> -----Original Message----- > From: Richard Henderson <richard.hender...@linaro.org> > Sent: Friday, February 7, 2020 2:53 AM > To: Taylor Simpson <tsimp...@quicinc.com>; Richard Henderson > <r...@twiddle.net>; qemu-devel@nongnu.org > Cc: Paolo Bonzini <pbonz...@redhat.com> > 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.