diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -5364,8 +5364,30 @@
 
       llvm::Value *CalleePtr = Callee.getFunctionPointer();
 
+      // On 32-bit Arm, the low bit of a function pointer indicates whether
+      // it's using the Arm or Thumb instruction set. The actual first
+      // instruction lives at the same address either way, so we must clear
+      // that low bit before using the function address to find the prefix
+      // structure.
+      //
+      // This applies to both Arm and Thumb target triples, because
+      // either one could be used in an interworking context where it
+      // might be passed function pointers of both types.
+      llvm::Value *AlignedCalleePtr;
+      if (CGM.getTriple().isARM() || CGM.getTriple().isThumb()) {
+        llvm::Value *CalleeAddress =
+            Builder.CreatePtrToInt(CalleePtr, IntPtrTy);
+        llvm::Value *Mask = llvm::ConstantInt::get(IntPtrTy, ~1);
+        llvm::Value *AlignedCalleeAddress =
+            Builder.CreateAnd(CalleeAddress, Mask);
+        AlignedCalleePtr =
+            Builder.CreateIntToPtr(AlignedCalleeAddress, CalleePtr->getType());
+      } else {
+        AlignedCalleePtr = CalleePtr;
+      }
+
       llvm::Value *CalleePrefixStruct = Builder.CreateBitCast(
-          CalleePtr, llvm::PointerType::getUnqual(PrefixStructTy));
+          AlignedCalleePtr, llvm::PointerType::getUnqual(PrefixStructTy));
       llvm::Value *CalleeSigPtr =
           Builder.CreateConstGEP2_32(PrefixStructTy, CalleePrefixStruct, -1, 0);
       llvm::Value *CalleeSig =
diff --git a/clang/test/CodeGen/ubsan-function.cpp b/clang/test/CodeGen/ubsan-function.cpp
--- a/clang/test/CodeGen/ubsan-function.cpp
+++ b/clang/test/CodeGen/ubsan-function.cpp
@@ -1,11 +1,15 @@
-// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -o - %s -fsanitize=function -fno-sanitize-recover=all | FileCheck %s
-// RUN: %clang_cc1 -triple aarch64-linux-gnu -emit-llvm -o - %s -fsanitize=function -fno-sanitize-recover=all | FileCheck %s
-// RUN: %clang_cc1 -triple aarch64_be-linux-gnu -emit-llvm -o - %s -fsanitize=function -fno-sanitize-recover=all | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-linux-gnu -emit-llvm -o - %s -fsanitize=function -fno-sanitize-recover=all | FileCheck %s --check-prefixes=CHECK,64
+// RUN: %clang_cc1 -triple aarch64-linux-gnu -emit-llvm -o - %s -fsanitize=function -fno-sanitize-recover=all | FileCheck %s --check-prefixes=CHECK,64
+// RUN: %clang_cc1 -triple aarch64_be-linux-gnu -emit-llvm -o - %s -fsanitize=function -fno-sanitize-recover=all | FileCheck %s --check-prefixes=CHECK,64
+// RUN: %clang_cc1 -triple arm-none-eabi -emit-llvm -o - %s -fsanitize=function -fno-sanitize-recover=all | FileCheck %s --check-prefixes=CHECK,ARM,32
 
 // CHECK: define{{.*}} void @_Z3funv() #0 !func_sanitize ![[FUNCSAN:.*]] {
 void fun() {}
 
 // CHECK-LABEL: define{{.*}} void @_Z6callerPFvvE(ptr noundef %f)
+// ARM:   ptrtoint ptr {{.*}} to i32, !nosanitize !5
+// ARM:   and i32 {{.*}}, -2, !nosanitize !5
+// ARM:   inttoptr i32 {{.*}} to ptr, !nosanitize !5
 // CHECK: getelementptr <{ i32, i32 }>, ptr {{.*}}, i32 -1, i32 0, !nosanitize
 // CHECK: load i32, ptr {{.*}}, align {{.*}}, !nosanitize
 // CHECK: icmp eq i32 {{.*}}, -1056584962, !nosanitize
@@ -16,7 +20,8 @@
 // CHECK: icmp eq i32 {{.*}}, -1522505972, !nosanitize
 // CHECK: br i1 {{.*}}, label %[[LABEL3:.*]], label %[[LABEL2:[^,]*]], {{.*}}!nosanitize
 // CHECK: [[LABEL2]]:
-// CHECK: call void @__ubsan_handle_function_type_mismatch_abort(ptr @[[#]], i64 %[[#]]) #[[#]], !nosanitize
+// 64:    call void @__ubsan_handle_function_type_mismatch_abort(ptr @[[#]], i64 %[[#]]) #[[#]], !nosanitize
+// 32:    call void @__ubsan_handle_function_type_mismatch_abort(ptr @[[#]], i32 %[[#]]) #[[#]], !nosanitize
 // CHECK-NEXT: unreachable, !nosanitize
 // CHECK-EMPTY:
 // CHECK-NEXT: [[LABEL3]]: