llvm, llvm20: strip LLVM-bitcode sections from libLLVM*.a archives

[PawelWMS]

Summary

The llvm-static and llvm20-static sub-packages ship every libLLVM*.a archive built with clang's Thin-LTO + FatLTO objects. Each .o member therefore carries large embedded bitcode sections (.llvmbc, .llvmcmd, .llvm.lto, and defensively .gnu.lto_* / .gnu.debuglto_* in case any member happens to have been compiled with gcc -flto) on top of native code. Those sections are only useful for re-linking with LTO; the native linker ignores them when a consumer links a static archive into a regular (non-LTO) build. They typically 2–3× the compressed RPM-payload size of llvm-static and llvm20-static, which makes the resulting RPMs exceed the decompression budget of the automated package-signing pipeline (timeouts observed for all three failing archives: llvm-static-*.aarch64.rpm, llvm20-static-*.aarch64.rpm, llvm20-static-*.x86_64.rpm).

Mechanism

Adds a spec-append-lines overlay to each of base/comps/llvm/llvm.comp.toml and base/comps/llvm20/llvm20.comp.toml that injects a small loop at the end of %install:

for _archive in %{buildroot}%{_libdir}/libLLVM*.a \
                %{buildroot}%{install_libdir}/libLLVM*.a; do
    [ -f "$_archive" ] || continue
    %{__objcopy} \
        --remove-section=.llvmbc \
        --remove-section=.llvmcmd \
        --remove-section=.llvm.lto \
        --remove-section='.gnu.lto_*' \
        --remove-section='.gnu.debuglto_*' \
        "$_archive" 2>/dev/null || :
done

Path-glob rationale: the default (non-compat) build runs move_and_replace_with_symlinks %{buildroot}%{install_libdir} %{buildroot}%{_libdir} in %install, after which the real libLLVM*.a files live under %{buildroot}%{_libdir}/ and %{install_libdir} paths are symlinks back to them. The compat build keeps the archives under %{install_libdir}. The loop globs both paths and skips any non-regular file (i.e. dangling symlinks) so the overlay is layout-agnostic.

objcopy from binutils iterates over ar archive members automatically; one invocation per archive is enough. Wildcard section patterns (--remove-section='.gnu.lto_*') are supported. Missing sections are no-ops, so over-specifying the bitcode/LTO section list is safe.

Why this preserves consumer behaviour

--remove-section only drops named sections; ELF .text / .data / .bss / .symtab / .strtab / relocations are untouched. No exported symbol disappears — nm output is unchanged before / after. Native consumers (e.g. spirv-llvm-translator, the only in-distro consumer of llvm-static) keep linking normally. The only consumers that would notice the change are ones that explicitly drive clang -flto across the LLVM static libraries; there are no such consumers in Azure Linux today (verified via grep over base/comps/**/*.toml and specs/**/*.spec). llvm20-static has zero in-distro consumers, period.

Validation

• Render: clean (STATUS: ok for both components). The appended loop lands at the tail of %install, right before the %check section directive.
• Lock: refreshed input-fingerprints for both locks/llvm.lock and locks/llvm20.lock.

Estimated impact

~30–60% reduction in libLLVM*.a compressed size, which translates to a similar percentage drop in scanner-side decompression time — comfortably within the existing budget. Will be verified post-build by comparing base/out/llvm-static-*.rpm size before/after.

[github-actions]

📄❌ Rendered specs are out of date

FIX: — run this and commit the result:

azldev component render llvm llvm20

Or download the fix patch and apply it:

gh run download 25832754526 -R microsoft/azurelinux -n rendered-specs-patch
git apply rendered-specs.patch

Category	Count
Content diffs	2
Extra files (untracked)	0
Missing files (deleted)	0

Content diffs

`specs/l/llvm/llvm.spec`

--- committed/specs/l/llvm/llvm.spec
+++ rendered/specs/l/llvm/llvm.spec
@@ -3538,8 +3538,8 @@
 
 %changelog
 ## START: Generated by rpmautospec
-* Wed May 13 2026 azldev <azldev@local> - 21.1.8-8
-- Local changes (uncommitted)
+* Wed May 13 2026 Pawel Winogrodzki <pawelwi@microsoft.com> - 21.1.8-8
+- llvm, llvm20: strip LLVM-bitcode sections from libLLVM*.a archives
 
 * Mon May 11 2026 Dan Streetman <ddstreet@ieee.org> - 21.1.8-7
 - fix(llvm): remove bootstrap workarounds

`specs/l/llvm20/llvm20.spec`

--- committed/specs/l/llvm20/llvm20.spec
+++ rendered/specs/l/llvm20/llvm20.spec
@@ -3532,8 +3532,8 @@
 
 %changelog
 ## START: Generated by rpmautospec
-* Wed May 13 2026 azldev <azldev@local> - 20.1.8-6
-- Local changes (uncommitted)
+* Wed May 13 2026 Pawel Winogrodzki <pawelwi@microsoft.com> - 20.1.8-6
+- llvm, llvm20: strip LLVM-bitcode sections from libLLVM*.a archives
 
 * Mon May 11 2026 Dan Streetman <ddstreet@ieee.org> - 20.1.8-5
 - fix(llvm): remove bootstrap workarounds

[reubeno]

@PawelWMS -- I don't think we should prevent use of LTO when linking against these libraries. Is this really our option of last resort?

[PawelWMS]

Closing — the underlying scanner issue was resolved by a package-signing-pipeline update, so this component-level workaround is no longer needed. libLLVM*.a ships unmodified again.