| commit | 7e131447da6d5f3044666a17974e15df44f0328b | [log] [tgz] |
|---|---|---|
| author | Rupert Swarbrick <rswarbrick@lowrisc.org> | Tue Jan 05 13:48:37 2021 +0000 |
| committer | Rupert Swarbrick <rswarbrick@gmail.com> | Thu Jan 07 16:00:46 2021 +0000 |
| tree | 86fef2a16be078c919f2e56d7a71ae22a4ac6869 | |
| parent | c277e3a87b350e0177f523f866aa56e2a8969784 [diff] |
[otbn] Fix ordering problems in RIG model update logic Before this patch, Model.update_for_insn updated the model "generically", based on the instruction's operands and their types and then it called any specific update function. The problem is that we don't explicitly keep "before" and "after" versions of registers (as done by the commit() methods in the ISS), so the specific updater function could get a stale version of an input argument. This doesn't matter for most operands (because, at worst, writing an indeterminate value to the operand just forgets its value), but does matter for x1, where something like addi x2, x1, 123 ended up using the element immediately below the top of the stack when calculating the new value for x2. To fix things, we make the specialized update_for_FOO instructions call the generic update logic explicitly. That way, we can do any required reads first and apply any required changes afterwards. Signed-off-by: Rupert Swarbrick <rswarbrick@lowrisc.org>
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