IGL: Apply iOS 16 fix to instanced drawing

Summary: This is a quick attempt to fix more issues related to instanced drawing in IGL. This feature is only available in newer GPUs. We're using iOS 16 as a proxy for these features being available. Later diffs will apply a proper fix.

Reviewed By: anthonydito

Differential Revision: D52606631

fbshipit-source-id: 2cb586429c4a6397266b5da2463e4f2b0615afdf

src/igl/metal/RenderCommandEncoder.mm

@@ -349,11 +349,19 @@
   getCommandBuffer().incrementCurrentDrawCount();
   IGL_ASSERT(encoder_);
   MTLPrimitiveType metalPrimitive = convertPrimitiveType(primitiveType);
-  [encoder_ drawPrimitives:metalPrimitive
-               vertexStart:vertexStart
-               vertexCount:vertexCount
-             instanceCount:instanceCount
-              baseInstance:baseInstance];
+#if IGL_PLATFORM_IOS
+  if (@available(iOS 16, *)) {
+#endif // IGL_PLATFORM_IOS
+    [encoder_ drawPrimitives:metalPrimitive
+                 vertexStart:vertexStart
+                 vertexCount:vertexCount
+               instanceCount:instanceCount
+                baseInstance:baseInstance];
+#if IGL_PLATFORM_IOS
+  } else {
+    [encoder_ drawPrimitives:metalPrimitive vertexStart:vertexStart vertexCount:vertexCount];
+  }
+#endif // IGL_PLATFORM_IOS
 }
 
 void RenderCommandEncoder::drawIndexed(PrimitiveType primitiveType,