Start adding an `aarch64-pc-windows-msvc` target

This commit adds the necessary definitions for target specs and such as well as
the necessary support in libstd to compile basic `aarch64-pc-windows-msvc`
binaries. The target is not currently built on CI, but it can be built locally
with:

    ./configure --target=aarch64-pc-windows-msvc --set rust.lld
    ./x.py build src/libstd --target aarch64-pc-windows-msvc

Currently this fails to build `libtest` due to a linker bug (seemingly in LLD?)
which hasn't been investigate yet. Otherwise though with libstd you can build a
hello world program (linked with LLD). I've not tried to execute it yet, but it
at least links!

Full support for this target is still a long road ahead, but this is hopefully a
good stepping stone to get started.

Points of note about this target are:

* Currently defaults to `panic=abort` as support is still landing in LLVM for
  SEH on AArch64.
* Currently defaults to LLD as a linker as I was able to get farther with it
  than I was with `link.exe`

1 files changed, 24 insertions, 0 deletions

diff --git a/src/libstd/sys/windows/backtrace/mod.rs b/src/libstd/sys/windows/backtrace/mod.rs
index 7ef4e203571..f64cae810b9 100644
--- a/src/libstd/sys/windows/backtrace/mod.rs
+++ b/src/libstd/sys/windows/backtrace/mod.rs
@@ -229,6 +229,7 @@ impl StackFrame for c::STACKFRAME_EX {
         self.AddrFrame.Mode = c::ADDRESS_MODE::AddrModeFlat;
         c::IMAGE_FILE_MACHINE_I386
     }
+
     #[cfg(target_arch = "x86_64")]
     fn init(&mut self, ctx: &c::CONTEXT) -> c::DWORD {
         self.AddrPC.Offset = ctx.Rip as u64;
@@ -240,6 +241,17 @@ impl StackFrame for c::STACKFRAME_EX {
         c::IMAGE_FILE_MACHINE_AMD64
     }
 
+    #[cfg(target_arch = "aarch64")]
+    fn init(&mut self, ctx: &c::CONTEXT) -> c::DWORD {
+        self.AddrPC.Offset = ctx.Pc as u64;
+        self.AddrPC.Mode = c::ADDRESS_MODE::AddrModeFlat;
+        self.AddrStack.Offset = ctx.Sp as u64;
+        self.AddrStack.Mode = c::ADDRESS_MODE::AddrModeFlat;
+        self.AddrFrame.Offset = ctx.Fp as u64;
+        self.AddrFrame.Mode = c::ADDRESS_MODE::AddrModeFlat;
+        c::IMAGE_FILE_MACHINE_ARM64
+    }
+
     fn get_addr(&self) -> *const u8 {
         (self.AddrPC.Offset - 1) as *const u8
     }
@@ -260,6 +272,7 @@ impl StackFrame for c::STACKFRAME64 {
         self.AddrFrame.Mode = c::ADDRESS_MODE::AddrModeFlat;
         c::IMAGE_FILE_MACHINE_I386
     }
+
     #[cfg(target_arch = "x86_64")]
     fn init(&mut self, ctx: &c::CONTEXT) -> c::DWORD {
         self.AddrPC.Offset = ctx.Rip as u64;
@@ -271,6 +284,17 @@ impl StackFrame for c::STACKFRAME64 {
         c::IMAGE_FILE_MACHINE_AMD64
     }
 
+    #[cfg(target_arch = "aarch64")]
+    fn init(&mut self, ctx: &c::CONTEXT) -> c::DWORD {
+        self.AddrPC.Offset = ctx.Pc as u64;
+        self.AddrPC.Mode = c::ADDRESS_MODE::AddrModeFlat;
+        self.AddrStack.Offset = ctx.Sp as u64;
+        self.AddrStack.Mode = c::ADDRESS_MODE::AddrModeFlat;
+        self.AddrFrame.Offset = ctx.Fp as u64;
+        self.AddrFrame.Mode = c::ADDRESS_MODE::AddrModeFlat;
+        c::IMAGE_FILE_MACHINE_ARM64
+    }
+
     fn get_addr(&self) -> *const u8 {
         (self.AddrPC.Offset - 1) as *const u8
     }