Article: ARM Goes 64-bit
By: Richard Cownie (tich.delete@this.pobox.com), August 17, 2012 4:13 pm
Room: Moderated Discussions
Wilco (Wilco.Dijkstra.delete@this.ntlworld.com) on August 17, 2012 2:41 pm wrote:
> IIRC most 64-bit architectures
> zero-extend a 32-bit load. That means you can use 32-bit pointers to access the
> first 4GB without any penalty at all. There is an effort to create an x32 ABI on
> x64 that does exactly that.
Maybe, but there are two cases:
1) All your data fits in 4GB (or maybe 2GB). In that case
you should just run in 32bit mode, if your architecture has one.
2) Your data might go beyond 4GB. And in that case the pain of
managing separate regions for below-4GB and above-4GB memory,
requiring different instruction sequences to access the different
flavors of pointers, would be simply awful - probably much
more effort than using compressed pointers into a uniform
address space.
So I don't think there's much benefit to this in general - though I guess
it might be useful for the particular case of x86 vs x86_64, where the
32bit architecture has a horrible shortage of registers. But I don't
x86_64 would let you use a 32bit register as a 64bit address, does it ?
> IIRC most 64-bit architectures
> zero-extend a 32-bit load. That means you can use 32-bit pointers to access the
> first 4GB without any penalty at all. There is an effort to create an x32 ABI on
> x64 that does exactly that.
Maybe, but there are two cases:
1) All your data fits in 4GB (or maybe 2GB). In that case
you should just run in 32bit mode, if your architecture has one.
2) Your data might go beyond 4GB. And in that case the pain of
managing separate regions for below-4GB and above-4GB memory,
requiring different instruction sequences to access the different
flavors of pointers, would be simply awful - probably much
more effort than using compressed pointers into a uniform
address space.
So I don't think there's much benefit to this in general - though I guess
it might be useful for the particular case of x86 vs x86_64, where the
32bit architecture has a horrible shortage of registers. But I don't
x86_64 would let you use a 32bit register as a 64bit address, does it ?
Topic | Posted By | Date |
---|---|---|
New Article: ARM Goes 64-bit | David Kanter | 2012/08/14 12:04 AM |
New Article: ARM Goes 64-bit | none | 2012/08/14 12:44 AM |
New Article: ARM Goes 64-bit | David Kanter | 2012/08/14 01:04 AM |
MIPS MT-ASE | Paul A. Clayton | 2012/08/14 09:01 AM |
MONITOR/MWAIT | EduardoS | 2012/08/14 10:08 AM |
MWAIT not specifically MT | Paul A. Clayton | 2012/08/14 10:36 AM |
MWAIT not specifically MT | EduardoS | 2012/08/15 03:16 PM |
MONITOR/MWAIT | anonymou5 | 2012/08/14 11:07 AM |
MONITOR/MWAIT | EduardoS | 2012/08/15 03:20 PM |
MIPS MT-ASE | rwessel | 2012/08/14 10:14 AM |
New Article: ARM Goes 64-bit | SHK | 2012/08/14 02:01 AM |
New Article: ARM Goes 64-bit | anon | 2012/08/14 02:37 AM |
New Article: ARM Goes 64-bit | Richard Cownie | 2012/08/14 03:57 AM |
New Article: ARM Goes 64-bit | anon | 2012/08/14 04:29 AM |
New Article: ARM Goes 64-bit | none | 2012/08/14 04:44 AM |
New Article: ARM Goes 64-bit | anon | 2012/08/14 05:28 AM |
New Article: ARM Goes 64-bit | anon | 2012/08/14 05:32 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/08/14 06:06 AM |
New Article: ARM Goes 64-bit | none | 2012/08/14 05:40 AM |
AArch64 select better than cmov | Paul A. Clayton | 2012/08/14 06:08 AM |
New Article: ARM Goes 64-bit | anon | 2012/08/14 06:12 AM |
New Article: ARM Goes 64-bit | none | 2012/08/14 06:25 AM |
Predicated ld/store are useful | Paul A. Clayton | 2012/08/14 06:48 AM |
Predicated ld/store are useful | none | 2012/08/14 06:56 AM |
Predicated ld/store are useful | anon | 2012/08/14 07:07 AM |
Predicated stores might not be that bad | Paul A. Clayton | 2012/08/14 07:27 AM |
Predicated stores might not be that bad | David Kanter | 2012/08/15 01:14 AM |
Predicated stores might not be that bad | Michael S | 2012/08/15 11:41 AM |
Predicated stores might not be that bad | R Byron | 2012/08/17 04:09 AM |
New Article: ARM Goes 64-bit | anon | 2012/08/14 06:54 AM |
New Article: ARM Goes 64-bit | none | 2012/08/14 07:04 AM |
New Article: ARM Goes 64-bit | anon | 2012/08/14 07:43 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/08/14 06:07 AM |
New Article: ARM Goes 64-bit | anon | 2012/08/14 06:20 AM |
New Article: ARM Goes 64-bit | none | 2012/08/14 06:29 AM |
New Article: ARM Goes 64-bit | anon | 2012/08/14 07:00 AM |
New Article: ARM Goes 64-bit | Michael S | 2012/08/14 03:43 PM |
New Article: ARM Goes 64-bit | Richard Cownie | 2012/08/14 06:53 AM |
OT: Conrad's "Youth" | Richard Cownie | 2012/08/14 07:20 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/08/14 06:04 AM |
New Article: ARM Goes 64-bit | mpx | 2012/08/14 08:59 AM |
New Article: ARM Goes 64-bit | Antti-Ville Tuunainen | 2012/08/14 09:16 AM |
New Article: ARM Goes 64-bit | anonymou5 | 2012/08/14 11:03 AM |
New Article: ARM Goes 64-bit | name99 | 2012/11/17 03:31 PM |
Microarchitecting a counter register | Paul A. Clayton | 2012/11/17 07:37 PM |
New Article: ARM Goes 64-bit | bakaneko | 2012/08/14 04:21 AM |
New Article: ARM Goes 64-bit | name99 | 2012/11/17 03:40 PM |
New Article: ARM Goes 64-bit | EduardoS | 2012/11/17 04:52 PM |
New Article: ARM Goes 64-bit | Doug S | 2012/11/17 05:48 PM |
New Article: ARM Goes 64-bit | bakaneko | 2012/11/18 05:40 PM |
New Article: ARM Goes 64-bit | Wilco | 2012/11/19 07:59 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/11/19 08:23 AM |
New Article: ARM Goes 64-bit | Wilco | 2012/11/19 09:31 AM |
Downloading µarch-specific binaries? | Paul A. Clayton | 2012/11/19 11:21 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/11/19 11:41 AM |
New Article: ARM Goes 64-bit | Wilco | 2012/11/21 07:44 AM |
JIT vs. static compilation (Was: New Article: ARM Goes 64-bit) | VMguy | 2012/11/22 03:21 AM |
JIT vs. static compilation (Was: New Article: ARM Goes 64-bit) | David Kanter | 2012/11/22 12:12 PM |
JIT vs. static compilation (Was: New Article: ARM Goes 64-bit) | Gabriele Svelto | 2012/11/23 03:50 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/11/23 10:09 AM |
New Article: ARM Goes 64-bit | EBFE | 2012/11/26 01:24 AM |
New Article: ARM Goes 64-bit | Gabriele Svelto | 2012/11/26 03:33 AM |
New Article: ARM Goes 64-bit | EBFE | 2012/11/27 11:17 PM |
New Article: ARM Goes 64-bit | Gabriele Svelto | 2012/11/28 02:32 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/11/26 12:16 PM |
New Article: ARM Goes 64-bit | EBFE | 2012/11/28 12:33 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/11/28 05:53 AM |
New Article: ARM Goes 64-bit | Michael S | 2012/11/28 06:15 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/11/28 07:33 AM |
New Article: ARM Goes 64-bit | Michael S | 2012/11/28 09:16 AM |
New Article: ARM Goes 64-bit | EduardoS | 2012/11/28 09:53 AM |
New Article: ARM Goes 64-bit | Eugene Nalimov | 2012/11/28 05:58 PM |
Amazing! | EduardoS | 2012/11/28 07:25 PM |
Amazing! (non-italic response) | EduardoS | 2012/11/28 07:25 PM |
Amazing! | EBFE | 2012/11/28 08:20 PM |
Undefined behaviour doubles down | EduardoS | 2012/11/28 09:10 PM |
New Article: ARM Goes 64-bit | EBFE | 2012/11/28 07:54 PM |
New Article: ARM Goes 64-bit | EduardoS | 2012/11/28 09:21 PM |
Have you heard of Transmeta? | David Kanter | 2012/11/19 03:47 PM |
New Article: ARM Goes 64-bit | bakaneko | 2012/11/19 09:08 AM |
New Article: ARM Goes 64-bit | David Kanter | 2012/11/19 03:40 PM |
Semantic Dictionary Encoding | Ray | 2012/11/19 10:37 PM |
New Article: ARM Goes 64-bit | Rohit | 2012/11/20 04:48 PM |
New Article: ARM Goes 64-bit | David Kanter | 2012/11/20 11:07 PM |
New Article: ARM Goes 64-bit | Wilco | 2012/11/21 06:41 AM |
New Article: ARM Goes 64-bit | David Kanter | 2012/11/21 10:12 AM |
A JIT example | Mark Roulo | 2012/11/21 10:30 AM |
A JIT example | Wilco | 2012/11/21 07:04 PM |
A JIT example | rwessel | 2012/11/21 09:05 PM |
A JIT example | Gabriele Svelto | 2012/11/23 03:53 AM |
A JIT example | EduardoS | 2012/11/23 10:13 AM |
A JIT example | Wilco | 2012/11/23 01:41 PM |
A JIT example | EduardoS | 2012/11/23 02:06 PM |
A JIT example | Gabriele Svelto | 2012/11/23 04:09 PM |
A JIT example | Symmetry | 2012/11/26 05:58 AM |
New Article: ARM Goes 64-bit | Ray | 2012/11/19 10:27 PM |
New Article: ARM Goes 64-bit | David Kanter | 2012/08/14 09:11 AM |
v7-M is Thumb-only | Paul A. Clayton | 2012/08/14 06:58 AM |
Minor suggested correction | Paul A. Clayton | 2012/08/14 08:33 AM |
Minor suggested correction | anon | 2012/08/14 08:57 AM |
New Article: ARM Goes 64-bit | Exophase | 2012/08/14 08:33 AM |
New Article: ARM Goes 64-bit | David Kanter | 2012/08/14 09:16 AM |
New Article: ARM Goes 64-bit | jigal | 2012/08/15 01:49 PM |
Correction re ARM and BBC Micro | Paul | 2012/08/14 08:59 PM |
Correction re ARM and BBC Micro | Per Hesselgren | 2012/08/15 03:27 AM |
Memory BW so low | Per Hesselgren | 2012/08/15 03:14 AM |
Memory BW so low | none | 2012/08/15 11:16 AM |
New Article: ARM Goes 64-bit | dado | 2012/08/15 10:25 AM |
Number of GPRs | Kenneth Jonsson | 2012/08/16 02:35 PM |
Number of GPRs | Exophase | 2012/08/16 02:52 PM |
Number of GPRs | Kenneth Jonsson | 2012/08/17 02:41 AM |
Ooops, missing link... | Kenneth Jonsson | 2012/08/17 02:44 AM |
64-bit pointers eat some performance | Paul A. Clayton | 2012/08/17 06:19 AM |
64-bit pointers eat some performance | bakaneko | 2012/08/17 08:37 AM |
Brute force seems to work | Paul A. Clayton | 2012/08/17 10:08 AM |
Brute force seems to work | bakaneko | 2012/08/17 11:15 AM |
64-bit pointers eat some performance | Richard Cownie | 2012/08/17 08:46 AM |
Pointer compression is atypical | Paul A. Clayton | 2012/08/17 10:43 AM |
Pointer compression is atypical | Richard Cownie | 2012/08/17 12:57 PM |
Pointer compression is atypical | Howard Chu | 2012/08/22 10:17 PM |
Pointer compression is atypical | Richard Cownie | 2012/08/23 04:48 AM |
Pointer compression is atypical | Howard Chu | 2012/08/23 06:51 AM |
Pointer compression is atypical | Wilco | 2012/08/17 02:41 PM |
Pointer compression is atypical | Richard Cownie | 2012/08/17 04:13 PM |
Pointer compression is atypical | Ricardo B | 2012/08/19 10:44 AM |
Pointer compression is atypical | Howard Chu | 2012/08/22 10:08 PM |
Unified libraries? | Paul A. Clayton | 2012/08/23 07:49 AM |
Pointer compression is atypical | Richard Cownie | 2012/08/23 08:44 AM |
Pointer compression is atypical | Howard Chu | 2012/08/23 05:17 PM |
Pointer compression is atypical | anon | 2012/08/23 08:15 PM |
Pointer compression is atypical | Howard Chu | 2012/08/23 09:33 PM |
64-bit pointers eat some performance | Foo_ | 2012/08/18 12:09 PM |
64-bit pointers eat some performance | Richard Cownie | 2012/08/18 05:25 PM |
64-bit pointers eat some performance | Richard Cownie | 2012/08/18 05:32 PM |
Page-related benefit of small pointers | Paul A. Clayton | 2012/08/23 08:36 AM |
Number of GPRs | Wilco | 2012/08/17 06:31 AM |
Number of GPRs | Kenneth Jonsson | 2012/08/17 11:54 AM |
Number of GPRs | Exophase | 2012/08/17 12:44 PM |
Number of GPRs | Kenneth Jonsson | 2012/08/17 01:22 PM |
Number of GPRs | Wilco | 2012/08/17 02:53 PM |
What about dynamic utilization? | Exophase | 2012/08/17 09:30 AM |
Compiler vs. assembly aliasing knowledge? | Paul A. Clayton | 2012/08/17 10:20 AM |
Compiler vs. assembly aliasing knowledge? | Exophase | 2012/08/17 11:09 AM |
Compiler vs. assembly aliasing knowledge? | anon | 2012/08/18 02:23 AM |
Compiler vs. assembly aliasing knowledge? | Ricardo B | 2012/08/19 11:02 AM |
Compiler vs. assembly aliasing knowledge? | anon | 2012/08/19 06:07 PM |
Compiler vs. assembly aliasing knowledge? | Ricardo B | 2012/08/19 07:26 PM |
Compiler vs. assembly aliasing knowledge? | anon | 2012/08/19 10:03 PM |
Compiler vs. assembly aliasing knowledge? | anon | 2012/08/20 01:59 AM |
Number of GPRs | David Kanter | 2012/08/17 12:46 PM |
RAT issues as part of reason 1 | Paul A. Clayton | 2012/08/17 02:18 PM |
Number of GPRs | name99 | 2012/11/17 06:37 PM |
Large ARFs increase renaming cost | Paul A. Clayton | 2012/11/17 09:23 PM |
Number of GPRs | David Kanter | 2012/08/16 03:31 PM |
Number of GPRs | Richard Cownie | 2012/08/16 05:17 PM |
32 GPRs ~2-3% | Paul A. Clayton | 2012/08/16 06:27 PM |
Oops, Message-ID: aaed6e38-c7bd-467e-ba41-f40cf1020e5e@googlegroups.com (NT) | Paul A. Clayton | 2012/08/16 06:29 PM |
32 GPRs ~2-3% | Exophase | 2012/08/16 10:06 PM |
R31 as SP/zero is kind of neat (NT) | Paul A. Clayton | 2012/08/17 06:23 AM |
32 GPRs ~2-3% | rwessel | 2012/08/17 08:24 AM |
32 GPRs ~2-3% | Exophase | 2012/08/17 09:16 AM |
32 GPRs ~2-3% | Max | 2012/08/17 04:19 PM |
32 GPRs ~2-3% | name99 | 2012/11/17 07:43 PM |
Number of GPRs | mpx | 2012/08/17 01:11 AM |
Latency and power | Paul A. Clayton | 2012/08/17 06:54 AM |
Number of GPRs | bakaneko | 2012/08/17 03:09 AM |
New Article: ARM Goes 64-bit | Steve | 2012/08/17 02:12 PM |
New Article: ARM Goes 64-bit | David Kanter | 2012/08/19 12:42 PM |
New Article: ARM Goes 64-bit | Doug S | 2012/08/19 02:02 PM |
New Article: ARM Goes 64-bit | Anon | 2012/08/19 07:16 PM |
New Article: ARM Goes 64-bit | Steve | 2012/08/30 07:51 AM |
Scalar vs Vector registers | Robert David Graham | 2012/08/19 05:19 PM |
Scalar vs Vector registers | David Kanter | 2012/08/19 05:29 PM |
New Article: ARM Goes 64-bit | Baserock ARM servers | 2012/08/21 04:13 PM |
Baserock ARM servers | Sysanon | 2012/08/21 04:14 PM |
A-15 virtualization and LPAE? | Paul A. Clayton | 2012/08/21 06:13 PM |
A-15 virtualization and LPAE? | Anon | 2012/08/21 07:13 PM |
Half-depth advantages? | Paul A. Clayton | 2012/08/21 08:42 PM |
Half-depth advantages? | Anon | 2012/08/22 03:33 PM |
Thanks for the information (NT) | Paul A. Clayton | 2012/08/22 04:04 PM |
A-15 virtualization and LPAE? | C. Ladisch | 2012/08/23 11:12 AM |
A-15 virtualization and LPAE? | Paul | 2012/08/23 03:17 PM |
Excessive pessimism | Paul A. Clayton | 2012/08/23 04:08 PM |
Excessive pessimism | David Kanter | 2012/08/23 05:05 PM |
New Article: ARM Goes 64-bit | Michael S | 2012/08/22 07:12 AM |
BTW, Baserock==product, Codethink==company (NT) | Paul A. Clayton | 2012/08/22 08:56 AM |
New Article: ARM Goes 64-bit | Reinoud Zandijk | 2012/08/21 11:27 PM |