Add DMB instruction to the ARM integrated assembler.

src/IceInstARM32.cpp

Index: src/IceInstARM32.cpp
diff --git a/src/IceInstARM32.cpp b/src/IceInstARM32.cpp
index 5cc0a15ea30039e5deabc56b6f70bca3eced7aec..76140e8541683b60e61a1b68358ea64fd21811ef 100644
--- a/src/IceInstARM32.cpp
+++ b/src/IceInstARM32.cpp
@@ -1710,6 +1710,15 @@ void InstARM32Dmb::emit(const Cfg *Func) const {
          "sy";
 }
 
+void InstARM32Dmb::emitIAS(const Cfg *Func) const {
+  assert(getSrcSize() == 0);
+  auto *Asm = Func->getAssembler<ARM32::AssemblerARM32>();
+  constexpr ARM32::IValueT SyOption = 0xF; // i.e. 1111
+  Asm->dmb(SyOption);
+  if (Asm->needsTextFixup())
+    emitUsingTextFixup(Func);
+}
+
 void InstARM32Dmb::dump(const Cfg *Func) const {
   if (!BuildDefs::dump())
     return;