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Dividing the Linux desktop
LWN.net Weekly Edition for June 13, 2013
A report from pgCon 2013
Little things that matter in language design
Pettenò: Debunking x32 myths
Posted Jun 27, 2012 23:50 UTC (Wed) by dlang (✭ supporter ✭, #313)
In the past, some distros had kernels for i386, i486, i586, and i686. it was a major headache and not very effective. In many ways doing an entire new ABI is easier to deal with than dealing with a slight variation to an existing one.
Posted Jun 27, 2012 23:59 UTC (Wed) by nix (subscriber, #2304)
(But with regard to the flag which *does*, everything you say is true. glibc's hwcaps mechanism will allow you to implement 'slight variation on instruction set', allowing some but not all libraries to have alternate versions for various hwcaps, plus 'tls' as a now-obsolete special case. On x86, this tends to get used to compile different x86-32 binaries for machines supporting versus not supporting the CMOV instruction; on e.g. SPARC64, it is (or was) used to provide alternate versions of libraries for the SPARCv9 32-bit instruction set, which is much like x32 except ABI-compatible with the usual SPARC 32-bit ABI -- all the SPARCv9 registers plus integer multiply and divide instructions, imagine that! You can't use the hwcaps mechanism to support different ABIs though, because nothing stops a hwcapped library calling a non-hwcapped one, or vice versa.)
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