[ORC] Add an output stream operator for SymbolStringPool.

Handy for checking string pool state, e.g. when debugging dangling-pool-entry
errors.

llvm/include/llvm/ExecutionEngine/Orc/DebugUtils.h

@@ -92,6 +92,9 @@ raw_ostream &operator<<(raw_ostream &OS, const SymbolState &S);
 /// Render a LookupKind.
 raw_ostream &operator<<(raw_ostream &OS, const LookupKind &K);
 
+/// Dump a SymbolStringPool. Useful for debugging dangling-pointer crashes.
+raw_ostream &operator<<(raw_ostream &OS, const SymbolStringPool &SSP);
+
 /// A function object that can be used as an ObjectTransformLayer transform
 /// to dump object files to disk at a specified path.
 class DumpObjects {

llvm/include/llvm/ExecutionEngine/Orc/SymbolStringPool.h

@@ -19,6 +19,9 @@
 #include <mutex>
 
 namespace llvm {
+
+class raw_ostream;
+
 namespace orc {
 
 class SymbolStringPtr;
@@ -26,6 +29,10 @@ class SymbolStringPtr;
 /// String pool for symbol names used by the JIT.
 class SymbolStringPool {
   friend class SymbolStringPtr;
+
+  // Implemented in DebugUtils.h.
+  friend raw_ostream &operator<<(raw_ostream &OS, const SymbolStringPool &SSP);
+
 public:
   /// Destroy a SymbolStringPool.
   ~SymbolStringPool();

llvm/lib/ExecutionEngine/Orc/DebugUtils.cpp

@@ -297,6 +297,13 @@ raw_ostream &operator<<(raw_ostream &OS, const SymbolState &S) {
   llvm_unreachable("Invalid state");
 }
 
+raw_ostream &operator<<(raw_ostream &OS, const SymbolStringPool &SSP) {
+  std::lock_guard<std::mutex> Lock(SSP.PoolMutex);
+  for (auto &KV : SSP.Pool)
+    OS << KV.first() << ": " << KV.second << "\n";
+  return OS;
+}
+
 DumpObjects::DumpObjects(std::string DumpDir, std::string IdentifierOverride)
     : DumpDir(std::move(DumpDir)),
       IdentifierOverride(std::move(IdentifierOverride)) {

llvm/unittests/ExecutionEngine/Orc/SymbolStringPoolTest.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ExecutionEngine/Orc/SymbolStringPool.h"
+#include "llvm/ExecutionEngine/Orc/DebugUtils.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
@@ -50,4 +51,15 @@ TEST(SymbolStringPool, ClearDeadEntries) {
   EXPECT_TRUE(SP.empty()) << "pool should be empty";
 }
 
+TEST(SymbolStringPool, DebugDump) {
+  SymbolStringPool SP;
+  auto A1 = SP.intern("a");
+  auto A2 = A1;
+  auto B = SP.intern("b");
+
+  std::string DumpString;
+  raw_string_ostream(DumpString) << SP;
+
+  EXPECT_EQ(DumpString, "a: 2\nb: 1\n");
+}
 }