pc: add compare for the first instr pc of a commit group.

[NewPaulWalker]

Sometimes the dut or ref will wrongly jump to a pc, and if their reg state still match in the next instructions, this will make debugging very difficult. So I add the comparison to the pc.

[klin02]

When define CONFIG_DIFFTEST_SQUASH, multi commits in a group will be squashed to a single one, which means next squashed commit[0].pc will mismatch previous REF pc.

Please add ifndef CONFIG_DIFFTEST_SQUASH when using pc_mismatch.

[poemonsense]

First pc of REF is copied from the DUT.

[NewPaulWalker]

First pc of REF is copied from the DUT.

Yes, when initializing difftest, the REF state is copied from the DUT. What this pr wants to do is to compare whether the first pc in every commit group matches.

[poemonsense]

First pc of REF is copied from the DUT.

Yes, when initializing difftest, the REF state is copied from the DUT. What this pr wants to do is to compare whether the first pc in every commit group matches.

I see. So the problem is that difftest is missing the comparison of pc. Right?

I remember there was the comparison. Maybe it is removed at some point.

[NewPaulWalker]

I see. So the problem is that difftest is missing the comparison of pc. Right?

Yes.