[codegen] Use xchg instead of push/pop for swap

R=sigurds@chromium.org

Change-Id: Id22a44fa15827d5c076496d872fe3be7da360b5e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1678356
Auto-Submit: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62383}

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

@@ -4517,9 +4517,7 @@ void CodeGenerator::AssembleSwap(InstructionOperand* source,
       if (source->IsRegister()) {
         Register src = g.ToRegister(source);
         Register dst = g.ToRegister(destination);
-        __ push(src);
-        __ mov(src, dst);
-        __ pop(dst);
+        __ xchg(src, dst);
       } else {
         DCHECK(source->IsFPRegister());
         XMMRegister src = g.ToDoubleRegister(source);