unity-dotnet P5 JIT: embed passes with virtual calls JITted (431 methods, 0 invalid)

The interpreter's vcall/PIC/AOT-vcall caches pack pointers into 32-bit
halves; on 64-bit they are off and the miss path resolves through
get_virtual_method_fast. Call args and the return register are coerced
to the callee's/function's type where a native-int vreg was widened to
i64. Adds CTTZ32/64 and LCONV_TO_[IU][12] (64-bit keeps them).
GEX_NO_SIGNAL_TRAPS=1 makes wasmtime use explicit bounds checks
(backtrace on a wild address).

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01PeRutwFgZ66XpxjasKrPn1

shims/native/src/lib.rs

@@ -658,6 +658,12 @@ pub fn engine() -> Result<Engine> {
         config.wasm_memory64(true);
         config.memory_reservation(gex_abi::LIMIT64);
     }
+    // `GEX_NO_SIGNAL_TRAPS=1` (debugging): explicit bounds checks, so a wild address in generated code traps
+    // with a backtrace instead of faulting outside every guard region (which the signal handler cannot
+    // attribute and the process dies of).
+    if std::env::var_os("GEX_NO_SIGNAL_TRAPS").is_some() {
+        config.signals_based_traps(false);
+    }
     // gex's output is already optimised; Cranelift only adds register
     // allocation and peepholes, whose time dominates on a large program (half
     // a minute to compile SQLite vs under two seconds to translate).