Index: llvm/lib/Transforms/Utils/ModuleUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/ModuleUtils.cpp
+++ llvm/lib/Transforms/Utils/ModuleUtils.cpp
@@ -209,13 +209,44 @@
   bool ExportsSymbols = false;
   auto AddGlobal = [&](GlobalValue &GV) {
     if (GV.isDeclaration() || GV.getName().startswith("llvm.") ||
-        !GV.hasExternalLinkage() || GV.hasComdat())
+        (!GV.hasExternalLinkage() &&
+          !(GV.hasWeakLinkage() || GV.hasWeakAnyLinkage() ||
+            GV.hasWeakODRLinkage() || GV.hasLinkOnceLinkage() ||
+            GV.hasLinkOnceODRLinkage() || GV.hasCommonLinkage() ||
+            GV.hasComdat())) ||
+        GV.hasComdat())
       return;
     ExportsSymbols = true;
     Md5.update(GV.getName());
     Md5.update(ArrayRef<uint8_t>{0});
   };
 
+  if (auto *Used = M->getNamedGlobal("llvm.used")) {
+    if (const auto *A = dyn_cast<ConstantArray>(Used->getInitializer())) {
+      for (const Value *Op : A->operands()) {
+        if (const auto *GV = dyn_cast<GlobalValue>(Op->stripPointerCasts())) {
+          Md5.update(GV->getName());
+          Md5.update(ArrayRef<uint8_t>{0});
+        }
+      }
+    }
+  }
+  if (auto *Used = M->getNamedGlobal("llvm.global_ctors")) {
+    if (const auto *A = dyn_cast<ConstantArray>(Used->getInitializer())) {
+      for (const Value *Op : A->operands()) {
+        if (const auto *GV = dyn_cast<ConstantStruct>(Op)) {
+          auto *Elt = GV->getAggregateElement(1);
+          Md5.update(Elt->getName());
+          Md5.update(ArrayRef<uint8_t>{0});
+        }
+      }
+    }
+  }
+
+  Md5.update(M->getModuleIdentifier());
+  Md5.update(ArrayRef<uint8_t>{0});
+  ExportsSymbols = true;
+
   for (auto &F : *M)
     AddGlobal(F);
   for (auto &GV : M->globals())
@@ -233,6 +264,9 @@
 
   SmallString<32> Str;
   MD5::stringifyResult(R, Str);
+
+  LLVM_DEBUG(dbgs() << "Generated ModuleID: " << Str.str() << "\n");
+
   return ("." + Str).str();
 }
 
Index: llvm/test/LTO/Resolution/X86/llvm-used-moduleid.ll
===================================================================
--- /dev/null
+++ llvm/test/LTO/Resolution/X86/llvm-used-moduleid.ll
@@ -0,0 +1,19 @@
+; RUN: opt <%s -thinlto-bc -thinlto-split-lto-unit -o %t0
+; RUN: llvm-bcanalyzer %t0 | FileCheck %s
+
+target triple="x86_64-pc-linux-gnu"
+
+@llvm.used = appending global [1 x i8*] [i8* bitcast (void ()* @a to i8*)], !type !0
+
+declare i1 @llvm.type.test(i8*, metadata)
+declare void @llvm.assume(i1)
+
+; CHECK: GLOBALVAL_SUMMARY_BLOCK
+; CHECK: FULL_LTO_GLOBALVAL_SUMMARY_BLOCK
+define internal void @a() {
+  %1 = call i1 @llvm.type.test(i8* undef, metadata !"a")
+  call void @llvm.assume(i1 %1)
+  ret void
+}
+
+!0 = !{i64 16, !"a"}
Index: llvm/test/LTO/Resolution/X86/weak-linkage-moduleid.ll
===================================================================
--- /dev/null
+++ llvm/test/LTO/Resolution/X86/weak-linkage-moduleid.ll
@@ -0,0 +1,19 @@
+; RUN: opt <%s -thinlto-bc -thinlto-split-lto-unit -o %t0
+; RUN: llvm-bcanalyzer %t0 | FileCheck %s
+
+target triple="x86_64-pc-linux-gnu"
+
+@p = weak global void ()* @a, !type !0
+
+declare i1 @llvm.type.test(i8*, metadata)
+declare void @llvm.assume(i1)
+
+; CHECK: GLOBALVAL_SUMMARY_BLOCK
+; CHECK: FULL_LTO_GLOBALVAL_SUMMARY_BLOCK
+define internal void @a() {
+  %1 = call i1 @llvm.type.test(i8* undef, metadata !"a")
+  call void @llvm.assume(i1 %1)
+  ret void
+}
+
+!0 = !{i64 16, !"a"}
Index: llvm/test/LTO/X86/path-moduleid.ll
===================================================================
--- /dev/null
+++ llvm/test/LTO/X86/path-moduleid.ll
@@ -0,0 +1,27 @@
+; REQUIRES: asserts
+; Test that chaning the path to the module doesn't effect the ModuleID. This
+; file and Inputs/path-moduleid.ll have the same content, and thus should have
+; the same ModuleID.
+; RUN: opt -o /dev/null -thinlto-bc -thinlto-split-lto-unit=1 --debug-only=moduleutils %s 2>%t0
+; RUN: mkdir -p %t; cp %s %t/path-moduleid.ll
+; RUN: opt -o /dev/null -thinlto-bc -thinlto-split-lto-unit=1 --debug-only=moduleutils %t/path-moduleid.ll 2>%t1
+; RUN: FileCheck %s <%t0
+; RUN: FileCheck %s <%t1
+; RUN: not diff %t0 %t1
+
+; CHECK: Generated ModuleID:
+target triple="x86_64-pc-linux-gnu"
+
+@llvm.used = appending global [1 x i8*] [i8* bitcast (void ()* @a to i8*)], !type !0
+
+declare i1 @llvm.type.test(i8*, metadata)
+declare void @llvm.assume(i1)
+
+define internal void @a() {
+  %1 = call i1 @llvm.type.test(i8* undef, metadata !"a")
+  call void @llvm.assume(i1 %1)
+  ret void
+}
+
+
+!0 = !{i64 16, !"a"}
Index: llvm/test/Transforms/Util/generate-moduleid.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/Util/generate-moduleid.ll
@@ -0,0 +1,17 @@
+; REQUIRES: asserts
+; RUN: opt --thinlto-split-lto-unit=1 --thinlto-bc -o %t0 -debug-only=moduleutils <%s 2>&1 | FileCheck %s
+; CHECK: Generated ModuleID
+
+target triple="x86_64-pc-linux-gnu"
+
+declare i1 @llvm.type.test(i8*, metadata)
+
+define internal void @foo() !type !1{
+entry:
+  %0 = tail call i1 @llvm.type.test(i8* null, metadata !"")
+  ret void
+}
+
+@llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 103, void ()* @foo, i8* null }]
+
+!1 = !{i64 0, !"foo"}