[clang] [ORC] Implement basic reoptimization. (PR #67050)

[via cfe-commits]

================
@@ -0,0 +1,179 @@
+//===-- JITLinkRedirectableSymbolManager.cpp - JITLink redirection in Orc -===//
+//
+// 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/ExecutionEngine/Orc/JITLinkRedirectableSymbolManager.h"
+#include "llvm/ExecutionEngine/Orc/Core.h"
+
+#define DEBUG_TYPE "orc"
+
+using namespace llvm;
+using namespace llvm::orc;
+
+void JITLinkRedirectableSymbolManager::emitRedirectableSymbols(
+    std::unique_ptr<MaterializationResponsibility> R,
+    const SymbolAddrMap &InitialDests) {
+  std::unique_lock<std::mutex> Lock(Mutex);
+  if (GetNumAvailableStubs() < InitialDests.size())
+    if (auto Err = grow(InitialDests.size() - GetNumAvailableStubs())) {
+      ES.reportError(std::move(Err));
+      R->failMaterialization();
+      return;
+    }
+
+  JITDylib &TargetJD = R->getTargetJITDylib();
+  SymbolMap NewSymbolDefs;
+  std::vector<SymbolStringPtr> Symbols;
+  for (auto &[K, V] : InitialDests) {
+    StubHandle StubID = AvailableStubs.back();
+    if (SymbolToStubs[&TargetJD].count(K)) {
+      ES.reportError(make_error<StringError>(
+          "Tried to create duplicate redirectable symbols",
+          inconvertibleErrorCode()));
+      R->failMaterialization();
+      return;
+    }
+    dbgs() << *K << "\n";
+    SymbolToStubs[&TargetJD][K] = StubID;
+    NewSymbolDefs[K] = JumpStubs[StubID];
+    NewSymbolDefs[K].setFlags(V.getFlags());
+    Symbols.push_back(K);
+    AvailableStubs.pop_back();
+  }
+
+  if (auto Err = R->replace(absoluteSymbols(NewSymbolDefs))) {
+    ES.reportError(std::move(Err));
+    R->failMaterialization();
+    return;
+  }
+
+  if (auto Err = redirectInner(TargetJD, InitialDests)) {
+    ES.reportError(std::move(Err));
+    R->failMaterialization();
+    return;
+  }
----------------
lhames wrote:

I think the call to `redirectInner` should precede the call to replace: As soon as replace runs anyone waiting on `NewSymbolDefs` will be notified that those symbols are available, but they're not actually usable until the call to `redirectInner`, right?

You should also return the stubs to the pool on all three of the failure paths (or add a FIXME that we should do that in the future).

https://github.com/llvm/llvm-project/pull/67050