Comment 74 for bug 417009

The patch on http://pastebin.ubuntu.com/395620/ is probably the one to go for, since it preserves 64-bit stack alignment and will work for target functions which take more than 4 arguments including this (they end up in a contiguous slab on the stack).

The exception unwinder is also told not to bother restore r0-r3 since this isn't necessary to conform to the ABI.