ci: stop the LLVM caches from being evicted

The Actions cache of the repository was at 10.24 GB against a quota of
10 GB, so GitHub removed entries by least recent use. The LLVM entries
were among the first to go, and CI then built LLVM again although the
LLVM version did not change.

The Docker buildx layer blobs held 6.0 GB of the quota. All LLVM caches
together held 1.97 GB. Move the Docker layer cache to a registry cache in
GHCR, which does not use the Actions quota. Both jobs have the necessary
permission and login already.

Pin the LLVM commit in llvm-version.txt and fetch that commit, in place
of a clone of the branch tip tinygo_22.x. Add a hash of that file to each
LLVM cache key, so a change of the LLVM version invalidates the caches
and no other change does.

Also rename the LLVM image tags from llvm-20 to llvm-22.

.dockerignore

@@ -1,4 +1,4 @@
 build/
 llvm-*/
+!llvm-version.txt
 .github
-

.github/workflows/build-macos.yml

@@ -46,7 +46,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-source
         with:
-          key: llvm-source-22-${{ matrix.os }}-v1
+          key: llvm-source-22-${{ matrix.os }}-v1-${{ hashFiles('llvm-version.txt') }}
           path: |
             llvm-project/clang/lib/Headers
             llvm-project/clang/include
@@ -71,7 +71,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-build
         with:
-          key: llvm-build-22-${{ matrix.os }}-v1
+          key: llvm-build-22-${{ matrix.os }}-v1-${{ hashFiles('llvm-version.txt') }}
           path: llvm-build
       - name: Build LLVM
         if: steps.cache-llvm-build.outputs.cache-hit != 'true'

.github/workflows/compat.yml

@@ -46,7 +46,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-source
         with:
-          key: llvm-source-22-linux-compat
+          key: llvm-source-22-linux-compat-${{ hashFiles('llvm-version.txt') }}
           path: llvm-project/compiler-rt
       - name: Download LLVM source
         if: steps.cache-llvm-source.outputs.cache-hit != 'true'

.github/workflows/docker.yml

@@ -64,5 +64,5 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
-          cache-from: type=gha
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository_owner }}/tinygo-dev:buildcache
-          cache-to: type=gha,mode=max
+          cache-to: type=registry,ref=ghcr.io/${{ github.repository_owner }}/tinygo-dev:buildcache,mode=max

.github/workflows/linux.yml

@@ -66,7 +66,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-source
         with:
-          key: llvm-source-22-linux-alpine-v1
+          key: llvm-source-22-linux-alpine-v1-${{ hashFiles('llvm-version.txt') }}
           path: |
             llvm-project/clang/lib/Headers
             llvm-project/clang/include
@@ -91,7 +91,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-build
         with:
-          key: llvm-build-22-linux-alpine-v1
+          key: llvm-build-22-linux-alpine-v1-${{ hashFiles('llvm-version.txt') }}
           path: llvm-build
       - name: Build LLVM
         if: steps.cache-llvm-build.outputs.cache-hit != 'true'
@@ -268,7 +268,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-source
         with:
-          key: llvm-source-22-linux-asserts-v1
+          key: llvm-source-22-linux-asserts-v1-${{ hashFiles('llvm-version.txt') }}
           path: |
             llvm-project/clang/lib/Headers
             llvm-project/clang/include
@@ -293,7 +293,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-build
         with:
-          key: llvm-build-22-linux-asserts-v1
+          key: llvm-build-22-linux-asserts-v1-${{ hashFiles('llvm-version.txt') }}
           path: llvm-build
       - name: Build LLVM
         if: steps.cache-llvm-build.outputs.cache-hit != 'true'
@@ -377,7 +377,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-source
         with:
-          key: llvm-source-22-linux-v1
+          key: llvm-source-22-linux-v1-${{ hashFiles('llvm-version.txt') }}
           path: |
             llvm-project/clang/lib/Headers
             llvm-project/clang/include
@@ -402,7 +402,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-build
         with:
-          key: llvm-build-22-linux-${{ matrix.goarch }}-v1
+          key: llvm-build-22-linux-${{ matrix.goarch }}-v1-${{ hashFiles('llvm-version.txt') }}
           path: llvm-build
       - name: Build LLVM
         if: steps.cache-llvm-build.outputs.cache-hit != 'true'

.github/workflows/llvm.yml

@@ -35,8 +35,8 @@ jobs:
         uses: docker/metadata-action@v6
         with:
           images: |
-            tinygo/llvm-20
+            tinygo/llvm-22
-            ghcr.io/${{ github.repository_owner }}/llvm-20
+            ghcr.io/${{ github.repository_owner }}/llvm-22
           tags: |
             type=sha,format=long
             type=raw,value=latest
@@ -59,5 +59,5 @@ jobs:
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
-          cache-from: type=gha
+          cache-from: type=registry,ref=ghcr.io/${{ github.repository_owner }}/llvm-22:buildcache
-          cache-to: type=gha,mode=max
+          cache-to: type=registry,ref=ghcr.io/${{ github.repository_owner }}/llvm-22:buildcache,mode=max

.github/workflows/nix.yml

@@ -29,7 +29,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-source
         with:
-          key: llvm-source-22-linux-nix-v1
+          key: llvm-source-22-linux-nix-v1-${{ hashFiles('llvm-version.txt') }}
           path: |
             llvm-project/compiler-rt
       - name: Download LLVM source

.github/workflows/sizediff.yml

@@ -34,7 +34,7 @@ jobs:
         uses: actions/cache@v5
         id: cache-llvm-source
         with:
-          key: llvm-source-22-sizediff-v1
+          key: llvm-source-22-sizediff-v1-${{ hashFiles('llvm-version.txt') }}
           path: |
             llvm-project/compiler-rt
       - name: Download LLVM source

.github/workflows/windows.yml

@@ -40,7 +40,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-source
         with:
-          key: llvm-source-22-windows-v3
+          key: llvm-source-22-windows-v3-${{ hashFiles('llvm-version.txt') }}
           path: |
             llvm-project/clang/lib/Headers
             llvm-project/clang/include
@@ -65,7 +65,7 @@ jobs:
         uses: actions/cache/restore@v5
         id: cache-llvm-build
         with:
-          key: llvm-build-22-windows-v1
+          key: llvm-build-22-windows-v1-${{ hashFiles('llvm-version.txt') }}
           path: llvm-build
       - name: Build LLVM
         if: steps.cache-llvm-build.outputs.cache-hit != 'true'

BUILDING.md

@@ -53,6 +53,10 @@ the git repository). Then, inside the directory, download the LLVM source:
 
     make llvm-source
 
+The LLVM commit to use is pinned in `llvm-version.txt`. A change to that file
+makes CI build LLVM again, because the file is part of the LLVM cache key. All
+other changes reuse the cached LLVM build.
+
 You can also store LLVM outside of the TinyGo root directory by setting the
 `LLVM_BUILDDIR`, `CLANG_SRC` and `LLD_SRC` make variables, but that is not
 covered by this guide.

Dockerfile

@@ -11,6 +11,7 @@ RUN apt-get update && \
 
 COPY ./GNUmakefile /tinygo/GNUmakefile
 COPY ./make /tinygo/make
+COPY ./llvm-version.txt /tinygo/llvm-version.txt
 
 RUN cd /tinygo/ && \
     make llvm-source

llvm-version.txt

@@ -0,0 +1 @@
+2be7242b6a4d59fe89fb43f7d1e7333dc9b307a2

make/llvm.mk

@@ -75,8 +75,15 @@ endif
     CGO_LDFLAGS+=-L$(abspath $(LLVM_BUILDDIR)/lib) -lclang $(CLANG_LIBS) $(LLD_LIBS) $(shell $(LLVM_CONFIG_PREFIX) $(LLVM_BUILDDIR)/bin/llvm-config --ldflags --libs --system-libs $(LLVM_COMPONENTS)) -lstdc++ $(CGO_LDFLAGS_EXTRA)
 endif
 
+# Pinned in llvm-version.txt. Branch tinygo_22.x of tinygo-org/llvm-project.
+LLVM_REVISION = $(shell cat llvm-version.txt)
+
 $(LLVM_PROJECTDIR)/llvm:
-	git clone -b tinygo_22.x --depth=1 https://github.com/tinygo-org/llvm-project $(LLVM_PROJECTDIR)
+	git init $(LLVM_PROJECTDIR)
+	cd $(LLVM_PROJECTDIR) && \
+	  git remote add origin https://github.com/tinygo-org/llvm-project && \
+	  git fetch --depth=1 origin $(LLVM_REVISION) && \
+	  git checkout FETCH_HEAD
 llvm-source: $(LLVM_PROJECTDIR)/llvm ## Get LLVM sources
 
 # Configure LLVM.