Improve JIT behavior on unsupported platforms

Summary:
If trying to run on an unsupported CPU architecture, actually emit a debug print
that says what the problem is.  Currently the DLOG is always silenced.

Also catch exceptions from asmjit if we do ever get that far.  Otherwise the
entire Python runtime will crash.  This way importing CinderX will raise a
RuntimeError instead.

Reviewed By: DinoV

Differential Revision: D84076101

fbshipit-source-id: 4114ce5e038fad22ca0740c693fb6bb8cb72410f

Author: alexmalyshev

cinderx/Jit/pyjit.cpp

@@ -2789,6 +2789,22 @@ void finalizeInternedStrings() {
   }
 }
 
+constexpr std::string_view getCpuArchName() {
+#if defined(__x86_64__)
+  return "x86-64";
+#elif defined(__i386__)
+  return "x86 (32-bit)";
+#elif defined(__aarch64__)
+  return "arm64";
+#elif defined(__arm__)
+  return "arm";
+#elif defined(__riscv)
+  return "riscv";
+#else
+  return "unknown";
+#endif
+}
+
 } // namespace
 
 #if PY_VERSION_HEX < 0x030C0000
@@ -2964,6 +2980,15 @@ int initialize() {
     return 0;
   }
 
+  // Do this check after config is initialized, so we can use JIT_DLOG().
+#ifndef __x86_64__
+  JIT_DLOG(
+      "JIT only supported x86-64 platforms, detected current architecture as "
+      "'{}'. Disabling the JIT.",
+      getCpuArchName());
+  return 0;
+#endif
+
   std::unique_ptr<JITList> jit_list;
   if (!getConfig().jit_list.filename.empty()) {
     if (getConfig().allow_jit_list_wildcards) {
@@ -2992,7 +3017,14 @@ int initialize() {
   cinderx::ModuleState* mod_state = cinderx::getModuleState();
   mod_state->setCodeAllocator(CodeAllocator::make());
 
-  cinderx::getModuleState()->setJitContext(new CompilerContext<Compiler>());
+  // Initialize the main compiler object and its context.  This will throw if
+  // asmjit cannot initialize.
+  try {
+    cinderx::getModuleState()->setJitContext(new CompilerContext<Compiler>());
+  } catch (const std::exception& exn) {
+    PyErr_SetString(PyExc_RuntimeError, exn.what());
+    return -1;
+  }
 
   PyObject* mod = _Ci_CreateBuiltinModule(&jit_module, "cinderjit");
   if (mod == nullptr) {