Added command line flag --sync_with_push (default: true) to

emit 'push' instead of 'sub esp, xxx' followed by 'mov' instructions
Reduces generated code size by 10-15% on several benchmarks.
Done on ia32 and x64 (no sync operation in the virtual frame on ARM 
architecture)

Review URL: http://codereview.chromium.org/259058

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3032 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ia32/virtual-frame-ia32.cc

@@ -161,15 +161,16 @@ void VirtualFrame::SyncRange(int begin, int end) {
   // on the stack.
   int start = Min(begin, stack_pointer_ + 1);
 
-  // If positive we have to adjust the stack pointer.
-  int delta = end - stack_pointer_;
-  if (delta > 0) {
-    stack_pointer_ = end;
-    __ sub(Operand(esp), Immediate(delta * kPointerSize));
-  }
-
+  // Emit normal 'push' instructions for elements above stack pointer
+  // and use mov instructions if we are below stack pointer.
   for (int i = start; i <= end; i++) {
-    if (!elements_[i].is_synced()) SyncElementBelowStackPointer(i);
+    if (!elements_[i].is_synced()) {
+      if (i <= stack_pointer_) {
+        SyncElementBelowStackPointer(i);
+      } else {
+        SyncElementByPushing(i);
+      }
+    }
   }
 }
 

src/x64/virtual-frame-x64.cc

@@ -883,15 +883,16 @@ void VirtualFrame::SyncRange(int begin, int end) {
   // on the stack.
   int start = Min(begin, stack_pointer_ + 1);
 
-  // If positive we have to adjust the stack pointer.
-  int delta = end - stack_pointer_;
-  if (delta > 0) {
-    stack_pointer_ = end;
-    __ subq(rsp, Immediate(delta * kPointerSize));
-  }
-
+  // Emit normal 'push' instructions for elements above stack pointer
+  // and use mov instructions if we are below stack pointer.
   for (int i = start; i <= end; i++) {
-    if (!elements_[i].is_synced()) SyncElementBelowStackPointer(i);
+    if (!elements_[i].is_synced()) {
+      if (i <= stack_pointer_) {
+        SyncElementBelowStackPointer(i);
+      } else {
+        SyncElementByPushing(i);
+      }
+    }
   }
 }