On July 27, 2018 3:27:49 PM GMT+02:00, Paul Koning <paulkon...@comcast.net> wrote: > > >> On Jul 27, 2018, at 5:37 AM, Richard Earnshaw ><richard.earns...@arm.com> wrote: >> >> >> This patch is intended as an example of all that is needed if the >> target system doesn't support CPUs that have speculative execution. >> I've chosen the pdp11 port on the basis that it's old enough that >this >> is likely to be true for all existing implementations and that there >> is also little chance of that changing in future! >> >> * config/pdp11/pdp11.c (TARGET_HAVE_SPECULATION_SAFE_VALUE): >Redefine >> to speculation_safe_value_not_needed. >> --- >> gcc/config/pdp11/pdp11.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> <0009-pdp11-example-of-a-port-not-needing-a-speculation-ba.patch> > >Correct, no speculative instruction now, and I don't think any of the >people constructing PDP11s (yes there are some) are going to be adding >it.
It's not really about speculative instructions but about things like having a branch predictor and ways to recover from badly predicted ones and thus from wrongly speculatively executed regular instructions. Probably every pipelined CPU implementation nowadays has speculative execution. Richard. >Thanks Richard. > > paul
