feat: MSVC auto-detection + C compiler check before torch.compile

CorridorKeyModule/inference_engine.py

@@ -24,6 +24,31 @@
 logger = logging.getLogger(__name__)
 
 
+def _try_activate_msvc() -> None:
+    """Find and activate MSVC (cl.exe) on Windows if installed but not in PATH.
+
+    Searches common Visual Studio install locations for the latest cl.exe
+    and adds its directory to PATH.
+    """
+    import glob
+
+    patterns = [
+        r"C:\Program Files\Microsoft Visual Studio\2022\*\VC\Tools\MSVC\*\bin\Hostx64\x64\cl.exe",
+        r"C:\Program Files (x86)\Microsoft Visual Studio\2022\*\VC\Tools\MSVC\*\bin\Hostx64\x64\cl.exe",
+        r"C:\Program Files\Microsoft Visual Studio\2019\*\VC\Tools\MSVC\*\bin\Hostx64\x64\cl.exe",
+    ]
+
+    for pattern in patterns:
+        matches = sorted(glob.glob(pattern), reverse=True)  # newest version first
+        if matches:
+            cl_dir = os.path.dirname(matches[0])
+            os.environ["PATH"] = cl_dir + os.pathsep + os.environ.get("PATH", "")
+            logger.info("Auto-detected MSVC: %s", matches[0])
+            return
+
+    logger.debug("MSVC not found in standard locations")
+
+
 class CorridorKeyEngine:
     def __init__(
         self,
@@ -58,12 +83,29 @@ def __init__(
         self._is_rocm = hasattr(torch.version, "hip") and torch.version.hip
         self.model = self._load_model()
 
-        # torch.compile is tested on CUDA (Windows + Linux) and ROCm (Linux).
-        # ROCm on Windows hangs during Triton kernel compilation — skip it.
-        # CORRIDORKEY_SKIP_COMPILE=1 forces eager mode (useful for testing).
-        skip_compile = (self._is_rocm and sys.platform == "win32") or os.environ.get("CORRIDORKEY_SKIP_COMPILE") == "1"
-        if skip_compile:
-            logger.info("Skipping torch.compile (eager mode)")
+        # torch.compile needs: cl.exe (Windows), gcc (Linux), and Triton.
+        # Check prerequisites and skip with a helpful message if missing.
+        import shutil
+
+        # Auto-detect MSVC on Windows — it's installed but not in PATH by default
+        if sys.platform == "win32" and not shutil.which("cl"):
+            _try_activate_msvc()
+
+        skip_reason = None
+        if self._is_rocm and sys.platform == "win32":
+            skip_reason = "ROCm on Windows — Triton compilation hangs"
+        elif os.environ.get("CORRIDORKEY_SKIP_COMPILE") == "1":
+            skip_reason = "CORRIDORKEY_SKIP_COMPILE=1"
+        elif sys.platform == "win32" and not shutil.which("cl"):
+            skip_reason = (
+                "MSVC (cl.exe) not found. Install Visual Studio Build Tools "
+                "for ~30% faster inference: https://visualstudio.microsoft.com/visual-cpp-build-tools/"
+            )
+        elif sys.platform == "linux" and not shutil.which("gcc") and not shutil.which("cc"):
+            skip_reason = "no C compiler found — install gcc for faster inference"
+
+        if skip_reason:
+            logger.info("Skipping torch.compile (%s)", skip_reason)
         elif sys.platform == "linux" or sys.platform == "win32":
             self._compile()