Redefine derivations of MVK_APPLE_SILICON, MVK_MACOS_APPLE_SILICON, a…

…nd MVK_XCODE_12.

Derive MVK_APPLE_SILICON from target CPU.
Derive MVK_MACOS_APPLE_SILICON from target CPU and macOS platform.
Derive MVK_XCODE_12 from macOS and iOS SDK versions.
Test for simulator on non-Apple GPU using MVK_OS_SIMULATOR && !MVK_APPLE_SILICON.

Common/MVKCommonEnvironment.h

@@ -77,19 +77,19 @@ extern "C" {
 # define MVK_OS_SIMULATOR TARGET_OS_SIMULATOR
 #endif
 
-/** Building for macOS with support for Apple Silicon. */
-#ifndef MVK_MACOS_APPLE_SILICON
-# define MVK_MACOS_APPLE_SILICON (__MAC_OS_X_VERSION_MAX_ALLOWED >= 101600)
+/** Building for Apple Silicon on iOS, tvOS, or macOS platform. */
+#ifndef MVK_APPLE_SILICON
+# define MVK_APPLE_SILICON TARGET_CPU_ARM64
 #endif
 
-/** Building for Apple Silicon. */
-#ifndef MVK_APPLE_SILICON
-# define MVK_APPLE_SILICON (MVK_IOS || MVK_TVOS || MVK_MACOS_APPLE_SILICON)
+/** Building for macOS with support for Apple Silicon. */
+#ifndef MVK_MACOS_APPLE_SILICON
+# define MVK_MACOS_APPLE_SILICON (MVK_MACOS && MVK_APPLE_SILICON)
 #endif
 
 /** Building with Xcode 12. */
 #ifndef MVK_XCODE_12
-# define MVK_XCODE_12 (MVK_MACOS_APPLE_SILICON || \
+# define MVK_XCODE_12 ((__MAC_OS_X_VERSION_MAX_ALLOWED >= 101600) || \
  (__IPHONE_OS_VERSION_MAX_ALLOWED >= 140000)) // Also covers tvOS
 #endif
 

MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm

@@ -1546,13 +1546,9 @@
 #endif
  }
 
- // iOS and tvOS adjustments necessary when running in the simulator on non-Apple GPUs.
- // Apple1 used as baseline for detecting Apple Silicon on macOS because Apple7 not supported for tvOS.
- // Must run after setting native iOS and tvOS values above.
-#if MVK_OS_SIMULATOR
- if ( !supportsMTLGPUFamily(Apple1) ) {
- _metalFeatures.mtlBufferAlignment = 256;
- }
+// iOS and tvOS adjustments necessary when running in the simulator on non-Apple GPUs.
+#if MVK_OS_SIMULATOR && !MVK_APPLE_SILICON
+ _metalFeatures.mtlBufferAlignment = 256;
 #endif
 }