Currently funclets reuse the same stack slots that are used in the parent function for saving callee-saved xmm registers. If the parent function modifies a callee-saved xmm register before an excpetion is thrown, the catch handler will overwrite the original saved value.
This patch allocates a second stack slot to be used in the EH funclets for saving these same registers. Long term, it would be better to determine actual CSR use by the funclets and only allocate the extra space when needed.