[Arc][SplitFuncs] Ignore extern func ops (#9393)

Author: TaoBi22

lib/Dialect/Arc/Transforms/SplitFuncs.cpp

@@ -47,9 +47,13 @@ struct SplitFuncsPass : public arc::impl::SplitFuncsBase<SplitFuncsPass> {
 
 void SplitFuncsPass::runOnOperation() {
   symbolTable = &getAnalysis<SymbolTable>();
-  for (auto op : llvm::make_early_inc_range(getOperation().getOps<FuncOp>()))
+  for (auto op : llvm::make_early_inc_range(getOperation().getOps<FuncOp>())) {
+    // Ignore extern functions
+    if (op.isExternal())
+      continue;
     if (failed(lowerFunc(op)))
       return signalPassFailure();
+  }
 }
 
 LogicalResult SplitFuncsPass::lowerFunc(FuncOp funcOp) {

test/Dialect/Arc/split-funcs.mlir

@@ -49,3 +49,7 @@ func.func @LongReuse(%arg1: i4, %arg2: i4) -> (i4) {
     %4 = comb.add %0, %1 : i4
     return %4 : i4
 }
+
+// Ignore extern functions
+// CHECK-LABEL: func.func private @extern()
+func.func private @extern()