Index: llvm/lib/Target/ARM/ARMInstrThumb2.td
===================================================================
--- llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -4848,9 +4848,15 @@
                   (t2TSTrr rGPR:$Rn, rGPR:$Rm, pred:$p)>;
 
 // Memory barriers
+def : InstAlias<"dmb${p}.w\t$opt", (t2DMB memb_opt:$opt, pred:$p), 0>, Requires<[HasDB]>;
 def : InstAlias<"dmb${p}", (t2DMB 0xf, pred:$p), 0>, Requires<[HasDB]>;
+def : InstAlias<"dmb${p}.w", (t2DMB 0xf, pred:$p), 0>, Requires<[HasDB]>;
+def : InstAlias<"dsb${p}.w\t$opt", (t2DSB memb_opt:$opt, pred:$p), 0>, Requires<[HasDB]>;
 def : InstAlias<"dsb${p}", (t2DSB 0xf, pred:$p), 0>, Requires<[HasDB]>;
+def : InstAlias<"dsb${p}.w", (t2DSB 0xf, pred:$p), 0>, Requires<[HasDB]>;
+def : InstAlias<"isb${p}.w\t$opt", (t2ISB memb_opt:$opt, pred:$p), 0>, Requires<[HasDB]>;
 def : InstAlias<"isb${p}", (t2ISB 0xf, pred:$p), 0>, Requires<[HasDB]>;
+def : InstAlias<"isb${p}.w", (t2ISB 0xf, pred:$p), 0>, Requires<[HasDB]>;
 
 // Non-predicable aliases of a predicable DSB: the predicate is (14, 0) where
 // 14 = AL (always execute) and 0 = "instruction doesn't read the CPSR".
Index: llvm/test/MC/ARM/basic-thumb2-instructions.s
===================================================================
--- llvm/test/MC/ARM/basic-thumb2-instructions.s
+++ llvm/test/MC/ARM/basic-thumb2-instructions.s
@@ -674,6 +674,7 @@
         dmb #0x0
 
         dmb sy
+        dmb.w sy
         dmb st
         dmb sh
         dmb ish
@@ -686,6 +687,7 @@
         dmb osh
         dmb oshst
         dmb
+        dmb.w
 
 @ CHECK: dmb	sy                      @ encoding: [0xbf,0xf3,0x5f,0x8f]
 @ CHECK: dmb	st                      @ encoding: [0xbf,0xf3,0x5e,0x8f]
@@ -704,6 +706,7 @@
 @ CHECK: dmb	#0x1                    @ encoding: [0xbf,0xf3,0x51,0x8f]
 @ CHECK: dmb	#0x0                    @ encoding: [0xbf,0xf3,0x50,0x8f]
 
+@ CHECK: dmb	sy                      @ encoding: [0xbf,0xf3,0x5f,0x8f]
 @ CHECK: dmb	sy                      @ encoding: [0xbf,0xf3,0x5f,0x8f]
 @ CHECK: dmb	st                      @ encoding: [0xbf,0xf3,0x5e,0x8f]
 @ CHECK: dmb	ish                     @ encoding: [0xbf,0xf3,0x5b,0x8f]
@@ -717,6 +720,7 @@
 @ CHECK: dmb	osh                     @ encoding: [0xbf,0xf3,0x53,0x8f]
 @ CHECK: dmb	oshst                   @ encoding: [0xbf,0xf3,0x52,0x8f]
 @ CHECK: dmb	sy                      @ encoding: [0xbf,0xf3,0x5f,0x8f]
+@ CHECK: dmb	sy                      @ encoding: [0xbf,0xf3,0x5f,0x8f]
 
 
 @------------------------------------------------------------------------------
@@ -740,6 +744,7 @@
         dsb #0x0
 
         dsb sy
+        dsb.w sy
         dsb st
         dsb sh
         dsb ish
@@ -752,6 +757,7 @@
         dsb osh
         dsb oshst
         dsb
+        dsb.w
 
 @ CHECK: dsb	sy                      @ encoding: [0xbf,0xf3,0x4f,0x8f]
 @ CHECK: dsb	st                      @ encoding: [0xbf,0xf3,0x4e,0x8f]
@@ -770,6 +776,7 @@
 @ CHECK: dsb	#0x1                    @ encoding: [0xbf,0xf3,0x41,0x8f]
 @ CHECK: ssbb                           @ encoding: [0xbf,0xf3,0x40,0x8f]
 
+@ CHECK: dsb	sy                      @ encoding: [0xbf,0xf3,0x4f,0x8f]
 @ CHECK: dsb	sy                      @ encoding: [0xbf,0xf3,0x4f,0x8f]
 @ CHECK: dsb	st                      @ encoding: [0xbf,0xf3,0x4e,0x8f]
 @ CHECK: dsb	ish                     @ encoding: [0xbf,0xf3,0x4b,0x8f]
@@ -783,6 +790,7 @@
 @ CHECK: dsb	osh                     @ encoding: [0xbf,0xf3,0x43,0x8f]
 @ CHECK: dsb	oshst                   @ encoding: [0xbf,0xf3,0x42,0x8f]
 @ CHECK: dsb	sy                      @ encoding: [0xbf,0xf3,0x4f,0x8f]
+@ CHECK: dsb	sy                      @ encoding: [0xbf,0xf3,0x4f,0x8f]
 
 
 @------------------------------------------------------------------------------
@@ -809,10 +817,14 @@
 @ ISB
 @------------------------------------------------------------------------------
         isb sy
+        isb.w sy
         isb
+        isb.w
         isb #15
         isb #1
 
+@ CHECK: isb	sy                      @ encoding: [0xbf,0xf3,0x6f,0x8f]
+@ CHECK: isb	sy                      @ encoding: [0xbf,0xf3,0x6f,0x8f]
 @ CHECK: isb	sy                      @ encoding: [0xbf,0xf3,0x6f,0x8f]
 @ CHECK: isb	sy                      @ encoding: [0xbf,0xf3,0x6f,0x8f]
 @ CHECK: isb	sy                      @ encoding: [0xbf,0xf3,0x6f,0x8f]