Index: lib/IR/Module.cpp
===================================================================
--- lib/IR/Module.cpp
+++ lib/IR/Module.cpp
@@ -494,7 +494,7 @@
 }
 
 void Module::setPICLevel(PICLevel::Level PL) {
-  addModuleFlag(ModFlagBehavior::Error, "PIC Level", PL);
+  addModuleFlag(ModFlagBehavior::Warning, "PIC Level", PL);
 }
 
 PIELevel::Level Module::getPIELevel() const {
Index: lib/Linker/IRMover.cpp
===================================================================
--- lib/Linker/IRMover.cpp
+++ lib/Linker/IRMover.cpp
@@ -1173,6 +1173,26 @@
   return DstTriple.str();
 }
 
+static void mergePICLevel(std::unique_ptr<Module> &SrcM, Module &DstM) {
+  auto *SrcMD = cast_or_null<ConstantAsMetadata>(
+    SrcM->getModuleFlag("PIC Level"));
+  auto *DstMD = cast_or_null<ConstantAsMetadata>(
+    DstM.getModuleFlag("PIC Level"));
+  if (!SrcMD || !DstMD)
+    return;
+  PICLevel::Level SrcL = SrcM->getPICLevel();
+  PICLevel::Level DstL = DstM.getPICLevel();
+  if (SrcL == DstL)
+    return;
+  if (SrcL == PICLevel::Small)
+    return DstM.setPICLevel(PICLevel::Small);
+  if (DstL == PICLevel::Small)
+    return SrcM->setPICLevel(PICLevel::Small);
+  if (SrcL < DstL)
+    return DstM.setPICLevel(SrcL);
+  return SrcM->setPICLevel(DstL);
+}
+
 Error IRLinker::run() {
   // Ensure metadata materialized before value mapping.
   if (SrcM->getMaterializer())
@@ -1245,6 +1265,8 @@
   // are properly remapped.
   linkNamedMDNodes();
 
+  mergePICLevel(SrcM, DstM);
+
   // Merge the module flags into the DstM module.
   return linkModuleFlagsMetadata();
 }
Index: test/Linker/Inputs/module-flags-pic-2-b.ll
===================================================================
--- test/Linker/Inputs/module-flags-pic-2-b.ll
+++ test/Linker/Inputs/module-flags-pic-2-b.ll
@@ -1,3 +1,3 @@
-!0 = !{ i32 1, !"PIC Level", i32 2 }
+!0 = !{ i32 2, !"PIC Level", i32 2 }
 
 !llvm.module.flags = !{!0}
Index: test/Linker/module-flags-pic-1-a.ll
===================================================================
--- test/Linker/module-flags-pic-1-a.ll
+++ test/Linker/module-flags-pic-1-a.ll
@@ -2,8 +2,8 @@
 
 ; test linking modules with specified and default PIC levels
 
-!0 = !{ i32 1, !"PIC Level", i32 1 }
+!0 = !{ i32 2, !"PIC Level", i32 1 }
 
 !llvm.module.flags = !{!0}
 ; CHECK: !llvm.module.flags = !{!0}
-; CHECK: !0 = !{i32 1, !"PIC Level", i32 1}
+; CHECK: !0 = !{i32 2, !"PIC Level", i32 1}
Index: test/Linker/module-flags-pic-2-a.ll
===================================================================
--- test/Linker/module-flags-pic-2-a.ll
+++ test/Linker/module-flags-pic-2-a.ll
@@ -1,10 +1,15 @@
-; RUN: not llvm-link %s %p/Inputs/module-flags-pic-2-b.ll -S -o - 2> %t
-; RUN: FileCheck --check-prefix=CHECK-ERRORS < %t %s
+; RUN: llvm-link %s %p/Inputs/module-flags-pic-2-b.ll -S -o - 2> %t | FileCheck %s \
+; RUN:   --check-prefix=MERGE
+; RUN: FileCheck < %t %s
 
 ; test linking modules with two different PIC levels
 
-!0 = !{ i32 1, !"PIC Level", i32 1 }
+!0 = !{ i32 2, !"PIC Level", i32 1 }
 
 !llvm.module.flags = !{!0}
 
-; CHECK-ERRORS: ERROR: linking module flags 'PIC Level': IDs have conflicting values
+; MERGE: source_filename = "llvm-link"
+; MERGE: !llvm.module.flags = !{!0}
+; MERGE: !0 = !{i32 2, !"PIC Level", i32 1}
+
+; CHECK: WARNING: linking module flags 'PIC Level': IDs have conflicting values