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

[Matt Fischer]

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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