Bartosz Taudul 1dfcacd802 Collect entry stacks for "was this symbol reached" statistics. ...

SymbolStats now has two additional entry stack maps, which record the
call stacks below every occurrence of a symbol in a sample, not only
when the symbol was at the top of the stack:

- wasReached counts each occurrence separately. If a symbol re-enters
  itself through recursion, every re-entry adds an entry stack, which
  will itself contain the symbol somewhere below.
- wasReachedNonReentrant counts only the outermost occurrence, so each
  sample contributes exactly once and recursion is ignored. The sum of
  counts in this map equals the symbol's inclusive sample count.

To achieve this, the call stack is walked bottom-up, which makes the
first encountered occurrence of a symbol the outermost one. Symbols at
inline positions get the remaining inline frames of their frame group
as a synthetic frame, mirroring what was already done for the top of
the stack.

The wasExecuting and wasExecutingBase maps are now filled by the same
walk, as its topmost-frame special case. The keys they receive are
identical to what the previous code produced.

Note that there is no "base" variant of the reached maps. A base symbol
is present as the last frame of every frame group that contains its
inline functions, so its wasReached map already covers the whole symbol
at base granularity. Merging in the inline symbols' maps, as done for
wasExecutingBase, would only multi-count the same samples.

2026-07-25 17:02:42 +02:00

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