Re: [Qemu-devel] [RFC PATCH] s390x-linux-user

[Blue Swirl <blauwirbel@gmail.com>]

On 6/26/09, Paul Brook <paul@codesourcery.com> wrote:
> On Friday 26 June 2009, Blue Swirl wrote:
>  > On 6/26/09, Ulrich Hecht <uli@suse.de> wrote:
>  > >  There is a very peculiar S/390 instruction called "EXECUTE". What it
>  > > does is to take another instruction stored somewhere in memory,
>  > > logical-OR the second byte of the instruction with the LSB of R0 and then
>  > > execute the result, without changing the instruction in memory or the
>  > > program counter. Any idea how to implement this in QEMU? Currently, I'm
>  > > interpreting the couple of instructions that GCC uses EXECUTE with, but
>  > > in the long run that would amount to implementing a second emulator...
>  >
>  > Maybe something like this: Make a special TB of the EXECUTE
>  > instruction and add LSB of R0 to TB flags for these TBs. Then you can
>  > examine R0, OR and generate code at translation time. The TBs linking
>  > to EXECUTE TB may need to be special too in order to track for R0.
>
>
> That's not sufficient. The results also depend on the referenced instruction.

Then add the second byte of the referenced instruction to TB flags? Or
maybe just the result of the OR operation for compactness?