CanvasRenderingContext2D.drawImage is so slow in a clipping region

This is my code
context.save();
context.beginPath();
//loop
clearRect(x,y,width,height);
context.rect(x,y,width,height);
//loop end
context.clip();
//loop
context.drawImage(........)
//loop end
context.restore();
The drawImage method is very fast if there is no clipping area. But the fps is drop to 10% if there are clipping regions.
Any workaround?

Hi Rob,
Thank you for reply.
Assume there are more than 50 logic layers in my game, I don't think it's a good idea to create so many canvas elements.
I think it maybe a bug of IE, because the draw cost is so high after I added the clipping regions.
Do you have any ideas on this issue? Both IE on desktop and Windows Phone have this issue.
Thank you.

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