Ensure Xcode simulator always uses 256B buffer alignment.

Xcode simulator always requires 256B buffer alignment, even when running
on Apple Silicon. Previously, it was assumed that Apple Silicon would use
it's native 16B buffer alignment.

Docs/Whats_New.md

@@ -28,9 +28,10 @@ Released TBD
 - Add support for `VK_PRIMITIVE_TOPOLOGY_TRIANGLE_FAN`.
 - Support building MoltenVK for visionOS.
 - Ensure non-dispatch compute commands don't interfere with compute encoding state used by dispatch commands.
-- Support `VK_PRESENT_MODE_IMMEDIATE_KHR` if `VkPresentTimeGOOGLE::desiredPresentTime` is zero.
 - Support maximizing the concurrent executing compilation tasks via `MVKConfiguration::shouldMaximizeConcurrentCompilation`
+- Support `VK_PRESENT_MODE_IMMEDIATE_KHR` if `VkPresentTimeGOOGLE::desiredPresentTime` is zero.
 - Add support for `VK_PRESENT_MODE_IMMEDIATE_KHR` to macOS Cube demo.
+- Ensure Xcode simulator always uses 256B buffer alignment.
 - Log more info about SPIR-V to MSL conversion errors.
 - Drop official support for using *Xcode 11* to build MoltenVK.
 

MoltenVK/MoltenVK/GPUObjects/MVKDevice.mm

@@ -2157,9 +2157,9 @@ void MVKPhysicalDevice::initMetalFeatures() {
 #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;
+// iOS and tvOS adjustments necessary when running on the simulator.
+#if MVK_OS_SIMULATOR
+	_metalFeatures.mtlBufferAlignment = 256;	// Even on Apple Silicon
 #endif
 
 	// Currently, Metal argument buffer support is in beta stage, and is only supported