X32 ABI
x32 ABI (x32 application binary interface) is an application binary interface project for Linux that allows programs to take advantage of the benefits of x86-64 (larger number of CPU registers, better floating-point performance, faster position-independent code shared libraries, function parameters passed via registers, faster Syscall instruction... ) while using 32-bit pointers and thus avoiding the overhead of 64-bit pointers.[1][2][3]
Details
Though the x32 ABI limits the program to a virtual address space of 4 GB it also decreases the memory footprint of the program and in some cases can allow it to run faster.[1][2][3] The best results during testing were with the 181.mcf SPEC CPU 2000 benchmark in which the x32 ABI version was 40% faster than the x86-64 version.[3][4] On average x32 is 5–8% faster on the SPEC CPU integer benchmarks compared to x86-64. There is no speed advantage over x86-64 in the SPEC CPU floating point benchmarks.[5]
Feature | i386 | x32 | x86-64 |
---|---|---|---|
Max. memory per process | 4 GiB | 128 TiB | |
Integer registers | 6 (PIC) | 16 | |
FP registers | 8 | 16 | |
Pointers | 4 bytes | 8 bytes | |
64-bit arithmetic | No | Yes | |
Floating point | x87 | SSE | |
Calling convention | Memory | Registers | |
PIC prologue | 2-3 insn | None |
History
Several people had discussed the benefits of an x86-64 ABI with 32-bit pointers in the years since the Athlon 64's release in 2003, notably Donald Knuth in 2008.[6] There was little publicly visible progress towards implementing such a mode until August 27, 2011, when Hans Peter Anvin announced to the Linux kernel mailing list that he and H.J. Lu had been working on x32-ABI.[7]
That same day Linus Torvalds replied with a concern that the use of 32-bit time values in the x32 ABI could cause problems in the future.[8][9] This is because the use of 32-bit time values would cause the time values to overflow in the year 2038.[8][9] Following this request the developers of the x32 ABI changed the time values to 64-bit.[10]
A presentation at the Linux Plumbers Conference on September 7, 2011, covered the x32 ABI.[2]
The x32 ABI was merged into the Linux kernel for the 3.4 release with support being added to the GNU C Library in version 2.16.
References
- ↑ 1.0 1.1 Thorsten Leemhuis (2011-09-13). "Kernel Log: x32 ABI gets around 64-bit drawbacks". www.h-online.com. Archived from the original on 28 October 2011. Retrieved 2011-11-01.
- ↑ 2.0 2.1 2.2 "x32 - a native 32-bit ABI for x86-64". linuxplumbersconf.org. Retrieved 2012-06-12.
- ↑ 3.0 3.1 3.2 "x32-abi". Google Sites. Retrieved 2011-11-01.
- ↑ "181.mcf SPEC CPU2000 Benchmark Description File". Standard Performance Evaluation Corporation. 1999-10-14. Retrieved 2011-11-01.
- ↑ H.J. Lu, H Peter Anvin, Milind Girkar (September 2011). "X32 - A Native 32bit ABI For X86-64".
- ↑ Donald Knuth (February 2008). "Recent News: A Flame About 64-bit Pointers". Retrieved 15 May 2012.
- ↑ H. Peter Anvin (27 August 2011). "RFD: x32 ABI system call numbers". Retrieved 15 May 2012.
- ↑ 8.0 8.1 Jonathan Corbet (2011-08-29). "The x32 system call ABI". LWN.net. Retrieved 2011-11-01.
- ↑ 9.0 9.1 Linus Torvalds (2011-08-26). "Re: RFD: x32 ABI system call numbers". LWN.net. Retrieved 2011-11-01.
- ↑ H.J. Lu (2011-11-24). "X32 project status update".
External links
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