Profiling showed that maintaining this ssa_srcs set consumes ~3% of CTS time
with a debugoptimized build. Unfortunately, we really do benefit from getting
this coverage in CI. So rather than remove the validation, let's optimize the
data structure used so we can keep the coverage at a fraction of the cost.
The expensive piece is the pointer set, which is backed by a relatively
expensive hash table. It would be much cheaper to use an invasive set instead,
with a single "present" bit. We don't want to bloat nir_src for this, however
there's an easy solution: use a tagged pointer to steal a bit in the nir_src for
the job. We untag everything at the end of validation (and this meta-invariant
is asserted with an auxiliary counter), so while we mutate the IR while
validating, the mutations do not escape nir_validate.
We tag the parent pointer and not the def pointer, because it is dramatically
less used and therefore has far fewer disrupted call sites.
The M1 job is improved from 3:03 to 2:55 of deqp-runner reported time, which is
excellent.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26084>
Alyssa Rosenzweig
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