diff --git a/llvm/lib/CodeGen/MachineModuleInfo.cpp b/llvm/lib/CodeGen/MachineModuleInfo.cpp
--- a/llvm/lib/CodeGen/MachineModuleInfo.cpp
+++ b/llvm/lib/CodeGen/MachineModuleInfo.cpp
@@ -169,6 +169,9 @@
   delete AddrLabelSymbols;
   AddrLabelSymbols = nullptr;
 
+  if (Context.hadError())
+    TheModule->getContext().emitError("MC error");
+
   Context.reset();
   // We don't clear the ExternalContext.
 
diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -30,12 +30,16 @@
 #include "llvm/LTO/LTOBackend.h"
 #include "llvm/LTO/SummaryBasedOptimizations.h"
 #include "llvm/Linker/IRMover.h"
+#include "llvm/MC/MCAsmInfo.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCTargetOptions.h"
 #include "llvm/Object/IRObjectFile.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/Regex.h"
 #include "llvm/Support/SHA1.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetRegistry.h"
@@ -700,6 +704,55 @@
     GO->setComdat(nullptr);
 }
 
+static const char *getTargetAsmSeparator(const Module &M) {
+  std::string Err;
+  const Triple TT(M.getTargetTriple());
+  const Target *T = TargetRegistry::lookupTarget(TT.str(), Err);
+  assert(T && T->hasMCAsmParser());
+
+  MCTargetOptions MCOptions;
+  MCRegisterInfo MRI;
+  std::unique_ptr<MCAsmInfo> MAI(T->createMCAsmInfo(MRI, TT.str(), MCOptions));
+  if (!MAI)
+    return "\\n";
+  return MAI->getSeparatorString();
+}
+
+static void handleModuleInlineAsm(Module &M,
+                                  std::set<StringRef> &NonPrevailingAsmSymbol) {
+  ModuleSymbolTable::CollectAsmSymvers(M, [&](StringRef Name, StringRef Alias) {
+    if (!NonPrevailingAsmSymbol.count(Alias))
+      NonPrevailingAsmSymbol.erase(Name);
+  });
+
+  if (NonPrevailingAsmSymbol.empty())
+    return;
+
+  std::string IA = M.getModuleInlineAsm();
+  std::string Sep = getTargetAsmSeparator(M);
+  std::string PrefixPat = "(^|[[:blank:]]+)";
+  std::string SuffixPat = "($|" + Sep + ")";
+  std::string Symbols = "(" + join(NonPrevailingAsmSymbol, "|") + ")";
+  std::vector<std::string> Pats = {// Remove assignment directive.
+                                   "\\.(set|equ|equiv|eqv)[[:blank:]]+" +
+                                       Symbols + "[[:blank:]]*,[^" + Sep +
+                                       "]+" + SuffixPat,
+                                   // Remove labels.
+                                   Symbols + ":",
+                                   // Remove symbols.
+                                   "\\.(weak|global|globl)[[:blank:]]+" +
+                                       Symbols + "[[:blank:]]*" + SuffixPat};
+  for (auto P : Pats) {
+    Regex RE(PrefixPat + P, Regex::Newline);
+    assert(RE.isValid());
+    IA = RE.sub("", IA);
+  }
+
+  if (std::all_of(IA.begin(), IA.end(), [](auto c) { return std::isspace(c); }))
+    IA = "";
+  M.setModuleInlineAsm(IA);
+}
+
 // Add a regular LTO object to the link.
 // The resulting module needs to be linked into the combined LTO module with
 // linkRegularLTO.
@@ -752,6 +805,7 @@
   Skip();
 
   std::set<const Comdat *> NonPrevailingComdats;
+  std::set<StringRef> NonPrevailingAsmSymbol;
   for (const InputFile::Symbol &Sym : Syms) {
     assert(ResI != ResE);
     SymbolResolution Res = *ResI++;
@@ -798,7 +852,13 @@
           GV->setDLLStorageClass(GlobalValue::DLLStorageClassTypes::
                                  DefaultStorageClass);
       }
-    }
+    } else if (auto *AS = Msym.dyn_cast<ModuleSymbolTable::AsmSymbol *>()) {
+      // Collect non-prevailing symbols.
+      if (!Res.Prevailing)
+        NonPrevailingAsmSymbol.insert(AS->first);
+    } else
+      llvm_unreachable("unknown symbol type");
+
     // Common resolution: collect the maximum size/alignment over all commons.
     // We also record if we see an instance of a common as prevailing, so that
     // if none is prevailing we can ignore it later.
@@ -812,11 +872,15 @@
         CommonRes.Align = max(*SymAlign, CommonRes.Align);
       CommonRes.Prevailing |= Res.Prevailing;
     }
-
   }
+
   if (!M.getComdatSymbolTable().empty())
     for (GlobalValue &GV : M.global_values())
       handleNonPrevailingComdat(GV, NonPrevailingComdats);
+
+  if (!NonPrevailingAsmSymbol.empty())
+    handleModuleInlineAsm(M, NonPrevailingAsmSymbol);
+
   assert(MsymI == MsymE);
   return std::move(Mod);
 }
diff --git a/llvm/test/CodeGen/AMDGPU/lds-initializer.ll b/llvm/test/CodeGen/AMDGPU/lds-initializer.ll
--- a/llvm/test/CodeGen/AMDGPU/lds-initializer.ll
+++ b/llvm/test/CodeGen/AMDGPU/lds-initializer.ll
@@ -1,5 +1,5 @@
-; RUN: llc -march=amdgcn -mcpu=tahiti < %s -o /dev/null 2>&1 | FileCheck %s
-; RUN: llc -march=amdgcn -mcpu=tonga < %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc -march=amdgcn -mcpu=tahiti < %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc -march=amdgcn -mcpu=tonga < %s -o /dev/null 2>&1 | FileCheck %s
 
 ; CHECK: lds: unsupported initializer for address space
 
diff --git a/llvm/test/CodeGen/AMDGPU/lds-zero-initializer.ll b/llvm/test/CodeGen/AMDGPU/lds-zero-initializer.ll
--- a/llvm/test/CodeGen/AMDGPU/lds-zero-initializer.ll
+++ b/llvm/test/CodeGen/AMDGPU/lds-zero-initializer.ll
@@ -1,5 +1,5 @@
-; RUN: llc -march=amdgcn -mcpu=tahiti < %s -o /dev/null 2>&1 | FileCheck %s
-; RUN: llc -march=amdgcn -mcpu=tonga < %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc -march=amdgcn -mcpu=tahiti < %s -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc -march=amdgcn -mcpu=tonga < %s -o /dev/null 2>&1 | FileCheck %s
 
 ; CHECK: lds: unsupported initializer for address space
 
diff --git a/llvm/test/CodeGen/XCore/section-name.ll b/llvm/test/CodeGen/XCore/section-name.ll
--- a/llvm/test/CodeGen/XCore/section-name.ll
+++ b/llvm/test/CodeGen/XCore/section-name.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -march=xcore -o /dev/null 2>&1 | FileCheck %s
+; RUN: not llc < %s -march=xcore -o /dev/null 2>&1 | FileCheck %s
 
 @bar = internal global i32 zeroinitializer
 
diff --git a/llvm/test/LTO/X86/weak-asm.ll b/llvm/test/LTO/X86/weak-asm.ll
new file mode 100644
--- /dev/null
+++ b/llvm/test/LTO/X86/weak-asm.ll
@@ -0,0 +1,48 @@
+; RUN: split-file %s %t
+; RUN: opt %t/t1.ll -o %t1
+; RUN: opt %t/t2.ll -o %t2
+; RUN: opt %t/t3.ll -o %t3
+; RUN: llvm-lto2 run -o %t4 -save-temps %t1 %t2 %t3 \
+; RUN:  -r %t1,foo,px \
+; RUN:  -r %t2,foo, \
+; RUN:  -r %t2,bar,pl \
+; RUN:  -r %t3,foo,
+; RUN: llvm-dis < %t4.0.0.preopt.bc -o - | FileCheck %s --check-prefix=ASM
+; RUN: llvm-nm %t4.0 | FileCheck %s --check-prefix=SYM
+; RUN: llvm-objdump -d --disassemble-symbols=foo %t4.0 \
+; RUN:   | FileCheck %s --check-prefix=DEF
+
+; ASM-NOT: module asm
+
+; SYM: T foo
+
+; DEF: leal    2(%rdi), %eax
+
+;--- t1.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define dso_local i32 @foo(i32 %0) {
+  %2 = add nsw i32 %0, 2
+  ret i32 %2
+}
+
+;--- t2.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+module asm ".weak foo"
+module asm ".equ foo, bar"
+
+@llvm.used = appending global [1 x i8*] [i8* bitcast (i32 (i32)* @bar to i8*)], section "llvm.metadata"
+
+define internal i32 @bar(i32 %0) {
+  %2 = add nsw i32 %0, 1
+  ret i32 %2
+}
+
+;--- t3.ll
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+module asm " .global foo ; foo: "