVM.