[hack] flags for xchg perf study

src/compiler/ia32/code-generator-ia32.cc

Index: src/compiler/ia32/code-generator-ia32.cc
diff --git a/src/compiler/ia32/code-generator-ia32.cc b/src/compiler/ia32/code-generator-ia32.cc
index f63bc22e4344fe65a875ea3c7cc341a98caa362a..16144c488c7d942b71964800d53e2e09c66b3ffa 100644
--- a/src/compiler/ia32/code-generator-ia32.cc
+++ b/src/compiler/ia32/code-generator-ia32.cc
@@ -1616,9 +1616,21 @@ void CodeGenerator::AssembleSwap(InstructionOperand* source,
     // Register-register.
     Register src = g.ToRegister(source);
     Register dst = g.ToRegister(destination);
-    __ push(src);
-    __ mov(src, dst);
-    __ pop(dst);
+    if (FLAG_use_xor) {
+      __ xor_(src, dst);
+      __ xor_(dst, src);
+      __ xor_(src, dst);
+    } else if (FLAG_use_xchg) {
+      __ xchg(src, dst);
+    } else if (FLAG_use_movs) {
+      __ mov(esi, src);
+      __ mov(src, dst);
+      __ mov(dst, esi);
+    } else {
+      __ push(src);
+      __ mov(src, dst);
+      __ pop(dst);
+    }
   } else if (source->IsRegister() && destination->IsStackSlot()) {
     // Register-memory.
     Register src = g.ToRegister(source);