Implement a simple register allocator that tries to keep instruction results in registers.

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 72bd938eb74664c3e0133b0228d395cd6284556c..deb5c138b07316a68cf8bca1e824a19ecbbf75e0 100644
--- a/runtime/vm/assembler_ia32.cc
+++ b/runtime/vm/assembler_ia32.cc
@@ -1293,6 +1293,16 @@ void Assembler::MoveRegister(Register to, Register from) {
 }
 
 
+void Assembler::PushRegister(Register r) {
+  pushl(r);
+}
+
+
+void Assembler::PopRegister(Register r) {
+  popl(r);
+}
+
+
 void Assembler::AddImmediate(Register reg, const Immediate& imm) {
   int value = imm.value();
   if (value > 0) {