Index: lib/Target/ARM/ARM.td
===================================================================
--- lib/Target/ARM/ARM.td
+++ lib/Target/ARM/ARM.td
@@ -363,6 +363,11 @@
 def FeatureUseAA : SubtargetFeature<"use-aa", "UseAA", "true",
                                     "Use alias analysis during codegen">;
 
+// Armv8.5-A extensions
+
+def FeatureSpecCtrl : SubtargetFeature<"specctrl", "HasSpecCtrl", "true",
+  "Enable speculation control barrier" >;
+
 //===----------------------------------------------------------------------===//
 // ARM architecture class
 //
@@ -453,8 +458,8 @@
                                    [HasV8_3aOps, FeatureDotProd]>;
 
 def HasV8_5aOps   : SubtargetFeature<"v8.5a", "HasV8_5aOps", "true",
-                                   "Support Armv8.5-A instructions",
-                                   [HasV8_4aOps]>;
+                                     "Support Armv8.5-A instructions",
+                                     [HasV8_4aOps, FeatureSpecCtrl]>;
 
 //===----------------------------------------------------------------------===//
 // ARM Processor subtarget features.
Index: lib/Target/ARM/ARMInstrInfo.td
===================================================================
--- lib/Target/ARM/ARMInstrInfo.td
+++ lib/Target/ARM/ARMInstrInfo.td
@@ -391,6 +391,10 @@
 
 def GenExecuteOnly : Predicate<"Subtarget->genExecuteOnly()">;
 
+// Armv8.5-A extensions
+def HasSpecCtrl      : Predicate<"Subtarget->hasSpecCtrl()">,
+                       AssemblerPredicate<"FeatureSpecCtrl", "specctrl">;
+
 //===----------------------------------------------------------------------===//
 // ARM Flag Definitions.
 
@@ -4875,6 +4879,13 @@
 
 }
 
+// Armv8.5-A speculation barrier
+def SB : AInoP<(outs), (ins), MiscFrm, NoItinerary, "sb", "", []>,
+         Requires<[IsARM, HasSpecCtrl]>, Sched<[]> {
+  let Inst{31-0} = 0xf57ff070;
+  let Unpredictable = 0x000fff0f;
+}
+
 let usesCustomInserter = 1, Defs = [CPSR] in {
 
 // Pseudo instruction that combines movs + predicated rsbmi
Index: lib/Target/ARM/ARMInstrThumb2.td
===================================================================
--- lib/Target/ARM/ARMInstrThumb2.td
+++ lib/Target/ARM/ARMInstrThumb2.td
@@ -3231,6 +3231,13 @@
 }
 }
 
+// Armv8.5-A speculation barrier
+def t2SB : Thumb2XI<(outs), (ins), AddrModeNone, 4, NoItinerary, "sb", "", []>,
+           Requires<[IsThumb2, HasSpecCtrl]>, Sched<[]> {
+  let Inst{31-0} = 0xf3bf8f70;
+  let Unpredictable = 0x000f2f0f;
+}
+
 class T2I_ldrex<bits<4> opcod, dag oops, dag iops, AddrMode am, int sz,
                 InstrItinClass itin, string opc, string asm, string cstr,
                 list<dag> pattern, bits<4> rt2 = 0b1111>
Index: lib/Target/ARM/ARMSubtarget.h
===================================================================
--- lib/Target/ARM/ARMSubtarget.h
+++ lib/Target/ARM/ARMSubtarget.h
@@ -416,6 +416,9 @@
   /// UseSjLjEH - If true, the target uses SjLj exception handling (e.g. iOS).
   bool UseSjLjEH = false;
 
+  /// Has speculation barrier
+  bool HasSpecCtrl = false;
+
   /// Implicitly convert an instruction to a different one if its immediates
   /// cannot be encoded. For example, ADD r0, r1, #FFFFFFFF -> SUB r0, r1, #1.
   bool NegativeImmediates = true;
@@ -625,6 +628,7 @@
   bool hasDSP() const { return HasDSP; }
   bool useNaClTrap() const { return UseNaClTrap; }
   bool useSjLjEH() const { return UseSjLjEH; }
+  bool hasSpecCtrl() const { return HasSpecCtrl; }
   bool genLongCalls() const { return GenLongCalls; }
   bool genExecuteOnly() const { return GenExecuteOnly; }
 
Index: lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -5720,7 +5720,8 @@
       Mnemonic == "vmovx" || Mnemonic == "vins" ||
       Mnemonic == "vudot" || Mnemonic == "vsdot" ||
       Mnemonic == "vcmla" || Mnemonic == "vcadd" ||
-      Mnemonic == "vfmal" || Mnemonic == "vfmsl") {
+      Mnemonic == "vfmal" || Mnemonic == "vfmsl" ||
+      Mnemonic == "sb") {
     // These mnemonics are never predicable
     CanAcceptPredicationCode = false;
   } else if (!isThumb()) {
Index: test/MC/ARM/armv8.5a-specctrl-error-thumb.s
===================================================================
--- /dev/null
+++ test/MC/ARM/armv8.5a-specctrl-error-thumb.s
@@ -0,0 +1,6 @@
+// RUN: not llvm-mc -triple thumbv8 -show-encoding -mattr=+specctrl < %s 2>&1 | FileCheck %s
+
+it eq
+sbeq
+
+// CHECK: instruction 'sb' is not predicable, but condition code specified
Index: test/MC/ARM/armv8.5a-specctrl-error.s
===================================================================
--- /dev/null
+++ test/MC/ARM/armv8.5a-specctrl-error.s
@@ -0,0 +1,5 @@
+// RUN: not llvm-mc -triple armv8 -show-encoding -mattr=+specctrl < %s 2>&1 | FileCheck %s
+
+sbeq
+
+// CHECK: instruction 'sb' is not predicable
Index: test/MC/ARM/armv8.5a-specctrl.s
===================================================================
--- /dev/null
+++ test/MC/ARM/armv8.5a-specctrl.s
@@ -0,0 +1,15 @@
+// RUN:     llvm-mc -triple armv8   -show-encoding -mattr=+specctrl < %s      | FileCheck %s
+// RUN:     llvm-mc -triple armv8   -show-encoding -mattr=+v8.5a    < %s      | FileCheck %s
+// RUN: not llvm-mc -triple armv8   -show-encoding -mattr=-specctrl < %s 2>&1 | FileCheck %s --check-prefix=NOSB
+// RUN:     llvm-mc -triple thumbv8 -show-encoding -mattr=+specctrl < %s      | FileCheck %s --check-prefix=THUMB
+// RUN:     llvm-mc -triple thumbv8 -show-encoding -mattr=+v8.5a    < %s      | FileCheck %s --check-prefix=THUMB
+// RUN: not llvm-mc -triple thumbv8 -show-encoding -mattr=-specctrl < %s 2>&1 | FileCheck %s --check-prefix=NOSB
+
+// Flag manipulation
+sb
+
+// CHECK: sb    @ encoding: [0x70,0xf0,0x7f,0xf5]
+// THUMB: sb    @ encoding: [0xbf,0xf3,0x70,0x8f]
+
+// NOSB: instruction requires: specctrl
+// NOSB-NEXT: sb
Index: test/MC/Disassembler/ARM/armv8.5a-specctrl-thumb.txt
===================================================================
--- /dev/null
+++ test/MC/Disassembler/ARM/armv8.5a-specctrl-thumb.txt
@@ -0,0 +1,9 @@
+# RUN: llvm-mc -triple=thumbv8 -mattr=+specctrl -disassemble < %s      | FileCheck %s
+# RUN: llvm-mc -triple=thumbv8 -mattr=+v8.5a    -disassemble < %s      | FileCheck %s
+# RUN: llvm-mc -triple=thumbv8 -mattr=-specctrl -disassemble < %s 2>&1 | FileCheck %s --check-prefix=NOSB
+
+0xbf 0xf3 0x70 0x8f
+
+# CHECK: sb
+# NOSB: invalid instruction encoding
+# NOSB-NEXT: 0xbf 0xf3 0x70 0x8f
Index: test/MC/Disassembler/ARM/armv8.5a-specctrl.txt
===================================================================
--- /dev/null
+++ test/MC/Disassembler/ARM/armv8.5a-specctrl.txt
@@ -0,0 +1,9 @@
+# RUN: llvm-mc -triple=armv8 -mattr=+specctrl -disassemble < %s      | FileCheck %s
+# RUN: llvm-mc -triple=armv8 -mattr=+v8.5a    -disassemble < %s      | FileCheck %s
+# RUN: llvm-mc -triple=armv8 -mattr=-specctrl -disassemble < %s 2>&1 | FileCheck %s --check-prefix=NOSB
+
+0x70 0xf0 0x7f 0xf5
+
+# CHECK:    sb
+# NOSB: invalid instruction encoding
+# NOSB-NEXT: 0x70 0xf0 0x7f 0xf5