[LLVMdev] Big endian ARM?

[Chris Lattner]

On Jun 2, 2012, at 8:35 PM, Richard Pennington wrote:
>> i.e. the test of the value is optimized to use a byte load, but the ldrb is
>> done assuming a little endian address space.
>> 
>> I've been snooping around, but can't seem to find where the conversion to a
>> byte operation is done. Could someone point me in the right direction?
>> 
> 
> I've figured out my problem. I didn't adjust the data layout description string 
> in ARMTargetMachine.cpp for big endian targets.
> 
> This brings up another question. clang has its own set of description strings 
> for varying ABIs, etc. Should those strings somehow override in the code 
> generators?

The current design is that the frontend (if it attaches a TD string) is *required* to match the code generator:
http://llvm.org/docs/LangRef.html#datalayout

It is intended to allow the mid-level optimizers to know about data layout without having the code generator linked in (e.g. "opt").

-Chris