RE: [PATCH] Add support for a helper with 7 arguments

[Taylor Simpson]

> -----Original Message-----
> From: Richard Henderson <address@hidden>
> Sent: Friday, February 7, 2020 2:53 AM
> To: Taylor Simpson <address@hidden>; Richard Henderson
> <address@hidden>; address@hidden
> Cc: Paolo Bonzini <address@hidden>
> Subject: Re: [PATCH] Add support for a helper with 7 arguments
>
> On 2/7/20 4:46 AM, Taylor Simpson wrote:
> >> I think that we can do the store immediately -- I give specifics above.  Do
> you
> >> have a counter-example?  Admittedly I'm new to browsing the
> architecture,
> >> but I
> >> don't see a legal packet for which you can't just Store Now.
> >
> > You can have two stores in a packet, and the second one could fault.  If
> anything in the packet faults, none of the instructions commit.
>
> Then what does the manual mean when it says "dual stores have non-
> parallel
> semantics"?  Is that solely about the semantics of the bytes in memory?

Correct.  For example, this packet
    {
        memw(r5) = r6
        memb(r5) = r7
    }
Will store the word in memory with r6 and then overwrite the first byte with 
the byte from r7.