Add addw support to x86 and x64.

Test: assembler_x86_64_test assembler_x86_test
Change-Id: I2cfb815f15fa3df393bbeb4043ec208b3bdd9081
diff --git a/compiler/utils/x86/assembler_x86.cc b/compiler/utils/x86/assembler_x86.cc
index 9fcede5..8640e2d 100644
--- a/compiler/utils/x86/assembler_x86.cc
+++ b/compiler/utils/x86/assembler_x86.cc
@@ -2100,6 +2100,14 @@
 }
 
 
+void X86Assembler::addw(const Address& address, const Immediate& imm) {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  CHECK(imm.is_uint16() || imm.is_int16()) << imm.value();
+  EmitUint8(0x66);
+  EmitComplex(0, address, imm, /* is_16_op */ true);
+}
+
+
 void X86Assembler::adcl(Register reg, const Immediate& imm) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitComplex(2, Operand(reg), imm);
@@ -2751,14 +2759,20 @@
 }
 
 
-void X86Assembler::EmitImmediate(const Immediate& imm) {
-  EmitInt32(imm.value());
+void X86Assembler::EmitImmediate(const Immediate& imm, bool is_16_op) {
+  if (is_16_op) {
+    EmitUint8(imm.value() & 0xFF);
+    EmitUint8(imm.value() >> 8);
+  } else {
+    EmitInt32(imm.value());
+  }
 }
 
 
 void X86Assembler::EmitComplex(int reg_or_opcode,
                                const Operand& operand,
-                               const Immediate& immediate) {
+                               const Immediate& immediate,
+                               bool is_16_op) {
   CHECK_GE(reg_or_opcode, 0);
   CHECK_LT(reg_or_opcode, 8);
   if (immediate.is_int8()) {
@@ -2769,11 +2783,11 @@
   } else if (operand.IsRegister(EAX)) {
     // Use short form if the destination is eax.
     EmitUint8(0x05 + (reg_or_opcode << 3));
-    EmitImmediate(immediate);
+    EmitImmediate(immediate, is_16_op);
   } else {
     EmitUint8(0x81);
     EmitOperand(reg_or_opcode, operand);
-    EmitImmediate(immediate);
+    EmitImmediate(immediate, is_16_op);
   }
 }