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naci
0fbc2e9a52
The windows-latest preinstalled clang-cl (currently 20.1.8 at
`C:\Program Files\LLVM\bin\clang-cl.exe`) produces a lifter binary
that segfaults on calc_fib before emitting any IR, causing the rewrite
gate to fail. Clang 21.1.8 has been verified locally to compile the
lifter into a binary that lifts both calc_fib and calc_sum_array to
their expected constant returns (`ret i64 13` and `ret i64 150`).
Rolling back to clang 18.x is not an option: the runner image's MSVC STL
(14.44+) hard-requires clang 19.0.0 or newer via a static_assert in
yvals_core.h. Clang 21 satisfies that bound and dodges the clang 20.1.8
miscompile.
Upgrading via `choco upgrade llvm --version=21.1.8` keeps the existing
`C:\Program Files\LLVM\bin\clang-cl.exe` path valid, so the rest of
the pipeline (Resolve LLVM_DIR, Resolve clang-cl, Configure, Build) is
unchanged.
## Changes
- `.github/workflows/rewrite-strict-gate.yml`: add an "Upgrade clang-cl
to 21.1.8" step before `Resolve LLVM_DIR` that runs `choco upgrade
llvm` and pins `CMAKE_{C,CXX}_COMPILER` to the upgraded binary.
- `scripts/rewrite/instruction_microtests.json`: drop the `ci_skip`
entries on `calc_fib` and `calc_sum_array`.
- `docs/SCOPE.md`: bump the corpus counts to 33 samples / 177 runtime
semantic cases.
## Follow-up
Investigating the underlying clang 20.1.8 miscompile in the lifter is
still worth doing \u2014 it's almost certainly UB somewhere in the
structured-loop recovery path that clang 21 happens to tolerate. Tracked
separately.
Co-authored-by: NaC-L <nac-l@users.noreply.github.com>