[mlir][EmitC] Do not convert illegal types in EmitC

This patch adds check for unsupported types in emitc, which
fixes a crash.

Author: CoTinker

mlir/lib/Conversion/MemRefToEmitC/MemRefToEmitC.cpp

@@ -177,7 +177,8 @@ void mlir::populateMemRefToEmitCTypeConversion(TypeConverter &typeConverter) {
         }
         Type convertedElementType =
             typeConverter.convertType(memRefType.getElementType());
-        if (!convertedElementType)
+        if (!convertedElementType ||
+            !emitc::isSupportedEmitCType(convertedElementType))
           return {};
         return emitc::ArrayType::get(memRefType.getShape(),
                                      convertedElementType);

mlir/test/Conversion/MemRefToEmitC/memref-to-emitc-failed.mlir

@@ -43,3 +43,19 @@ func.func @zero_rank() {
 
 // expected-error@+1 {{failed to legalize operation 'memref.global'}}
 memref.global "nested" constant @nested_global : memref<3x7xf32>
+
+// -----
+
+func.func @unsupported_type_f16() {
+  // expected-error@+1 {{failed to legalize operation 'memref.alloca'}}
+  %0 = memref.alloca() : memref<4xf16>
+  return
+}
+
+// -----
+
+func.func @unsupported_type_i4() {
+  // expected-error@+1 {{failed to legalize operation 'memref.alloca'}}
+  %0 = memref.alloca() : memref<4xi4>
+  return
+}