If we have a refutation Z3 query timed out (UNDEF), allow a couple of
retries to improve stability of the query. By default allow 2 retries,
which will give us in maximum of 3 solve attempts per query.
Retries should help mitigating flaky Z3 queries.
See the details in the following RFC:
https://discourse.llvm.org/t/analyzer-rfc-retry-z3-crosscheck-queries-on-timeout/83711
Note that with each attempt, we spend more time per query.
Currently, we have a 15 seconds timeout per query - which are also in
effect for the retry attempts.
---
Why should this help?
In short, retrying queries should bring stability because if a query
runs long
it's more likely that it did so due to some runtime anomaly than it's on
the edge of succeeding. This is because most queries run quick, and the
queries that run long, usually run long by a fair amount.
Consequently, retries should improve the stability of the outcome of the
Z3 query.
In general, the retries shouldn't increase the overall analysis time
because it's really rare we hit the 0.1% of the cases when we would do
retries. But keep in mind that the retry attempts can add up if many
retries are allowed, or the individual query timeout is large.
CPP-5920
This is exactly as originally landed in #95129,
but now the minimal Z3 version was increased to meet this change in #96682.
https://discourse.llvm.org/t/bump-minimal-z3-requirements-from-4-7-1-to-4-8-9/79664/4
---
This patch is a functional change.
https://discourse.llvm.org/t/analyzer-rfc-taming-z3-query-times/79520
As a result of this patch, individual Z3 queries in refutation will be
bound by 300ms. Every report equivalence class will be processed in at
most 1 second.
The heuristic should have only really marginal observable impact -
except for the cases when we had big report eqclasses with long-running
(15s) Z3 queries, where previously CSA effectively halted. After this
patch, CSA will tackle such extreme cases as well.
(cherry picked from commit eacc3b3504be061f7334410dd0eb599688ba103a)
This patch is a functional change.
https://discourse.llvm.org/t/analyzer-rfc-taming-z3-query-times/79520
As a result of this patch, individual Z3 queries in refutation will be
bound by 300ms. Every report equivalence class will be processed in
at most 1 second.
The heuristic should have only really marginal observable impact -
except for the cases when we had big report eqclasses with long-running
(15s) Z3 queries, where previously CSA effectively halted.
After this patch, CSA will tackle such extreme cases as well.
Reviewers: NagyDonat, haoNoQ, Xazax-hun, Szelethus, mikhailramalho
Reviewed By: NagyDonat
Pull Request: https://github.com/llvm/llvm-project/pull/95129
