Auto merge of #103894 - mati865:gnullvm-libunwind-changes, r=thomcc

Change the way libunwind is linked for *-windows-gnullvm targets

I have no idea why previous way works for `x86_64-fortanix-unknown-sgx` (assuming it actually works...) but not for `gnullvm`. It fails when linking libtest during Rust build (unless somebody adds `RUSTFLAGS='-Clinkarg=-lunwind'`).
Also fixes exception handling on AArch64.

Author: bors

std/src/personality/gcc.rs

@@ -219,7 +219,7 @@ cfg_if::cfg_if! {
         }
 
         cfg_if::cfg_if! {
-            if #[cfg(all(windows, target_arch = "x86_64", target_env = "gnu"))] {
+            if #[cfg(all(windows, any(target_arch = "aarch64", target_arch = "x86_64"), target_env = "gnu"))] {
                 // On x86_64 MinGW targets, the unwinding mechanism is SEH however the unwind
                 // handler data (aka LSDA) uses GCC-compatible encoding.
                 #[lang = "eh_personality"]

unwind/src/lib.rs

@@ -103,7 +103,3 @@ extern "C" {}
 #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))]
 #[link(name = "unwind", kind = "static", modifiers = "-bundle")]
 extern "C" {}
-
-#[cfg(all(target_os = "windows", target_env = "gnu", target_abi = "llvm"))]
-#[link(name = "unwind", kind = "static", modifiers = "-bundle")]
-extern "C" {}

unwind/src/libunwind.rs

@@ -36,9 +36,12 @@ pub const unwinder_private_data_size: usize = 20;
 #[cfg(all(target_arch = "arm", any(target_os = "ios", target_os = "watchos")))]
 pub const unwinder_private_data_size: usize = 5;
 
-#[cfg(all(target_arch = "aarch64", target_pointer_width = "64"))]
+#[cfg(all(target_arch = "aarch64", target_pointer_width = "64", not(target_os = "windows")))]
 pub const unwinder_private_data_size: usize = 2;
 
+#[cfg(all(target_arch = "aarch64", target_pointer_width = "64", target_os = "windows"))]
+pub const unwinder_private_data_size: usize = 6;
+
 #[cfg(all(target_arch = "aarch64", target_pointer_width = "32"))]
 pub const unwinder_private_data_size: usize = 5;
 
@@ -90,7 +93,10 @@ pub type _Unwind_Exception_Cleanup_Fn =
 // rustc_codegen_ssa::src::back::symbol_export, rustc_middle::middle::exported_symbols
 // and RFC 2841
 #[cfg_attr(
-    all(feature = "llvm-libunwind", any(target_os = "fuchsia", target_os = "linux")),
+    any(
+        all(feature = "llvm-libunwind", any(target_os = "fuchsia", target_os = "linux")),
+        all(target_os = "windows", target_env = "gnu", target_abi = "llvm")
+    ),
     link(name = "unwind", kind = "static", modifiers = "-bundle")
 )]
 extern "C-unwind" {