diff --git a/llvm/unittests/IR/CMakeLists.txt b/llvm/unittests/IR/CMakeLists.txt
--- a/llvm/unittests/IR/CMakeLists.txt
+++ b/llvm/unittests/IR/CMakeLists.txt
@@ -36,6 +36,7 @@
   PassManagerTest.cpp
   PatternMatch.cpp
   ShuffleVectorInstTest.cpp
+  StructuralHashTest.cpp
   TimePassesTest.cpp
   TypesTest.cpp
   UseTest.cpp
diff --git a/llvm/unittests/IR/StructuralHashTest.cpp b/llvm/unittests/IR/StructuralHashTest.cpp
new file mode 100644
--- /dev/null
+++ b/llvm/unittests/IR/StructuralHashTest.cpp
@@ -0,0 +1,124 @@
+//===- llvm/unittest/IR/StructuralHashTest.cpp ----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/IR/StructuralHash.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/SourceMgr.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+std::unique_ptr<Module> parseIR(LLVMContext &Context, const char *IR) {
+  SMDiagnostic Err;
+  std::unique_ptr<Module> M = parseAssemblyString(IR, Err, Context);
+  if (!M)
+    Err.print("StructuralHashTest", errs());
+  return M;
+}
+
+TEST(StructuralHashTest, Empty) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M1 = parseIR(Ctx, "");
+  std::unique_ptr<Module> M2 = parseIR(Ctx, "");
+  EXPECT_EQ(StructuralHash(*M1), StructuralHash(*M2));
+}
+
+TEST(StructuralHashTest, Basic) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M0 = parseIR(Ctx, "");
+  std::unique_ptr<Module> M1 = parseIR(Ctx, "define void @f() { ret void }");
+  std::unique_ptr<Module> M2 = parseIR(Ctx, "define void @f() { ret void }");
+  std::unique_ptr<Module> M3 = parseIR(Ctx, "@g = global i32 2");
+  std::unique_ptr<Module> M4 = parseIR(Ctx, "@g = global i32 2");
+  EXPECT_NE(StructuralHash(*M0), StructuralHash(*M1));
+  EXPECT_NE(StructuralHash(*M0), StructuralHash(*M3));
+  EXPECT_NE(StructuralHash(*M1), StructuralHash(*M3));
+  EXPECT_EQ(StructuralHash(*M1), StructuralHash(*M2));
+  EXPECT_EQ(StructuralHash(*M3), StructuralHash(*M4));
+}
+
+TEST(StructuralHashTest, BasicFunction) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M = parseIR(Ctx, "define void @f() {\n"
+                                           "  ret void\n"
+                                           "}\n"
+                                           "define void @g() {\n"
+                                           "  ret void\n"
+                                           "}\n"
+                                           "define i32 @h(i32 %i) {\n"
+                                           "  ret i32 %i\n"
+                                           "}\n");
+  EXPECT_EQ(StructuralHash(*M->getFunction("f")),
+            StructuralHash(*M->getFunction("g")));
+  EXPECT_NE(StructuralHash(*M->getFunction("f")),
+            StructuralHash(*M->getFunction("h")));
+}
+
+TEST(StructuralHashTest, Declaration) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M0 = parseIR(Ctx, "");
+  std::unique_ptr<Module> M1 = parseIR(Ctx, "declare void @f()");
+  std::unique_ptr<Module> M2 = parseIR(Ctx, "@g = external global i32");
+  EXPECT_EQ(StructuralHash(*M0), StructuralHash(*M1));
+  EXPECT_EQ(StructuralHash(*M0), StructuralHash(*M2));
+}
+
+TEST(StructuralHashTest, GlobalType) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M1 = parseIR(Ctx, "@g = global i32 1");
+  std::unique_ptr<Module> M2 = parseIR(Ctx, "@g = global float 1.0");
+  EXPECT_NE(StructuralHash(*M1), StructuralHash(*M2));
+}
+
+TEST(StructuralHashTest, Function) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M1 = parseIR(Ctx, "define void @f() { ret void }");
+  std::unique_ptr<Module> M2 = parseIR(Ctx, "define void @f(i32) { ret void }");
+  EXPECT_NE(StructuralHash(*M1), StructuralHash(*M2));
+}
+
+TEST(StructuralHashTest, FunctionRetType) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M1 = parseIR(Ctx, "define void @f() { ret void }");
+  std::unique_ptr<Module> M2 = parseIR(Ctx, "define i32 @f() { ret i32 0 }");
+  // FIXME: should be different
+  EXPECT_EQ(StructuralHash(*M1), StructuralHash(*M2));
+}
+
+TEST(StructuralHashTest, InstructionOpCode) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M1 = parseIR(Ctx, "define void @f(ptr %p) {\n"
+                                            "  %a = load i32, ptr %p\n"
+                                            "  ret void\n"
+                                            "}\n");
+  std::unique_ptr<Module> M2 =
+      parseIR(Ctx, "define void @f(ptr %p) {\n"
+                   "  %a = getelementptr i8, ptr %p, i32 1\n"
+                   "  ret void\n"
+                   "}\n");
+  EXPECT_NE(StructuralHash(*M1), StructuralHash(*M2));
+}
+
+TEST(StructuralHashTest, InstructionType) {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M1 = parseIR(Ctx, "define void @f(ptr %p) {\n"
+                                            "  %a = load i32, ptr %p\n"
+                                            "  ret void\n"
+                                            "}\n");
+  std::unique_ptr<Module> M2 = parseIR(Ctx, "define void @f(ptr %p) {\n"
+                                            "  %a = load i64, ptr %p\n"
+                                            "  ret void\n"
+                                            "}\n");
+  // FIXME: should be different
+  EXPECT_EQ(StructuralHash(*M1), StructuralHash(*M2));
+}
+
+} // end anonymous namespace
diff --git a/llvm/utils/gn/secondary/llvm/unittests/IR/BUILD.gn b/llvm/utils/gn/secondary/llvm/unittests/IR/BUILD.gn
--- a/llvm/utils/gn/secondary/llvm/unittests/IR/BUILD.gn
+++ b/llvm/utils/gn/secondary/llvm/unittests/IR/BUILD.gn
@@ -38,6 +38,7 @@
     "PassBuilderCallbacksTest.cpp",
     "PassManagerTest.cpp",
     "PatternMatch.cpp",
+    "StructuralHashTest.cpp",
     "ShuffleVectorInstTest.cpp",
     "TimePassesTest.cpp",
     "TypesTest.cpp",