[haiku-development] Re: A modest (FatELF) proposal
- From: David Given <dg@xxxxxxxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Mon, 19 Nov 2012 23:54:09 +0000
On 19/11/12 23:17, Ingo Weinhold wrote:
[...]
> PS: What I'd really like to see is support for LLVM bytecode binaries.
> Why fat when it can be portable?
It's been done, and quite successfully:
http://en.wikipedia.org/wiki/Architecture_Neutral_Distribution_Format
http://en.wikipedia.org/wiki/TenDRA_Compiler
TenDRA and ANDF died the death, but the source is still around.
Ideally, doing LLVM bytecode binaries should be fairly easy, as the
toolchain is already there; doing the final-stage translation at install
time is a single invocation of llc.
Practically, unfortunately, it doesn't work in real life these days as
with the advent of 64-bit processors C and C++ now bake
architecture-specific information into the code as part of the
compilation process. e.g.:
int i = sizeof(void*);
int j = i * 2;
int k = (void*)(char*)j;
LLVM bitcode does have the ability to encode this sort of stuff into the
format, but the semantics don't match C. clang doesn't even bother to
try and will produce different bitcode for the above depending on what
architecture you tell it you're compiling.
And then of course as soon as you start talking about C++ and object
layouts in memory you're in a hideous world of pain, and can kiss any
kind of ABI conformance goodbye.
(If you want to see how to do this *wrong*, go look at 'natural
indexing' in the EFI bytecode spec...)
That said, you can make it work provided you're willing to limit
yourself to a lowest-common-denominator memory layout. For my day job I
do this kind of thing for a living (see http://antixlabs.com); we use
ILP32 everywhere, because we're targeting games and don't need 64-bit
addresses. Is Haiku willing to do that?
--
ââââ ïïïïïïïïïïïïïï âââââ http://www.cowlark.com âââââ
â "Of course, on a sufficiently small planet, 40 km/hr is, in fact,
â sufficient to punt the elastic spherical cow into low orbit." ---
â Brooks Moses on r.a.sf.c
Other related posts:
