Intrinsify some ByteArray methods.

runtime/vm/assembler_x64.cc

Index: runtime/vm/assembler_x64.cc
diff --git a/runtime/vm/assembler_x64.cc b/runtime/vm/assembler_x64.cc
index 05b73f1ff944e608b62a7312f52dcfee9b70e13e..fd8f2189faa2c75469039e5f408878c0f773f455 100644
--- a/runtime/vm/assembler_x64.cc
+++ b/runtime/vm/assembler_x64.cc
@@ -323,8 +323,12 @@ void Assembler::movq(const Address& dst, const Immediate& imm) {
 }
 
 
+// MOVSXD

[srdjan, 2012/06/06 23:30:00]

Weird comment, remove?

[cshapiro, 2012/06/06 23:43:07]

I will remove it.

The curious thing about this instruction is that the manual calls it MOVSXD and
not MOVSX, probably because it has a completely different opcode from MOVSX.  I
think we may want to rename this instruction for the sake of sanity however,
using the GAS naming convention makes it hard to undo this entirely.

 void Assembler::movsxl(Register dst, const Address& src) {
-  UNIMPLEMENTED();
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitOperandREX(dst, src, REX_W);
+  EmitUint8(0x63);
+  EmitOperand(dst & 7, src);
 }