Index: llvm/trunk/lib/Transforms/IPO/LowerTypeTests.cpp
===================================================================
--- llvm/trunk/lib/Transforms/IPO/LowerTypeTests.cpp
+++ llvm/trunk/lib/Transforms/IPO/LowerTypeTests.cpp
@@ -329,6 +329,7 @@
   unsigned getJumpTableEntrySize();
   Type *getJumpTableEntryType();
   void createJumpTableEntry(raw_ostream &AsmOS, raw_ostream &ConstraintOS,
+                            Triple::ArchType JumpTableArch,
                             SmallVectorImpl<Value *> &AsmArgs, Function *Dest);
   void verifyTypeMDNode(GlobalObject *GO, MDNode *Type);
   void buildBitSetsFromFunctions(ArrayRef<Metadata *> TypeIds,
@@ -983,15 +984,16 @@
 // constraints and arguments to AsmOS, ConstraintOS and AsmArgs.
 void LowerTypeTestsModule::createJumpTableEntry(
     raw_ostream &AsmOS, raw_ostream &ConstraintOS,
-    SmallVectorImpl<Value *> &AsmArgs, Function *Dest) {
+    Triple::ArchType JumpTableArch, SmallVectorImpl<Value *> &AsmArgs,
+    Function *Dest) {
   unsigned ArgIndex = AsmArgs.size();
 
-  if (Arch == Triple::x86 || Arch == Triple::x86_64) {
+  if (JumpTableArch == Triple::x86 || JumpTableArch == Triple::x86_64) {
     AsmOS << "jmp ${" << ArgIndex << ":c}@plt\n";
     AsmOS << "int3\nint3\nint3\n";
-  } else if (Arch == Triple::arm || Arch == Triple::aarch64) {
+  } else if (JumpTableArch == Triple::arm || JumpTableArch == Triple::aarch64) {
     AsmOS << "b $" << ArgIndex << "\n";
-  } else if (Arch == Triple::thumb) {
+  } else if (JumpTableArch == Triple::thumb) {
     AsmOS << "b.w $" << ArgIndex << "\n";
   } else {
     report_fatal_error("Unsupported architecture for jump tables");
@@ -1078,6 +1080,46 @@
   PlaceholderFn->eraseFromParent();
 }
 
+static bool isThumbFunction(Function *F, Triple::ArchType ModuleArch) {
+  Attribute TFAttr = F->getFnAttribute("target-features");
+  if (!TFAttr.hasAttribute(Attribute::None)) {
+    SmallVector<StringRef, 6> Features;
+    TFAttr.getValueAsString().split(Features, ',');
+    for (StringRef Feature : Features) {
+      if (Feature == "-thumb-mode")
+        return false;
+      else if (Feature == "+thumb-mode")
+        return true;
+    }
+  }
+
+  return ModuleArch == Triple::thumb;
+}
+
+// Each jump table must be either ARM or Thumb as a whole for the bit-test math
+// to work. Pick one that matches the majority of members to minimize interop
+// veneers inserted by the linker.
+static Triple::ArchType
+selectJumpTableArmEncoding(ArrayRef<GlobalTypeMember *> Functions,
+                           Triple::ArchType ModuleArch) {
+  if (ModuleArch != Triple::arm && ModuleArch != Triple::thumb)
+    return ModuleArch;
+
+  unsigned ArmCount = 0, ThumbCount = 0;
+  for (const auto GTM : Functions) {
+    if (!GTM->isDefinition()) {
+      // PLT stubs are always ARM.
+      ++ArmCount;
+      continue;
+    }
+
+    Function *F = cast<Function>(GTM->getGlobal());
+    ++(isThumbFunction(F, ModuleArch) ? ThumbCount : ArmCount);
+  }
+
+  return ArmCount > ThumbCount ? Triple::arm : Triple::thumb;
+}
+
 void LowerTypeTestsModule::createJumpTable(
     Function *F, ArrayRef<GlobalTypeMember *> Functions) {
   std::string AsmStr, ConstraintStr;
@@ -1085,8 +1127,10 @@
   SmallVector<Value *, 16> AsmArgs;
   AsmArgs.reserve(Functions.size() * 2);
 
+  Triple::ArchType JumpTableArch = selectJumpTableArmEncoding(Functions, Arch);
+
   for (unsigned I = 0; I != Functions.size(); ++I)
-    createJumpTableEntry(AsmOS, ConstraintOS, AsmArgs,
+    createJumpTableEntry(AsmOS, ConstraintOS, JumpTableArch, AsmArgs,
                          cast<Function>(Functions[I]->getGlobal()));
 
   // Try to emit the jump table at the end of the text segment.
@@ -1103,10 +1147,14 @@
   // attribute.
   if (OS != Triple::Win32)
     F->addFnAttr(llvm::Attribute::Naked);
-  // Thumb jump table assembly needs Thumb2. The following attribute is added by
-  // Clang for -march=armv7.
-  if (Arch == Triple::thumb)
+  if (JumpTableArch == Triple::arm)
+    F->addFnAttr("target-features", "-thumb-mode");
+  if (JumpTableArch == Triple::thumb) {
+    F->addFnAttr("target-features", "+thumb-mode");
+    // Thumb jump table assembly needs Thumb2. The following attribute is added
+    // by Clang for -march=armv7.
     F->addFnAttr("target-cpu", "cortex-a8");
+  }
 
   BasicBlock *BB = BasicBlock::Create(M.getContext(), "entry", F);
   IRBuilder<> IRB(BB);
Index: llvm/trunk/test/Transforms/LowerTypeTests/function-arm-thumb.ll
===================================================================
--- llvm/trunk/test/Transforms/LowerTypeTests/function-arm-thumb.ll
+++ llvm/trunk/test/Transforms/LowerTypeTests/function-arm-thumb.ll
@@ -0,0 +1,41 @@
+; RUN: opt -S -mtriple=arm-unknown-linux-gnu -lowertypetests -lowertypetests-summary-action=export -lowertypetests-read-summary=%S/Inputs/use-typeid1-typeid2.yaml -lowertypetests-write-summary=%t < %s | FileCheck %s
+
+target datalayout = "e-p:64:64"
+
+define void @f1() "target-features"="+thumb-mode" !type !0 {
+  ret void
+}
+
+define void @g1() "target-features"="-thumb-mode" !type !0 {
+  ret void
+}
+
+define void @f2() "target-features"="+thumb-mode" !type !1 {
+  ret void
+}
+
+define void @g2() "target-features"="-thumb-mode" !type !1 {
+  ret void
+}
+
+define void @h2() "target-features"="-thumb-mode" !type !1 {
+  ret void
+}
+
+!0 = !{i32 0, !"typeid1"}
+!1 = !{i32 0, !"typeid2"}
+
+; CHECK: define private void {{.*}} #[[AT:.*]] section ".text.cfi" align 4 {
+; CHECK-NEXT: entry:
+; CHECK-NEXT:  call void asm sideeffect "b.w $0\0Ab.w $1\0A", "s,s"(void ()* @f1.cfi, void ()* @g1.cfi)
+; CHECK-NEXT:  unreachable
+; CHECK-NEXT: }
+
+; CHECK: define private void {{.*}} #[[AA:.*]] section ".text.cfi" align 4 {
+; CHECK-NEXT: entry:
+; CHECK-NEXT:  call void asm sideeffect "b $0\0Ab $1\0Ab $2\0A", "s,s,s"(void ()* @f2.cfi, void ()* @g2.cfi, void ()* @h2.cfi)
+; CHECK-NEXT:  unreachable
+; CHECK-NEXT: }
+
+; CHECK-DAG: attributes #[[AA]] = { naked "target-features"="-thumb-mode" }
+; CHECK-DAG: attributes #[[AT]] = { naked "target-cpu"="cortex-a8" "target-features"="+thumb-mode" }