[DCtoHW] Some modules don't have bodies

Check was segfaulting on `hw.module.extern`s since they don't have
bodies. Extra check was unnecessary since the argument types should
always match the input port types.

Author: teqdruid

lib/Conversion/DCToHW/DCToHW.cpp

@@ -838,10 +838,8 @@ static bool isDCType(Type type) { return isa<TokenType, ValueType>(type); }
 ///  Returns true if the given `op` is considered as legal - i.e. it does not
 ///  contain any dc-typed values.
 static bool isLegalOp(Operation *op) {
-  if (auto funcOp = dyn_cast<HWModuleLike>(op)) {
-    return llvm::none_of(funcOp.getPortTypes(), isDCType) &&
-           llvm::none_of(funcOp.getBodyBlock()->getArgumentTypes(), isDCType);
-  }
+  if (auto funcOp = dyn_cast<HWModuleLike>(op))
+    return llvm::none_of(funcOp.getPortTypes(), isDCType);
 
   bool operandsOK = llvm::none_of(op->getOperandTypes(), isDCType);
   bool resultsOK = llvm::none_of(op->getResultTypes(), isDCType);

test/Conversion/DCToHW/basic.mlir

@@ -196,3 +196,9 @@ hw.module @merge(in %first : !dc.token, in %second : !dc.token, out token : !dc.
     %selected = dc.merge %first, %second
     hw.output %selected : !dc.value<i1>
 }
+
+// CHECK:  hw.module.extern @ext(in %a : i32, out b : i32)
+hw.module.extern @ext(in %a : i32, out b : i32)
+
+// CHECK:  hw.module.extern @extDC(in %a : !esi.channel<i32>, out b : i32)
+hw.module.extern @extDC(in %a : !dc.value<i32>, out b : i32)