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From: Jordan Niethe <jniethe5@gmail.com>
Date: Mon, 23 Mar 2020 20:25:22 +1100
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Subject: Re: [PATCH v4 00/16] Initial Prefixed Instruction support
To: Nicholas Piggin <npiggin@gmail.com>
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Cc: Alistair Popple <alistair@popple.id.au>,
 Balamuruhan S <bala24@linux.ibm.com>, linuxppc-dev@lists.ozlabs.org,
 Daniel Axtens <dja@axtens.net>
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On Mon, Mar 23, 2020 at 5:22 PM Nicholas Piggin <npiggin@gmail.com> wrote:
>
> Jordan Niethe's on March 20, 2020 3:17 pm:
> > A future revision of the ISA will introduce prefixed instructions. A
> > prefixed instruction is composed of a 4-byte prefix followed by a
> > 4-byte suffix.
> >
> > All prefixes have the major opcode 1. A prefix will never be a valid
> > word instruction. A suffix may be an existing word instruction or a
> > new instruction.
> >
> > This series enables prefixed instructions and extends the instruction
> > emulation to support them. Then the places where prefixed instructions
> > might need to be emulated are updated.
> >
> > The series is based on top of:
> > https://patchwork.ozlabs.org/patch/1232619/ as this will effect
> > kprobes.
> >
> > v4 is based on feedback from Nick Piggins, Christophe Leroy and Daniel Axtens.
> > The major changes:
> >     - Move xmon breakpoints from data section to text section
> >     - Introduce a data type for instructions on powerpc
>
> Thanks for doing this, looks like a lot of work, I hope it works out :)
>
Yes it did end up touching a lot of places. I started thinking that
that maybe it would be simpler to just use a u64 instead of the struct
for  instructions.
If we always keep the word instruction / prefix in the lower bytes,
all of the current masking should still work and we can use operators
again instead of ppc_inst_equal(), etc.
It also makes printing easier. We could just #define INST_FMT %llx or
#define INST_FMT %x on powerpc32 and use that for printing out
instructions.
> Thanks,
> Nick