Fix Metal accuracy problem caused by <dtype>3 vectors usage

src/target/source/codegen_metal.cc

@@ -178,6 +178,17 @@ void CodeGenMetal::PrintType(DataType t, std::ostream& os) {  // NOLINT(*)
   }
   bool fail = false;
   if (t.is_float()) {
+    // Need to care about sizes and alignment of half3/float3 because tir representation might not
+    // be aware of Metal half3/float3 details and can treat them as just three elements,
+    // while sizes and alignmnents of half3/float3 are one element more (half3-8 bytes/
+    // float13 - 16bytes).
+    // Example of problematic pattern: filling of threadgroup packed array using float3 elements
+    // by threads concurrently can lead to datarace and wrong data in threadgroup shared array.
+    // packed_(half3/float3) are exactly datatypes dealing with 3 elements and per-element
+    // alignment
+    if (lanes == 3) {
+      os << "packed_";
+    }
     switch (t.bits()) {
       case 16:
         os << "half";