Add packed add and subtract to IA32 and X64 assemblers

runtime/vm/assembler_ia32.cc

Index: runtime/vm/assembler_ia32.cc
diff --git a/runtime/vm/assembler_ia32.cc b/runtime/vm/assembler_ia32.cc
index c04347ce382bf8e113b3241aeb50be99f60f016b..a1dfc13e397998247ec99b3a8668b3e09b31930f 100644
--- a/runtime/vm/assembler_ia32.cc
+++ b/runtime/vm/assembler_ia32.cc
@@ -571,6 +571,24 @@ void Assembler::addsd(XmmRegister dst, const Address& src) {
 }
 
 
+void Assembler::addpl(XmmRegister dst, XmmRegister src) {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitUint8(0x66);
+  EmitUint8(0x0F);
+  EmitUint8(0xFE);
+  EmitXmmRegisterOperand(dst, src);
+}
+
+
+void Assembler::subpl(XmmRegister dst, XmmRegister src) {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitUint8(0x66);
+  EmitUint8(0x0F);
+  EmitUint8(0xFA);
+  EmitXmmRegisterOperand(dst, src);
+}
+
+
 void Assembler::addps(XmmRegister dst, XmmRegister src) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitUint8(0x0F);