[PATCH] D71219: Fix conflict value for metadata "Objective-C Garbage Collection" in the mix of swift and Objective-C bitcode

[Jin Lin via Phabricator via llvm-commits]

jinlin created this revision.
jinlin added a reviewer: rjmccall.
Herald added subscribers: llvm-commits, dexonsmith, hiraditya, mehdi_amini.
Herald added a project: LLVM.

The change is to fix conflict value for metadata "Objective-C Garbage Collection" in the mix of swift and Objective-C bitcode.
The purpose is to provide the support of LTO for swift and Objective-C mixed project.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71219

Files:
  llvm/lib/Linker/IRMover.cpp


Index: llvm/lib/Linker/IRMover.cpp
===================================================================
--- llvm/lib/Linker/IRMover.cpp
+++ llvm/lib/Linker/IRMover.cpp
@@ -1260,15 +1260,52 @@
       Flags[ID].first = SrcOp;
     };
 
+    // Check the input bitcode is swift generated bitcode.
+    auto isSwiftBitCode = [&](Module &M) {
+      SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
+      M.getModuleFlagsMetadata(ModuleFlags);
+      for (const auto &MFE: ModuleFlags) {
+        if (MFE.Behavior == Module::Require)
+          continue;
+        StringRef Key = MFE.Key->getString();
+        if (Key == "Swift Version")
+          return true;
+      }
+      return false;
+    };
+
     // If either flag has override behavior, handle it first.
     if (DstBehaviorValue == Module::Override) {
       // Diagnose inconsistent flags which both have override behavior.
       if (SrcBehaviorValue == Module::Override &&
-          SrcOp->getOperand(2) != DstOp->getOperand(2))
+          SrcOp->getOperand(2) != DstOp->getOperand(2)) {
+        if (ID->getString().equals("Objective-C Garbage Collection")) {
+
+          // Merge the value of metadata "Objective-C Garbage Collection"
+          // into one value by shifting. The purpose of this change is
+          // to support LTO in Swift and Objective-C mixed project.
+
+          auto Int32Ty = Type::getInt32Ty(DstM.getContext());
+          auto SrcMD = dyn_cast<ConstantAsMetadata>(SrcOp->getOperand(2));
+          auto DstMD = dyn_cast<ConstantAsMetadata>(DstOp->getOperand(2));
+          assert(!SrcMD && !DstMD);
+          unsigned SrcVal = SrcMD->getValue()->getUniqueInteger().getZExtValue();
+          unsigned DstVal = DstMD->getValue()->getUniqueInteger().getZExtValue();
+          if ((isSwiftBitCode(*SrcM) && DstVal < 64) ||
+              (isSwiftBitCode(DstM) && SrcVal < 64)) {
+            unsigned resVal = SrcVal | DstVal;
+            SrcOp->replaceOperandWith(2,
+              ConstantAsMetadata::get(ConstantInt::get(Int32Ty,resVal)));
+            DstOp->replaceOperandWith(2,
+              ConstantAsMetadata::get(ConstantInt::get(Int32Ty,resVal)));
+            continue;
+          }
+        }
         return stringErr("linking module flags '" + ID->getString() +
                          "': IDs have conflicting override values in '" +
                          SrcM->getModuleIdentifier() + "' and '" +
                          DstM.getModuleIdentifier() + "'");
+      }
       continue;
     } else if (SrcBehaviorValue == Module::Override) {
       // Update the destination flag to that of the source.


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