Supporting 64-bit ARM systems [LWN.net]

Supporting 64-bit ARM systems

Posted Jul 11, 2012 3:55 UTC (Wed) by ringerc (subscriber, #3071)
In reply to: Supporting 64-bit ARM systems by jzbiciak
Parent article: Supporting 64-bit ARM systems

Thanks for that. I didn't realise that ARM arches retained such a high level of source compatibility despite continually breaking binary compatibility.

I've only dealt with ARM in a few areas like mutex/locking asm helpers, where the best sequence to use is different for different sub-architectures.

I can see that the break of source compatibility would make v8/ARM64 a bigger challenge if perfect source-level ASM compatibility has been the norm up until now. It still sounds more like an ia32-to-x86_64 move than an ia32-to-itanic move, though.

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Supporting 64-bit ARM systems

Posted Jul 11, 2012 7:09 UTC (Wed) by cmarinas (subscriber, #39468) [Link]

The assembler syntax is different. It has some similarities for a few mnemonics but you cannot compile one into the other (like we could do with the Thumb-2 unified syntax). The register names are different: R0 on 32-bit vs X0 on 64-bit. Even the comment syntax has been changed from "@" to "//" (because of some clashes of the former).