Add Sxtb instructions to ARM integrated assembler.

src/IceInstARM32.cpp

Index: src/IceInstARM32.cpp
diff --git a/src/IceInstARM32.cpp b/src/IceInstARM32.cpp
index 2590a10ed988fd08c81d3071166940c501128775..7fc58831b334c2487cf4f06ed4f2ceed29fd6a41 100644
--- a/src/IceInstARM32.cpp
+++ b/src/IceInstARM32.cpp
@@ -1185,6 +1185,14 @@ template <> void InstARM32Mvn::emitIAS(const Cfg *Func) const {
     emitUsingTextFixup(Func);
 }
 
+template <> void InstARM32Sxt::emitIAS(const Cfg *Func) const {
+  assert(getSrcSize() == 1);
+  auto *Asm = Func->getAssembler<ARM32::AssemblerARM32>();
+  Asm->sxt(getDest(), getSrc(0), getPredicate());
+  if (Asm->needsTextFixup())
+    emitUsingTextFixup(Func);
+}
+
 template <> void InstARM32Uxt::emitIAS(const Cfg *Func) const {
   assert(getSrcSize() == 1);
   auto *Asm = Func->getAssembler<ARM32::AssemblerARM32>();