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Thread: Linux x32 Support Brewing For Clang/Compiler-RT

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  1. #1
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    Default Linux x32 Support Brewing For Clang/Compiler-RT

    Phoronix: Linux x32 Support Brewing For Clang/Compiler-RT

    Improvements for LLVM's support of the Linux x32 ABI is set to improve with some work-in-progress patches for the Clang C/C++ compiler front-end and Compiler-RT runtime library...

    http://www.phoronix.com/vr.php?view=MTQ0MjE

  2. #2
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    Are there still x86-like 32-bit only processor sold in 2013 by a mainstream brand ? (AMD / Intel..).

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    Quote Originally Posted by doom_Oo7 View Post
    Are there still x86-like 32-bit only processor sold in 2013 by a mainstream brand ? (AMD / Intel..).

    I'm not sure but what does that have to do with a story about x32? (x32 requires a 64-bit CPU you know... all it does is shorten the pointer length and reduce the memory space to 32 bits to conserve memory while still allowing 64-bit math, using new instructions that aren't in 32-bit x86, using the new addressing modes in x86-64, and using all of the general purpose registers on a 64-bit x86 CPU).

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    Quote Originally Posted by chuckula View Post
    I'm not sure but what does that have to do with a story about x32? (x32 requires a 64-bit CPU you know... all it does is shorten the pointer length and reduce the memory space to 32 bits to conserve memory while still allowing 64-bit math, using new instructions that aren't in 32-bit x86, using the new addressing modes in x86-64, and using all of the general purpose registers on a 64-bit x86 CPU).
    Eek, didn't know this, sorry ! Generally I used to say x32 for 32-bit only processor like pre-amd64 era. Didn't know it was a Linux project.

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    Quote Originally Posted by doom_Oo7 View Post
    Eek, didn't know this, sorry ! Generally I used to say x32 for 32-bit only processor like pre-amd64 era. Didn't know it was a Linux project.
    Yeah just for clarification, Doom...

    32bit = x86
    32bit with 64 bit extensions = x86_64
    64bit but with 32bit register and memory lengths = x32

    Frankly I don't really see x32 really taking off... 64bit is already really engrained in people's minds and with the way RAM keeps jumping up I don't see the benefits of maintaining 3 separate architectures, despite normal 64bit being a little more expensive.

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    Quote Originally Posted by Ericg View Post
    Yeah just for clarification, Doom...

    32bit = x86
    32bit with 64 bit extensions = x86_64

    64bit but with 32bit register and memory lengths = x32
    This isn't quite right, x86_64 is real 64-bit, x32 is 32-bit with 64-bit extensions. Full 64-bit registers are available, but the default types of (I)nt, (L)ong, and (P)ointers are 32-bit, that's why it's also known as ILP32. Longer types, such as long long or explicit 64-bit types are natively supported.

    Frankly I don't really see x32 really taking off... 64bit is already really engrained in people's minds and with the way RAM keeps jumping up I don't see the benefits of maintaining 3 separate architectures, despite normal 64bit being a little more expensive.
    Obviously I see things a little differently!

    x32 won't take off unless there's the possibility to run a full distribution. The few early users (who have demonstrated significant performance advantages) including CERN, do not represent sufficient critical mass to ensure support from many upstream projects.

    There are definitely use cases where 64-bit is a big win, but that isn't so much dependent on the amount of installed RAM as the type of application, and even discarding the 5-40% potential performance advantage you need a lot more than 4GiB RAM to lose any advantage from the reduced memory consumption, especially given each process gets its own 4GiB address space.

    One more thing, on x86-64 Gentoo you can now install with a default system ABI: x86-64, x86, or x32. When you want a specific application to use a different ABI you just need to use an abi_x86_* use-flag and the dependencies required are pulled in. Other distributions also allow you to install dependencies for specific ABIs as required, although of course, not dynamically, package by package.
    Last edited by s_j_newbury; 08-22-2013 at 05:11 PM.

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