Index: clang/lib/CodeGen/CGExpr.cpp
===================================================================
--- clang/lib/CodeGen/CGExpr.cpp
+++ clang/lib/CodeGen/CGExpr.cpp
@@ -2928,6 +2928,18 @@
   llvm::CallInst::Create(
       llvm::Intrinsic::getDeclaration(M, llvm::Intrinsic::trap), "", BB);
   llvm::ReturnInst::Create(Ctx, nullptr, BB);
+
+  // Set default function attributes, but force thumb encoding if applicable.
+  const CGFunctionInfo &FI =
+      CGM.getTypes().arrangeBuiltinFunctionDeclaration(getContext().VoidTy, {});
+  FunctionDecl *FD =
+      FunctionDecl::Create(getContext(), getContext().getTranslationUnitDecl(),
+                           {}, {}, {}, getContext().VoidTy, nullptr, SC_Extern);
+  const auto &Triple = getTarget().getTriple();
+  if (Triple.isARM() || Triple.isThumb()) {
+    FD->addAttr(TargetAttr::CreateImplicit(getContext(), "thumb"));
+  }
+  CGM.SetLLVMFunctionAttributes(FD, FI, F);
 }
 
 // This function is basically a switch over the CFI failure kind, which is
@@ -3011,6 +3023,9 @@
   }
 
   FinishFunction();
+
+  CGM.SetLLVMFunctionAttributes(nullptr, FI, F);
+
   // The only reference to this function will be created during LTO link.
   // Make sure it survives until then.
   CGM.addUsedGlobal(F);
Index: clang/test/CodeGen/cfi-check-thumb.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/cfi-check-thumb.c
@@ -0,0 +1,18 @@
+// Test that __cfi_check and __cfi_check_fail have common attributes and calling convention.
+// Also __cfi_check is always using Thumb encoding.
+// RUN: %clang_cc1 -triple armv7-linux-android -O0 -fsanitize-cfi-cross-dso \
+// RUN:     -fsanitize=cfi-vcall \
+// RUN:     -emit-llvm -o - %s | FileCheck --check-prefixes=CHECK,CHECK-ARM %s
+//
+// RUN: %clang_cc1 -triple thumbv7-linux-android -O0 -fsanitize-cfi-cross-dso \
+// RUN:     -fsanitize=cfi-vcall \
+// RUN:     -emit-llvm -o - %s | FileCheck --check-prefixes=CHECK,CHECK-THUMB %s
+//
+// REQUIRES: arm-registered-target
+
+// CHECK-ARM: define weak_odr hidden void @__cfi_check_fail(i8*, i8*) #[[ARM:.*]] {
+// CHECK-THUMB: define weak_odr hidden void @__cfi_check_fail(i8*, i8*) #[[THUMB:.*]] {
+// CHECK: define weak void @__cfi_check(i64, i8*, i8*) #[[THUMB:.*]] {
+
+// CHECK-ARM: attributes #[[ARM]] = {{.*}}"target-features"="{{.*}}-thumb-mode
+// CHECK: attributes #[[THUMB]] = {{.*}}"target-features"="{{.*}}+thumb-mode
Index: llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
===================================================================
--- llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
+++ llvm/lib/Transforms/IPO/CrossDSOCFI.cpp
@@ -117,10 +117,6 @@
   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
===================================================================
--- llvm/test/Transforms/CrossDSOCFI/thumb.ll
+++ /dev/null
@@ -1,22 +0,0 @@
-; 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