Index: llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
===================================================================
--- llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
+++ llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
@@ -16,6 +16,7 @@
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/EquivalenceClasses.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/ADT/Triple.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
@@ -115,6 +116,11 @@
   // linker knows about the symbol; this pass replaces the function body.
   F->deleteBody();
   F->setAlignment(4096);
+
+  Triple T(M.getTargetTriple());
+  if (T.isARM() || T.isThumb())
+    F->addFnAttr("target-features", "+thumb-mode");
+
   auto args = F->arg_begin();
   Value &CallSiteTypeId = *(args++);
   CallSiteTypeId.setName("CallSiteTypeId");
Index: llvm/test/Transforms/CrossDSOCFI/thumb.ll
===================================================================
--- /dev/null
+++ llvm/test/Transforms/CrossDSOCFI/thumb.ll
@@ -0,0 +1,22 @@
+; RUN: opt -mtriple=armv7-linux-android -S -cross-dso-cfi < %s | FileCheck --check-prefix=THUMB %s
+; RUN: opt -mtriple=thumbv7-linux-android -S -cross-dso-cfi < %s | FileCheck --check-prefix=THUMB %s
+; RUN: opt -mtriple=i386-linux -S -cross-dso-cfi < %s | FileCheck --check-prefix=NOTHUMB %s
+; RUN: opt -mtriple=x86_64-linux -S -cross-dso-cfi < %s | FileCheck --check-prefix=NOTHUMB %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+
+define signext i8 @f() !type !0 !type !1 {
+entry:
+  ret i8 1
+}
+
+!llvm.module.flags = !{!2}
+
+!0 = !{i64 0, !"_ZTSFcvE"}
+!1 = !{i64 0, i64 111}
+!2 = !{i32 4, !"Cross-DSO CFI", i32 1}
+
+; THUMB: define void @__cfi_check({{.*}} #[[A:.*]] align 4096
+; THUMB: attributes #[[A]] = { {{.*}}"target-features"="+thumb-mode"
+
+; NOTHUMB: define void @__cfi_check({{.*}} align 4096