[LLVMdev] [PATCH] Apply Thumb2 ROR optimization only when Thumb2 is supported

[Bob Wilson]

I went ahead and committed it, along with a basic test case, in svn r159538.

On Jul 2, 2012, at 9:34 AM, Jim Grosbach <grosbach at apple.com> wrote:

> Hi Matt,
> 
> You're absolutely right, that pattern should definitely have an "only-in-Thumb2" predicate attached.
> 
> Do you have commit access? Also, if you have a reduced test case, that would be awesome, but the patch is correct as-is even if not.
> 
> -Jim
> 
> On Jul 2, 2012, at 8:05 AM, Matt Fischer <mattfischer84 at gmail.com> wrote:
> 
>> I've been playing around with using LLVM on one of our projects, which
>> runs on an arm1176jzf-s processor.  When compiling for Thumb, a couple
>> of the generated assembly files end up with a 'ror.w' instruction,
>> which is a Thumb2 instruction.  Since arm1176jzf-s doesn't support
>> Thumb2, the assembler then turns around and barfs on it.
>> 
>> I don't have any experience with this codebase, but after looking
>> around for a while, I think I found the culprit--there was a change
>> back in #130502 which added a peephole optimization to generate that
>> instruction, but the pattern was not made conditional on being in
>> Thumb2 mode.  If that's correct, then I believe the attached patch
>> will fix it (at the very least, it made my specific error go away).
>> Is this the right fix?
>> 
>> Thanks,
>> Matt
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