[Bug binutils/23230] aarch64: objdump disassembles invalid mrs

[egeyar.bagcioglu at oracle dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=23230

--- Comment #3 from Egeyar Bagcioglu <egeyar.bagcioglu at oracle dot com> ---
I prepared a patch according to "ARM Architecture Reference Manual, ARMv8, for
ARMv8-A architecture profile". However, the patch triggered a failure in a
test-case. Then, I realized that what my patch does was reverting the following
patch:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=df7b4545b2b49572ab63690c130df973af109615
It seems that the definitions of mrs and msr were relaxed on purpose.

I have also checked his old e-mail about it:
https://sourceware.org/ml/binutils/2014-09/msg00022.html
I see what it does. It enables one to define instructions such as sys, sysl,
hint and clrex in terms of mrs and msr. However, it is not mentioned in the
manual. Moreover, as pointed out by this bug, that patch lets a big range of
undefined instructions to fall into msr/mrs definition. Because, the above 4
instructions each have many more defined bits than mrs/msr do. My instinct to
follow the manual would prefer the previous stricter version of mrs/msr.

I am not able to add Jiong, the patch owner, to the CC list of this bug. I'm
notifying him via e-mail to get his opinion on this matter. I hope he can tell
us why the above patch was necessary so that a better informed decision can be
made on the matter.

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