Re: making the most of a symbolic breakpoint
Re: making the most of a symbolic breakpoint
- Subject: Re: making the most of a symbolic breakpoint
- From: Greg Parker <email@hidden>
- Date: Wed, 09 Jan 2013 12:33:24 -0800
On Jan 9, 2013, at 12:01 PM, Kyle Sluder <email@hidden> wrote:
> On Wed, Jan 9, 2013, at 11:04 AM, John McCall wrote:
>> There is no one standard calling convention on ARM; ARM has revised its
>> suggested ABI multiple times. iOS follows a relatively old convention
>> which, among other things, does not pass floating-point arguments in
>> floating-point registers. This is suboptimal but not fixable without a
>> total ABI break.
>
> That's what I was afraid of. :( Did Apple take advantage of the move to
> ARMv7 to introduce a more performant calling convention?
No. On iOS, ARMv7 and ARMv6 code can interoperate freely, so there was no opportunity to introduce changes to parameter-passing.
Without heroic measures, a true ABI break means either "your old apps don't work" or "there are two copies of the OS shared library stack in memory". The sub-optimal parts of our ARM ABI aren't bad enough to justify that cost.
--
Greg Parker email@hidden Runtime Wrangler
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