Initial work to build for Windows ARM64 (bytecodealliance#4990)

* Make wasmtime build for windows-aarch64

* Add check for win arm64 build.

* Fix checks for winarm64 key in workflows.

* Add target in windows arm64 build.

* Add tracking issue for Windows ARM64 trap handling

.github/workflows/main.yml

@@ -183,6 +183,20 @@ jobs:
     - run: cargo check --target wasm32-unknown-emscripten -p wasi-common
     - run: cargo check --target armv7-unknown-linux-gnueabihf -p wasi-common
 
+  # Check whether `wasmtime` cross-compiles to aarch64-pc-windows-msvc
+  # We don't build nor test it because it lacks trap handling.
+  # Tracking issue: https://github.com/bytecodealliance/wasmtime/issues/4992
+  checks_winarm64:
+    name: Check Windows ARM64
+    runs-on: windows-latest
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        submodules: true
+    - uses: ./.github/actions/install-rust
+    - run: rustup target add aarch64-pc-windows-msvc
+    - run: cargo check -p wasmtime --target aarch64-pc-windows-msvc
+
   fuzz_targets:
     name: Fuzz Targets
     runs-on: ubuntu-latest

crates/jit/src/unwind.rs

@@ -5,6 +5,9 @@ cfg_if::cfg_if! {
     } else if #[cfg(all(windows, target_arch = "x86"))] {
         mod winx32;
         pub use self::winx32::*;
+    } else if #[cfg(all(windows, target_arch = "aarch64"))] {
+        mod winx64;
+        pub use self::winx64::*;
     } else if #[cfg(unix)] {
         mod systemv;
         pub use self::systemv::*;

crates/jit/src/unwind/winx64.rs

@@ -21,7 +21,7 @@ impl UnwindRegistration {
         if RtlAddFunctionTable(
             unwind_info as *mut _,
             (unwind_len / unit_len) as u32,
-            base_address as u64,
+            base_address as _,
         ) == 0
         {
             bail!("failed to register function table");

crates/runtime/src/traphandlers/windows.rs

@@ -58,6 +58,9 @@ unsafe extern "system" fn exception_handler(exception_info: *mut EXCEPTION_POINT
             } else if #[cfg(target_arch = "x86")] {
                 let ip = (*(*exception_info).ContextRecord).Eip as *const u8;
                 let fp = (*(*exception_info).ContextRecord).Ebp as usize;
+            } else if #[cfg(target_arch = "aarch64")] {
+                let ip = (*(*exception_info).ContextRecord).Pc as *const u8;
+                let fp = (*(*exception_info).ContextRecord).Anonymous.Anonymous.Fp as usize;
             } else {
                 compile_error!("unsupported platform");
             }