Support LLVM 21.0 (development branch) (#15771)

Currently, Crystal waits until a new stable major version of LLVM is released before that version is declared in `src/llvm/ext/llvm-versions.txt`, the list of supported LLVM versions. This has proved to be a hassle when maintaining Crystal on software repositories that only distribute the latest versions of each package; LLVM x.1 is often scheduled half to a whole month before a corresponding Crystal 1.y release, during which either Crystal does not run at all (LLVM could use versioned library names), or someone has to explicitly backport LLVM support on our master branch to a preceding Crystal package.

With this change, Crystal now supports the latest LLVM development branch explicitly, in the hopes that unattended transitions from LLVM x.0 to x.1 are smooth. This also means Crystal is now responsible for tracking any upstream LLVM changes as soon as possible.

Author: HertzDevil

.github/workflows/llvm.yml

@@ -41,17 +41,22 @@ jobs:
           - {llvm_version: 18, runs-on: ubuntu-24.04, codename: noble}
           - {llvm_version: 19, runs-on: ubuntu-24.04, codename: noble}
           - {llvm_version: 20, runs-on: ubuntu-24.04, codename: noble}
-    name: "LLVM ${{ matrix.llvm_version }}"
+          - {runs-on: ubuntu-24.04, codename: noble}
+    name: "LLVM ${{ matrix.llvm_version || 'Nightly' }}"
     steps:
       - name: Checkout Crystal source
         uses: actions/checkout@v4
 
-      - name: Install LLVM ${{ matrix.llvm_version }}
+      - name: Install LLVM ${{ matrix.llvm_version || 'Nightly' }}
         run: |
           sudo apt remove 'llvm-*' 'libllvm*'
           wget -qO- https://apt.llvm.org/llvm-snapshot.gpg.key | sudo tee /etc/apt/trusted.gpg.d/apt.llvm.org.asc
-          sudo apt-add-repository -y deb http://apt.llvm.org/${{ matrix.codename }}/ llvm-toolchain-${{ matrix.codename }}-${{ matrix.llvm_version }} main
-          sudo apt install -y llvm-${{ matrix.llvm_version }}-dev lld
+          sudo apt-add-repository -y \
+            deb \
+            http://apt.llvm.org/${{ matrix.codename }}/ \
+            llvm-toolchain-${{ matrix.codename }}${{ matrix.llvm_version && format('-{0}', matrix.llvm_version) || '' }} \
+            main
+          sudo apt install -y llvm${{ matrix.llvm_version && format('-{0}', matrix.llvm_version) || '' }}-dev lld
 
       - name: Install Crystal
         uses: crystal-lang/install-crystal@v1

src/compiler/crystal/codegen/codegen.cr

@@ -2544,7 +2544,7 @@ module Crystal
       name = "'#{name}'"
       key = StringKey.new(@llvm_mod, str)
       @strings[key] ||= begin
-        global = @llvm_mod.globals.add(@llvm_typer.llvm_string_type(str.bytesize), name)
+        global = @llvm_mod.globals.add(@llvm_typer.llvm_string_type(str.bytesize), name.gsub('\\', "\\\\"))
         global.linkage = LLVM::Linkage::Private
         global.global_constant = true
         global.initializer = llvm_context.const_struct [

src/llvm/enums.cr

@@ -57,6 +57,7 @@ module LLVM
     WillReturn
     WriteOnly
     ZExt
+    Captures
 
     # NOTE: enum body does not allow `class_getter` or `TypeDeclaration`, hence
     # the nil cast
@@ -91,6 +92,7 @@ module LLVM
       kinds[ArgMemOnly] = kind_for_name("argmemonly")
       kinds[Builtin] = kind_for_name("builtin")
       kinds[ByVal] = kind_for_name("byval")
+      kinds[Captures] = kind_for_name("captures")
       kinds[Cold] = kind_for_name("cold")
       kinds[Convergent] = kind_for_name("convergent")
       kinds[Dereferenceable] = kind_for_name("dereferenceable")

src/llvm/ext/llvm-versions.txt

@@ -1 +1 @@
-20.1 19.1 18.1 17.0 16.0 15.0 14.0 13.0 12.0 11.1 11.0 10.0 9.0 8.0
+21.0 20.1 19.1 18.1 17.0 16.0 15.0 14.0 13.0 12.0 11.1 11.0 10.0 9.0 8.0