[PATCH] [ARM64] Fix the misleading diagnostic on bad extend amount of reg+reg addressing mode.

[Tim Northover]

Hi Kevin,

Nevertheless, I'd prefer a vague diagnostic like "invalid offset in memory address" to putting this code in the AsmParser.

If you really want more accurate diagnostics then we need to do in some way that actually improves the code quality, not just the diagnostic quality.

Cheers.

Tim.

http://reviews.llvm.org/D3662