diff --git a/clang/include/clang/Basic/CodeGenOptions.def b/clang/include/clang/Basic/CodeGenOptions.def
--- a/clang/include/clang/Basic/CodeGenOptions.def
+++ b/clang/include/clang/Basic/CodeGenOptions.def
@@ -388,6 +388,9 @@
 /// Whether to emit unused static constants.
 CODEGENOPT(KeepStaticConsts, 1, 0)
 
+/// Whether to not follow the AAPCS that enforce at least one read before storing to a volatile bitfield
+CODEGENOPT(ForceAAPCSBitfieldLoad, 1, 0)
+
 #undef CODEGENOPT
 #undef ENUM_CODEGENOPT
 #undef VALUE_CODEGENOPT
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -2317,6 +2317,9 @@
 def mcmse : Flag<["-"], "mcmse">, Group<m_arm_Features_Group>,
   Flags<[DriverOption,CC1Option]>,
   HelpText<"Allow use of CMSE (Armv8-M Security Extensions)">;
+def ForceAAPCSBitfieldLoad : Flag<["-"], "fAAPCSBitfieldLoad">, Group<m_arm_Features_Group>,
+  Flags<[DriverOption,CC1Option]>,
+  HelpText<"Follows the AAPCS standard that all volatile bit-field write generates at least one load. (ARM only).">;
 
 def mgeneral_regs_only : Flag<["-"], "mgeneral-regs-only">, Group<m_aarch64_Features_Group>,
   HelpText<"Generate code which only uses the general purpose registers (AArch64 only)">;
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
@@ -2080,6 +2080,14 @@
     SrcVal = Builder.CreateOr(Val, SrcVal, "bf.set");
   } else {
     assert(Offset == 0);
+    // Acording to the AACPS:
+    // When a volatile bit-field is written, and its container does not overlap
+    // with any non-bit-field member, its container must be read exactly once and
+    // written exactly once using the access width appropriate to the type of the
+    // container. The two accesses are not atomic.
+    if (Dst.isVolatileQualified() && isAAPCS(CGM.getTarget()) &&
+        CGM.getCodeGenOpts().ForceAAPCSBitfieldLoad)
+      Builder.CreateLoad(Ptr, true, "bf.load");
   }
 
   // Write the new value back out.
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -1442,6 +1442,7 @@
   Opts.SymbolPartition =
       std::string(Args.getLastArgValue(OPT_fsymbol_partition_EQ));
 
+  Opts.ForceAAPCSBitfieldLoad = Args.hasArg(OPT_ForceAAPCSBitfieldLoad);
   return Success;
 }
 
diff --git a/clang/test/CodeGen/aapcs-bitfield.c b/clang/test/CodeGen/aapcs-bitfield.c
--- a/clang/test/CodeGen/aapcs-bitfield.c
+++ b/clang/test/CodeGen/aapcs-bitfield.c
@@ -1,6 +1,8 @@
 // NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
 // RUN: %clang_cc1 -triple armv8-none-linux-eabi %s -emit-llvm -o - -O3 | FileCheck %s -check-prefix=LE
 // RUN: %clang_cc1 -triple armebv8-none-linux-eabi %s -emit-llvm -o - -O3 | FileCheck %s -check-prefix=BE
+// RUN: %clang_cc1 -triple armv8-none-linux-eabi %s -emit-llvm -o - -O3 -fAAPCSBitfieldLoad | FileCheck %s -check-prefixes=LE,LENUMLOADS
+// RUN: %clang_cc1 -triple armebv8-none-linux-eabi %s -emit-llvm -o - -O3 -fAAPCSBitfieldLoad | FileCheck %s -check-prefixes=BE,BENUMLOADS
 
 struct st0 {
   short c : 7;
@@ -680,12 +682,14 @@
 // LE-LABEL: @store_st11(
 // LE-NEXT:  entry:
 // LE-NEXT:    [[F:%.*]] = getelementptr inbounds [[STRUCT_ST11:%.*]], %struct.st11* [[M:%.*]], i32 0, i32 1
+// LENUMLOADS-NEXT:    [[BF_LOAD:%.*]] = load volatile i16, i16* [[F]], align 1
 // LE-NEXT:    store volatile i16 1, i16* [[F]], align 1
 // LE-NEXT:    ret void
 //
 // BE-LABEL: @store_st11(
 // BE-NEXT:  entry:
 // BE-NEXT:    [[F:%.*]] = getelementptr inbounds [[STRUCT_ST11:%.*]], %struct.st11* [[M:%.*]], i32 0, i32 1
+// BENUMLOADS-NEXT:    [[BF_LOAD:%.*]] = load volatile i16, i16* [[F]], align 1
 // BE-NEXT:    store volatile i16 1, i16* [[F]], align 1
 // BE-NEXT:    ret void
 //
@@ -698,6 +702,7 @@
 // LE-NEXT:    [[F:%.*]] = getelementptr inbounds [[STRUCT_ST11:%.*]], %struct.st11* [[M:%.*]], i32 0, i32 1
 // LE-NEXT:    [[BF_LOAD:%.*]] = load volatile i16, i16* [[F]], align 1
 // LE-NEXT:    [[INC:%.*]] = add i16 [[BF_LOAD]], 1
+// LENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i16, i16* [[F]], align 1
 // LE-NEXT:    store volatile i16 [[INC]], i16* [[F]], align 1
 // LE-NEXT:    ret void
 //
@@ -706,6 +711,7 @@
 // BE-NEXT:    [[F:%.*]] = getelementptr inbounds [[STRUCT_ST11:%.*]], %struct.st11* [[M:%.*]], i32 0, i32 1
 // BE-NEXT:    [[BF_LOAD:%.*]] = load volatile i16, i16* [[F]], align 1
 // BE-NEXT:    [[INC:%.*]] = add i16 [[BF_LOAD]], 1
+// BENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i16, i16* [[F]], align 1
 // BE-NEXT:    store volatile i16 [[INC]], i16* [[F]], align 1
 // BE-NEXT:    ret void
 //
@@ -882,6 +888,7 @@
 // LE-NEXT:    [[TMP0:%.*]] = getelementptr [[STRUCT_ST14:%.*]], %struct.st14* [[S:%.*]], i32 0, i32 0
 // LE-NEXT:    [[BF_LOAD:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // LE-NEXT:    [[INC:%.*]] = add i8 [[BF_LOAD]], 1
+// LENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // LE-NEXT:    store volatile i8 [[INC]], i8* [[TMP0]], align 1
 // LE-NEXT:    ret void
 //
@@ -890,6 +897,7 @@
 // BE-NEXT:    [[TMP0:%.*]] = getelementptr [[STRUCT_ST14:%.*]], %struct.st14* [[S:%.*]], i32 0, i32 0
 // BE-NEXT:    [[BF_LOAD:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // BE-NEXT:    [[INC:%.*]] = add i8 [[BF_LOAD]], 1
+// BENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // BE-NEXT:    store volatile i8 [[INC]], i8* [[TMP0]], align 1
 // BE-NEXT:    ret void
 //
@@ -906,6 +914,7 @@
 // LE-NEXT:    [[TMP0:%.*]] = getelementptr [[STRUCT_ST15:%.*]], %struct.st15* [[S:%.*]], i32 0, i32 0
 // LE-NEXT:    [[BF_LOAD:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // LE-NEXT:    [[INC:%.*]] = add i8 [[BF_LOAD]], 1
+// LENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // LE-NEXT:    store volatile i8 [[INC]], i8* [[TMP0]], align 1
 // LE-NEXT:    ret void
 //
@@ -914,6 +923,7 @@
 // BE-NEXT:    [[TMP0:%.*]] = getelementptr [[STRUCT_ST15:%.*]], %struct.st15* [[S:%.*]], i32 0, i32 0
 // BE-NEXT:    [[BF_LOAD:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // BE-NEXT:    [[INC:%.*]] = add i8 [[BF_LOAD]], 1
+// BENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // BE-NEXT:    store volatile i8 [[INC]], i8* [[TMP0]], align 1
 // BE-NEXT:    ret void
 //
@@ -1061,6 +1071,7 @@
 // LE-NEXT:    [[TMP0:%.*]] = bitcast %struct.st16* [[S:%.*]] to i32*
 // LE-NEXT:    [[BF_LOAD:%.*]] = load volatile i32, i32* [[TMP0]], align 4
 // LE-NEXT:    [[INC:%.*]] = add nsw i32 [[BF_LOAD]], 1
+// LENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i32, i32* [[TMP0]], align 4
 // LE-NEXT:    store volatile i32 [[INC]], i32* [[TMP0]], align 4
 // LE-NEXT:    ret void
 //
@@ -1069,6 +1080,7 @@
 // BE-NEXT:    [[TMP0:%.*]] = bitcast %struct.st16* [[S:%.*]] to i32*
 // BE-NEXT:    [[BF_LOAD:%.*]] = load volatile i32, i32* [[TMP0]], align 4
 // BE-NEXT:    [[INC:%.*]] = add nsw i32 [[BF_LOAD]], 1
+// BENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i32, i32* [[TMP0]], align 4
 // BE-NEXT:    store volatile i32 [[INC]], i32* [[TMP0]], align 4
 // BE-NEXT:    ret void
 //
@@ -1112,6 +1124,7 @@
 // LE-NEXT:    [[TMP1:%.*]] = bitcast i48* [[TMP0]] to i32*
 // LE-NEXT:    [[BF_LOAD:%.*]] = load volatile i32, i32* [[TMP1]], align 4
 // LE-NEXT:    [[INC:%.*]] = add nsw i32 [[BF_LOAD]], 1
+// LENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i32, i32* [[TMP1]], align 4
 // LE-NEXT:    store volatile i32 [[INC]], i32* [[TMP1]], align 4
 // LE-NEXT:    ret void
 //
@@ -1121,6 +1134,7 @@
 // BE-NEXT:    [[TMP1:%.*]] = bitcast i48* [[TMP0]] to i32*
 // BE-NEXT:    [[BF_LOAD:%.*]] = load volatile i32, i32* [[TMP1]], align 4
 // BE-NEXT:    [[INC:%.*]] = add nsw i32 [[BF_LOAD]], 1
+// BENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i32, i32* [[TMP1]], align 4
 // BE-NEXT:    store volatile i32 [[INC]], i32* [[TMP1]], align 4
 // BE-NEXT:    ret void
 //
@@ -1201,6 +1215,7 @@
 // LE-NEXT:    [[TMP0:%.*]] = getelementptr inbounds [[STRUCT_ST17:%.*]], %struct.st17* [[S:%.*]], i32 0, i32 0, i32 4
 // LE-NEXT:    [[BF_LOAD:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // LE-NEXT:    [[INC:%.*]] = add i8 [[BF_LOAD]], 1
+// LENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // LE-NEXT:    store volatile i8 [[INC]], i8* [[TMP0]], align 1
 // LE-NEXT:    ret void
 //
@@ -1209,6 +1224,7 @@
 // BE-NEXT:    [[TMP0:%.*]] = getelementptr inbounds [[STRUCT_ST17:%.*]], %struct.st17* [[S:%.*]], i32 0, i32 0, i32 4
 // BE-NEXT:    [[BF_LOAD:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // BE-NEXT:    [[INC:%.*]] = add i8 [[BF_LOAD]], 1
+// BENUMLOADS-NEXT:    [[BF_LOAD1:%.*]] = load volatile i8, i8* [[TMP0]], align 1
 // BE-NEXT:    store volatile i8 [[INC]], i8* [[TMP0]], align 1
 // BE-NEXT:    ret void
 //