Triggers on AMO instructions

[Joe Rahmeh]

For the purpose of this discussion, if an address trigger has both the ld and st bit set, I am considering it to be a load-address trigger.

For AMO instructions, what happens if multiple triggers match the load/store parts of the instruction?  In particular:

1. If a load-address trigger matches an AMO instruction (timing=before) and a store-data trigger (timing=before) matches as well.  Should the store-data trigger trip? We think that we should not be loading the data in this case and consequently the store-address trigger cannot trip.

2. If a load-address trigger matches an AMO instruction (timing=before) and a store-address trigger (timing=before) matches as well.  Should the store-data trigger trip?  We would prefer a no answer.  Is that legal?

3. If a load-address trigger matches an AMO instruction (timing=before) but there is an exception with the load part of the instruction, then would a matching store-address trigger trip?  We would prefer a no answer.  Is that legal?

[Tim Newsome]

These are some serious corner cases. :-)

I agree with your interpretation, although the spec doesn't say much on this matter. (It doesn't even say what has to happen on simple load/store instructions, although it's clear what the intent is.) I'm happy to clarify the spec if you can propose some concrete changes that make this more clear.

Tim

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