Merge pull request #1273 from billhollings/simulator-buffer-alignment

Set Metal buffer alignment to 256 on non-Apple Silicon iOS/tvOS simulators.

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

@@ -1428,7 +1428,7 @@
  if (supportsMTLGPUFamily(Apple5)) {
  // This is an Apple GPU--treat it accordingly.
  _metalFeatures.mtlCopyBufferAlignment = 1;
- _metalFeatures.mtlBufferAlignment = 16;
+ _metalFeatures.mtlBufferAlignment = 16; // Min float4 alignment for typical vertex buffers. MTLBuffer may go down to 4 bytes for other data.
  _metalFeatures.maxQueryBufferSize = (64 * KIBI);
  _metalFeatures.maxPerStageDynamicMTLBufferCount = _metalFeatures.maxPerStageBufferCount;
  _metalFeatures.postDepthCoverage = true;
@@ -1545,6 +1545,11 @@
  break;
 #endif
  }
+
+// 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
 }
 
 // Initializes the physical device features of this instance.