[Bitcode] Avoid duplicating linker option when upgrading

Summary:
The upgrading path from old ModuleFlag based linker options to the new
NamedMetadata based linker option in in materializeMetadata() which gets
called once for the module and once for every GV. The linker options are
getting dup'ed every time and it can create massive amount of the linker
options in the object file that gets created from old bitcode. Fix the
problem by checking if the new option exists or not before upgrade
again.

rdar://64543389

Reviewers: pcc, t.p.northover, dexonsmith, arphaman

Reviewed By: arphaman

Subscribers: hiraditya, jkorous, ributzka, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D83688

(cherry picked from commit ac375c2)

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -2922,12 +2922,15 @@ Error BitcodeReader::materializeMetadata() {
   }
 
   // Upgrade "Linker Options" module flag to "llvm.linker.options" module-level
-  // metadata.
-  if (Metadata *Val = TheModule->getModuleFlag("Linker Options")) {
-    NamedMDNode *LinkerOpts =
-        TheModule->getOrInsertNamedMetadata("llvm.linker.options");
-    for (const MDOperand &MDOptions : cast<MDNode>(Val)->operands())
-      LinkerOpts->addOperand(cast<MDNode>(MDOptions));
+  // metadata. Only upgrade if the new option doesn't exist to avoid upgrade
+  // multiple times.
+  if (!TheModule->getNamedMetadata("llvm.linker.options")) {
+    if (Metadata *Val = TheModule->getModuleFlag("Linker Options")) {
+      NamedMDNode *LinkerOpts =
+          TheModule->getOrInsertNamedMetadata("llvm.linker.options");
+      for (const MDOperand &MDOptions : cast<MDNode>(Val)->operands())
+        LinkerOpts->addOperand(cast<MDNode>(MDOptions));
+    }
   }
 
   DeferredMetadataInfo.clear();

llvm/test/Bitcode/upgrade-linker-options-2.ll

@@ -0,0 +1,12 @@
+;; Test upgrade linker option doesn't create duplicated linker options.
+;; Inputs is generated from IR and checked in as bitcode as it will get rejected by verifier.
+;; define void @test() {
+;;   ret void
+;; }
+;; !llvm.module.flags = !{!0}
+;; !0 = !{i32 6, !"Linker Options", !1}
+;; !1 = !{!2}
+;; !2 = !{!"-framework", !"Foundation"}
+
+; RUN: llvm-dis %S/Inputs/linker-options.bc -o - | FileCheck %s
+; CHECK: !llvm.linker.options = !{!2}