[llvm] r194253 - [ARM] In ARMAsmParser, MatchCoprocessorOperandName() permitted p10 and p11 as operands for coprocessor instructions, resulting in encodings that clash with FP/NEON instruction encodings

[Joerg Sonnenberger]

On Mon, Dec 02, 2013 at 03:41:58PM +0000, James Molloy wrote:
> Hi Joerg,
> 
> > It breaks compatibility with existing code.
> 
> But if the existing code you're referring to is incorrect, I don't see the
> issue. Incorrect code is incorrect code, and we don't keep compiler bugs
> around to satisfy legacy programs. Personally I don't see this as different
> to any other compiler bug.
> 
> >  I still haven't heard an argument for why it is needed.
> 
> The toolchain is not in compliance with the reference manuals for post-v6
> targets, AIUI.

The code in question is certainly older than the post-v6 manuals.
This feels a lot like breaking compat for no real gain. The code
certainly hasn't become simpler due to this. It does create a
non-significant amount of pain.

Joerg