[FIRRTL] Intrinsics: Add checkAndConvert, anchor vtable.

include/circt/Dialect/FIRRTL/FIRRTLIntrinsics.h

@@ -188,18 +188,44 @@ struct GenericIntrinsic {
 ///
 /// Intrinsic converters contain validation logic, along with a converter
 /// method to transform generic intrinsic ops to their implementation.
+
+/// Instances of a converter must be stateless and are expected to be able
+/// to be used simultaneously on different intrinsic operations in parallel.
 class IntrinsicConverter {
 public:
+  virtual void anchor(); // vtable anchor
+
   virtual ~IntrinsicConverter() = default;
 
   /// Checks whether the intrinsic is well-formed.
   ///
   /// This or's multiple ParseResults together, returning true on failure.
-  virtual bool check(GenericIntrinsic gi) = 0;
+  virtual bool check(GenericIntrinsic gi) {
+    llvm::report_fatal_error(
+        "check() or checkAndConvert() must be implemented");
+    return true;
+  }
 
   /// Transform the intrinsic to its implementation.
   virtual void convert(GenericIntrinsic gi, GenericIntrinsicOpAdaptor adaptor,
-                       PatternRewriter &rewriter) = 0;
+                       PatternRewriter &rewriter) {
+    llvm::report_fatal_error(
+        "convert() or checkAndConvert() must be implemented");
+  }
+
+  /// Perform both check and convert, defaults to using check() and convert().
+  /// Return failure if check fails (no changes to IR should be made).
+  /// Otherwise, transform the intrinsic and return success.
+  /// Prefer overriding check and convert, but overriding this can avoid
+  /// recomputing work done during check needed for the conversion.
+  virtual LogicalResult checkAndConvert(GenericIntrinsic gi,
+                                        GenericIntrinsicOpAdaptor adaptor,
+                                        PatternRewriter &rewriter) {
+    if (check(gi))
+      return failure();
+    convert(gi, adaptor, rewriter);
+    return success();
+  };
 };
 
 template <typename OpTy>

lib/Dialect/FIRRTL/FIRRTLIntrinsics.cpp

@@ -14,6 +14,9 @@
 using namespace circt;
 using namespace firrtl;
 
+// vtable anchor
+void IntrinsicConverter::anchor() {}
+
 //===----------------------------------------------------------------------===//
 // GenericIntrinsic
 //===----------------------------------------------------------------------===//
@@ -126,11 +129,10 @@ class IntrinsicOpConversion final
     }
 
     auto &conv = *it->second;
-    if (conv.check(GenericIntrinsic(op)))
-      return failure();
-    conv.convert(GenericIntrinsic(op), adaptor, rewriter);
-    ++numConversions;
-    return success();
+    auto result = conv.checkAndConvert(GenericIntrinsic(op), adaptor, rewriter);
+    if (succeeded(result))
+      ++numConversions;
+    return result;
   }
 
 private: