[LLVMdev] Proposed implementation of N3333 hashing interfaces for LLVM (and possible libc++)

[Jim Grosbach]

On Feb 29, 2012, at 4:24 AM, Jay Foad wrote:

> On 29 February 2012 11:47, James Molloy <james.molloy at arm.com> wrote:
>>> (But if we only care about
>>> running on x86-64, this won't be a problem.)
>> 
>> Please, no. We have a cortex-a9 native buildbot already in lab.llvm.org and
>> as manufacturers emit faster ARM chips we (ARM) will want to have LLVM run
>> native on them.
>> 
>> You've also got the OpenCL use case etc.
>> 
>> Please bear ARM in mind.
> 
> Right. (But ARMv7 uses the same ldr instruction for aligned and
> unaligned loads (doesn't it?) so it's not an issue there.)
> 

Sorta. It's the same instruction, but on some implementations, unaligned loads will cause an exception, so the compiler may need to generate LDRB sequences instead. There's also the VLD* instructions to consider. Depending on what's being loaded, there's all sorts of potential tricks that can be played. We should try to be careful and give the compiler as many hints about alignment as we can.

-Jim

> Jay.
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