diff --git a/src/builder/sgir.cpp b/src/builder/sgir.cpp
index c44250d..0ebdf85 100644
--- a/src/builder/sgir.cpp
+++ b/src/builder/sgir.cpp
@@ -9,6 +9,7 @@
 #include <regex>
 #include <tuple>
 #include <numeric>
+#include <string>
 
 #include "mlir/Analysis/Verifier.h"
 #include "mlir/Dialect/StandardOps/Ops.h"
@@ -30,6 +31,29 @@
 namespace onnf {
 namespace {
 
+void replaceAll(
+    std::string& str, const std::string& from, const std::string& to) {
+  if (from.empty())
+    return;
+  size_t start_pos = 0;
+  while ((start_pos = str.find(from, start_pos)) != std::string::npos) {
+    str.replace(start_pos, from.length(), to);
+    start_pos += to.length();  // In case 'to' contains 'from', like replacing
+                               // 'x' with 'yx'
+  }
+}
+
+std::string legalize_name(std::string name) {
+  std::replace(name.begin(), name.end(), '/', '_');
+  std::replace(name.begin(), name.end(), '-', '_');
+  replaceAll(name, ":", "_colon_");
+  // If tensor name starts with a number, prepend n to make it a legal c++
+  // identifier.
+  if (name.size() > 0 && isdigit(name.at(0)))
+    name.insert(0, 1, 'n');
+  return name;
+}
+
 struct OnnxOnnfSymbolMapping {
   /*!
   *  Get MLIR tensor by onnx tensor name.