Use arm64 MSVC on arm64 Windows

distutils/_msvccompiler.py

@@ -33,7 +33,7 @@
     LibError,
     LinkError,
 )
-from .util import get_platform
+from .util import get_platform, get_host_platform
 
 
 def _find_vc2015():
@@ -178,15 +178,30 @@ def _find_exe(exe, paths=None):
     return exe
 
 
-# A map keyed by get_platform() return values to values accepted by
-# 'vcvarsall.bat'. Always cross-compile from x86 to work with the
-# lighter-weight MSVC installs that do not include native 64-bit tools.
-PLAT_TO_VCVARS = {
-    'win32': 'x86',
-    'win-amd64': 'x86_amd64',
-    'win-arm32': 'x86_arm',
-    'win-arm64': 'x86_arm64',
-}
+def _get_plat_to_vcvars():
+    # A map keyed by get_platform() return values to values accepted by
+    # 'vcvarsall.bat'.
+    if get_platform() == get_host_platform() == "win-arm64":
+        # Use the native MSVC host if the host platform would need expensive
+        # emulation for x86.
+        return {
+            'win32': 'arm64_x86',
+            'win-amd64': 'arm64_amd64',
+            'win-arm32': 'arm64_arm',
+            'win-arm64': 'arm64',
+        }
+    else:
+        # Always cross-compile from x86 to work with the lighter-weight MSVC
+        # installs that do not include native 64-bit tools.
+        return {
+            'win32': 'x86',
+            'win-amd64': 'x86_amd64',
+            'win-arm32': 'x86_arm',
+            'win-arm64': 'x86_arm64',
+        }
+
+
+PLAT_TO_VCVARS = _get_plat_to_vcvars()
 
 
 class MSVCCompiler(CCompiler):