Port to LLVM 22 and shift the support window to clang 12-22.

LLVM 22 reshaped clang's type and lookup machinery enough that
the port needs real wrappers, not one-liners: NestedNameSpecifier
became a uintptr value type, ElaboratedType folded into TagType,
and the ASTContext::get* / TagDecl factories rotated through new
signatures (llvm/llvm-project#147835). Compatibility.h grows the
wrappers; lib/Differentiator call sites move onto them. Older
matrix rows stay NFC -- the wrappers are no-ops there. CHECK
lines in four test files loosen for clang 22's TypePrinter drift
(spellings only, no behaviour). Build-side bits: CMake bounds
to 22.x, PassPlugin.h moved (llvm/Passes -> llvm/Plugins), and
-Wno-macro-redefined silences LLVM's duplicate
_GLIBCXX_USE_CXX11_ABI define on 22+.

Add an LLVM 22 row to CI so the new code path is actually
exercised.

clad's window covers the last 10 majors, so 11 falls off. Bump
the CMake floor to 12.0, drop the runtime11 CI row, and delete
every `#if CLANG_VERSION_MAJOR < 12` branch. Wrappers that
collapsed to one-line passthroughs get inlined at the call site
and removed -- Expr_EvaluateAsConstantExpr, CXXMemberCallExpr_Create,
SwitchStmt_Create, Sema_ActOnStartOfSwitchStmt, and five
CLAD_COMPAT_CLANG{8,12}_* macros. CallExpr_Create,
CUDAKernelCallExpr_Create and IfStmt_Create stay (too many
parameters to inline cleanly, or still version-branching for
clang 14).

Author: vgvassilev

.github/workflows/ci.yml

@@ -31,9 +31,8 @@ jobs:
       matrix:
 
         include:
-          # --- LINUX: Last 10 Runtimes (12-21) ---
+          # --- LINUX: Last 11 Runtimes (12-22) ---
           # Using Ubuntu 22.04 for older runtimes, 24.04 for newer ones
-          - { name: ubu22-gcc10-runtime11, os: ubuntu-22.04, compiler: gcc-10, clang-runtime: '11' }
           - { name: ubu22-gcc11-runtime12, os: ubuntu-22.04, compiler: gcc-11, clang-runtime: '12' }
           - { name: ubu22-clang13-runtime13, os: ubuntu-22.04, compiler: clang-13, clang-runtime: '13' }
           - { name: ubu24-gcc13-runtime14, os: ubuntu-24.04, compiler: gcc-13, clang-runtime: '14' }
@@ -44,6 +43,7 @@ jobs:
           - { name: ubu24-clang17-runtime19, os: ubuntu-24.04, compiler: clang-17, clang-runtime: '19' }
           - { name: ubu24-clang19-runtime20, os: ubuntu-24.04, compiler: clang-19, clang-runtime: '20' }
           - { name: ubu24-clang20-runtime21, os: ubuntu-24.04, compiler: clang-20, clang-runtime: '21' }
+          - { name: ubu24-clang20-runtime22, os: ubuntu-24.04, compiler: clang-20, clang-runtime: '22' }
           # --- MACOS: Last 5 Runtimes (17-21) ---
           # Using macOS ARM (standard) for all; Runtime 17 on Intel for x86 sanity
           - { name: osx-intel-runtime17, os: macos-15-intel, compiler: clang, clang-runtime: '17' }
@@ -181,25 +181,26 @@ jobs:
           fi
         fi
         echo "ncpus=$ncpus" >> $GITHUB_ENV
-    - name: Setup LLVM ${{ matrix.clang-runtime }}
+    - name: Setup LLVM ${{ matrix.clang-runtime }}${{ matrix.flavor && format(' [{0}]', matrix.flavor) || '' }}
       if: runner.os != 'Windows' && matrix.debug_build != true
       uses: compiler-research/ci-workflows/actions/setup-llvm@main
       with:
         version: ${{ matrix.clang-runtime }}
         os:      ${{ matrix.self-hosted-os || matrix.os }}
-        flavor:  system
+        flavor:  ${{ matrix.flavor || 'system' }}
 
     - name: Install extra Linux deps
-      # debug_build rows skip setup-llvm and never get apt-llvm.org, so
-      # libomp-N-dev past the noble archive cap is unreachable. OpenMP
-      # lit tests then skip on the debug row; other rows still cover them.
       if: runner.os == 'Linux' && matrix.debug_build != true
       run: |
-        # setup-llvm covers llvm-N-dev + clang-N + libclang-N-dev +
-        # libclang-rt-N-dev. Pick up libomp and per-row extras here.
         # cmake is preinstalled on github-hosted ubuntu-24.04 but absent
         # from catthehacker/ubuntu:act-24.04; install it so bin/repro works.
-        sudo apt install -y cmake libomp-${{ matrix.clang-runtime }}-dev ${{ matrix.extra_packages }}
+        sudo apt install -y cmake ${{ matrix.extra_packages }}
+        # libomp-N-dev: best-effort. apt-llvm.org lags on the latest
+        # major; recipe-flavor rows get libomp from the recipe build,
+        # not apt. When missing, OpenMP lit tests skip via REQUIRES.
+        if apt-cache show "libomp-${{ matrix.clang-runtime }}-dev" >/dev/null 2>&1; then
+          sudo apt install -y "libomp-${{ matrix.clang-runtime }}-dev"
+        fi
 
     - name: Setup compiler on Linux
       if: runner.os == 'Linux'
@@ -328,12 +329,13 @@ jobs:
     - name: Setup LLVM/Clang on Linux
       if: ${{ (runner.os == 'Linux') && (matrix.debug_build != true) }}
       run: |
-        UNIX_DISTRO=$(lsb_release -rs)
-        PATH_TO_LLVM_BUILD=/usr/lib/llvm-${{ matrix.clang-runtime }}/
-        # Add -H to silence 'The directory '/home/..../pip/http' or its parent
-        # directory is not owned by the current user and the cache has been disabled.
+        # setup-llvm always lands the install at $GITHUB_WORKSPACE/install
+        # (a symlink to /usr/lib/llvm-N for flavor=system, a real install
+        # tree for the recipe flavors). Point clad's build prefix there so
+        # the cmake configs and their .a references resolve regardless of
+        # flavor.
+        PATH_TO_LLVM_BUILD="$GITHUB_WORKSPACE/install"
         pip3 install lit # LLVM lit is not part of the llvm releases...
-        # We need PATH_TO_LLVM_BUILD later
         echo "PATH_TO_LLVM_BUILD=$PATH_TO_LLVM_BUILD" >> $GITHUB_ENV
     - name: Setup LLVM/Clang on Windows
       if: ${{ runner.os == 'windows' }}

CMakeLists.txt

@@ -37,12 +37,12 @@ set(CMAKE_MODULE_PATH
   )
 
 # Define clad supported version of clang and llvm.
-set(CLANG_MIN_SUPPORTED 11.0)
-set(CLANG_MAX_SUPPORTED "21.2.x")
-set(CLANG_VERSION_UPPER_BOUND 21.2.0)
-set(LLVM_MIN_SUPPORTED 11.0)
-set(LLVM_MAX_SUPPORTED "21.2.x")
-set(LLVM_VERSION_UPPER_BOUND 21.2.0)
+set(CLANG_MIN_SUPPORTED 12.0)
+set(CLANG_MAX_SUPPORTED "22.2.x")
+set(CLANG_VERSION_UPPER_BOUND 22.2.0)
+set(LLVM_MIN_SUPPORTED 12.0)
+set(LLVM_MAX_SUPPORTED "22.2.x")
+set(LLVM_VERSION_UPPER_BOUND 22.2.0)
 
 # If we are not building as a part of LLVM, build clad as an
 # standalone project, using LLVM as an external library:
@@ -187,6 +187,13 @@ if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
 
   add_definitions(${LLVM_DEFINITIONS})
 
+  # LLVM 22 sets _GLIBCXX_USE_CXX11_ABI twice (HandleLLVMOptions +
+  # LLVMConfig), which trips -Werror=macro-redefined. Suppress that
+  # specific warning -- it's an upstream duplication, not a code bug.
+  if (LLVM_VERSION_MAJOR GREATER_EQUAL 22)
+    add_compile_options(-Wno-macro-redefined)
+  endif()
+
   set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib/)
   set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin/)