chore: Cache random stuff (#118)

* Be a bit more aggressive with caching

.github/workflows/enzyme-ci.yml

@@ -45,6 +45,20 @@ jobs:
         with:
           path: build/build/x86_64-unknown-linux-gnu/enzyme
           key: ${{ matrix.os }}-enzyme-${{ steps.enzyme-commit.outputs.HEAD }}
+      - name: Cache bootstrap/stage0 artifacts for incremental builds
+        uses: actions/cache@v4
+        with:
+          path: |
+            build/build/bootstrap/
+            build/build/x86_64-unknown-linux-gnu/stage0-rustc/
+            build/build/x86_64-unknown-linux-gnu/stage0-std/
+            build/build/x86_64-unknown-linux-gnu/stage0-tools/
+            build/build/x86_64-unknown-linux-gnu/stage1-std/
+          # Approximate stable hash. It doesn't matter too much when this goes out of sync as it just caches
+          # some stage0/stage1 dependencies and stdlibs which *hopefully* are hash-keyed.
+          key: enzyme-rust-incremental-${{ runner.os }}-${{ hashFiles('src/**/Cargo.lock', 'Cargo.lock') }}
+          restore-keys: |
+            enzyme-rust-incremental-${{ runner.os }}
       - name: Build
         run: |
           wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key|sudo apt-key add -

src/bootstrap/src/core/build_steps/llvm.rs

@@ -1211,7 +1211,12 @@ impl HashStamp {
 
     fn is_done(&self) -> bool {
         match fs::read(&self.path) {
-            Ok(h) => self.hash.as_deref().unwrap_or(b"") == h.as_slice(),
+            Ok(h) => {
+                let unwrapped = self.hash.as_deref().unwrap_or(b"");
+                let res = unwrapped == h.as_slice();
+                eprintln!("Result for {:?}: {res:?} for expected '{unwrapped:?}' and read '{h:?}'", self.path);
+                res
+            },
             Err(e) if e.kind() == io::ErrorKind::NotFound => false,
             Err(e) => {
                 panic!("failed to read stamp file `{}`: {}", self.path.display(), e);

src/bootstrap/src/lib.rs

@@ -1866,6 +1866,9 @@ pub fn generate_smart_stamp_hash(dir: &Path, additional_input: &str) -> String {
         .map(|o| String::from_utf8(o.stdout).unwrap_or_default())
         .unwrap_or_default();
 
+    eprintln!("Computing stamp for {dir:?}");
+    eprintln!("Diff output: {diff:?}");
+
     let status = Command::new("git")
         .current_dir(dir)
         .arg("status")
@@ -1876,13 +1879,19 @@ pub fn generate_smart_stamp_hash(dir: &Path, additional_input: &str) -> String {
         .map(|o| String::from_utf8(o.stdout).unwrap_or_default())
         .unwrap_or_default();
 
+    eprintln!("Status output: {status:?}");
+    eprintln!("Additional input: {additional_input:?}");
     let mut hasher = sha2::Sha256::new();
 
     hasher.update(diff);
     hasher.update(status);
     hasher.update(additional_input);
 
-    hex_encode(hasher.finalize().as_slice())
+    let result = hex_encode(hasher.finalize().as_slice());
+
+    eprintln!("Final hash: {result:?}");
+
+    result
 }
 
 /// Ensures that the behavior dump directory is properly initialized.