[ctxprof] Auto root detection: trie for stack samples

[mtrofin]

An initial patch for supporting automated root detection. The auto-detector is introduced subsequently, but this patch introduces a datastructure for capturing sampled stacks, per thread, in a trie, and inferring from such samples which functions are reasonable roots.

[mtrofin]

• [ctxprof] root autodetection mechanism #133147
• [ctxprof][nfc] Move 2 implementation functions up in CtxInstrProfiling.cpp #133146
• [ctxprof] Auto root detection: trie for stack samples #133106 👈 (View in Graphite)
• main

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[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[kazutakahirata]

LGTM modulo a couple of nits.

[snehasish]

lgtm

[mtrofin]

Merge activity

• Mar 28, 11:06 PM EDT: A user started a stack merge that includes this pull request via Graphite.
• Mar 28, 11:08 PM EDT: A user merged this pull request with Graphite.

[llvm-ci]

LLVM Buildbot has detected a new failure on builder clang-aarch64-sve2-vla running on linaro-g4-01 while building compiler-rt at step 7 "ninja check 1".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/198/builds/3248

Here is the relevant piece of the build log for the reference

Step 7 (ninja check 1) failure: stage 1 checked (failure)
...
PASS: Flang :: Driver/print-effective-triple.f90 (24736 of 96422)
PASS: Flang :: Driver/linker-flags.f90 (24737 of 96422)
PASS: Flang :: Driver/phases.f90 (24738 of 96422)
PASS: Flang :: Driver/print-resource-dir.F90 (24739 of 96422)
PASS: Flang :: Driver/parse-fir-error.ll (24740 of 96422)
PASS: Flang :: Driver/predefined-macros-compiler-version.F90 (24741 of 96422)
PASS: Flang :: Driver/override-triple.ll (24742 of 96422)
PASS: Flang :: Driver/mlir-pass-pipeline.f90 (24743 of 96422)
PASS: Flang :: Driver/mlink-builtin-bc.f90 (24744 of 96422)
UNRESOLVED: Flang :: Driver/slp-vectorize.ll (24745 of 96422)
******************** TEST 'Flang :: Driver/slp-vectorize.ll' FAILED ********************
Test has no 'RUN:' line
********************
PASS: Flang :: Driver/parse-error.ll (24746 of 96422)
PASS: Flang :: Driver/fixed-line-length.f90 (24747 of 96422)
PASS: Flang :: Driver/print-pipeline-passes.f90 (24748 of 96422)
PASS: Flang :: Driver/lto-bc.f90 (24749 of 96422)
PASS: Flang :: Driver/pthread.f90 (24750 of 96422)
PASS: Flang :: Driver/missing-arg.f90 (24751 of 96422)
PASS: Flang :: Driver/scanning-error.f95 (24752 of 96422)
PASS: Flang :: Driver/print-target-triple.f90 (24753 of 96422)
PASS: Flang :: Driver/supported-suffices/f03-suffix.f03 (24754 of 96422)
PASS: Flang :: Driver/pass-plugin-not-found.f90 (24755 of 96422)
PASS: Flang :: Driver/std2018-wrong.f90 (24756 of 96422)
PASS: Flang :: Driver/pp-fixed-form.f90 (24757 of 96422)
PASS: Flang :: Driver/tco-code-gen-llvm.fir (24758 of 96422)
PASS: Flang :: Driver/supported-suffices/f08-suffix.f08 (24759 of 96422)
PASS: Flang :: Driver/parse-ir-error.f95 (24760 of 96422)
PASS: Flang :: Driver/target-gpu-features.f90 (24761 of 96422)
PASS: Flang :: Driver/target.f90 (24762 of 96422)
PASS: Flang :: Driver/q-unused-arguments.f90 (24763 of 96422)
PASS: Flang :: Driver/multiple-input-files.f90 (24764 of 96422)
PASS: Flang :: Driver/lto-flags.f90 (24765 of 96422)
PASS: Flang :: Driver/mllvm.f90 (24766 of 96422)
PASS: Flang :: Driver/unparse-with-modules.f90 (24767 of 96422)
PASS: Flang :: Driver/unsupported-vscale-max-min.f90 (24768 of 96422)
PASS: Flang :: Driver/fsave-optimization-record.f90 (24769 of 96422)
PASS: Flang :: Driver/no-duplicate-main.f90 (24770 of 96422)
PASS: Flang :: Driver/optimization-remark-invalid.f90 (24771 of 96422)
PASS: Flang :: Driver/input-from-stdin/input-from-stdin.f90 (24772 of 96422)
PASS: Flang :: Driver/falias-analysis.f90 (24773 of 96422)
PASS: Flang :: Driver/std2018.f90 (24774 of 96422)
PASS: Flang :: Driver/unparse-use-analyzed.f95 (24775 of 96422)
PASS: Flang :: Driver/target-machine-error.f90 (24776 of 96422)
PASS: Flang :: Driver/prescanner-diag.f90 (24777 of 96422)
PASS: Flang :: Driver/save-temps.f90 (24778 of 96422)
PASS: Flang :: Driver/optimization-remark-backend.f90 (24779 of 96422)
PASS: Flang :: Driver/response-file.f90 (24780 of 96422)
PASS: Flang :: Driver/fveclib.f90 (24781 of 96422)