squash! ci : add ccache to build-wasm

Debugging...

Author: danbev

.github/workflows/build-wasm.yml

@@ -55,8 +55,50 @@ jobs:
       - name: Build
         env:
           CCACHE_SLOPPINESS: time_macros
+          CCACHE_LOGFILE: /tmp/ccache.log
         run: |
           emcmake cmake -B build -DCMAKE_BUILD_TYPE=${{ matrix.build }} \
             -DCMAKE_C_COMPILER_LAUNCHER=ccache \
             -DCMAKE_CXX_COMPILER_LAUNCHER=ccache
           cmake --build build -j $(nproc)
+
+      - name: ccache log (ggml.cpp first miss)
+        run: |
+          echo "=== ccache stats ==="
+          ccache -s
+          echo "=== all Result lines ==="
+          grep "Result:" /tmp/ccache.log | head -20
+          echo "=== first ggml.cpp invocation ==="
+          awk '/ggml\.cpp\.o/{found=1} found{print; if(/Result:/) exit}' /tmp/ccache.log | head -80
+
+      - name: emcc -E determinism check
+        run: |
+          # Use real flags from cmake's compile_commands.json for ggml.cpp
+          FLAGS=$(python3 -c "
+          import json, sys
+          db = json.load(open('build/compile_commands.json'))
+          for e in db:
+              if 'ggml.cpp.o' in e['output'] and 'ggml-base' in e['output']:
+                  # extract flags, drop -o/-c/-MD/-MF/-MT and their args
+                  import shlex
+                  args = shlex.split(e['command'])[1:]  # drop compiler
+                  out = []
+                  skip = False
+                  for a in args:
+                      if skip: skip=False; continue
+                      if a in ('-o','-MF','-MT'): skip=True; continue
+                      if a in ('-c','-MD'): continue
+                      if a.endswith('.cpp'): continue
+                      out.append(a)
+                  print(' '.join(out))
+                  sys.exit(0)
+          " 2>/dev/null || echo "-I ggml/include")
+          echo "Preprocessing flags: $FLAGS"
+          emcc -E $FLAGS ggml/src/ggml.cpp -o /tmp/pp1.cpp 2>/dev/null
+          emcc -E $FLAGS ggml/src/ggml.cpp -o /tmp/pp2.cpp 2>/dev/null
+          if diff -q /tmp/pp1.cpp /tmp/pp2.cpp > /dev/null 2>&1; then
+            echo "DETERMINISTIC: emcc -E produces identical output for consecutive runs"
+          else
+            echo "NON-DETERMINISTIC: diff follows (first 30 lines):"
+            diff /tmp/pp1.cpp /tmp/pp2.cpp | head -30
+          fi