On Sep 28, 2007, at 2:38 PM, Duncan Sands wrote: > Hi Chris, > >>> Also >>> 5. Within foo, you need to check that nothing too complicated is >>> done to P1, for example it isn't stored in a global or passed to >>> some other function. >> >> Actually, worse case, you could just make a trampoline in foo. >> However, you're right that this is only worth doing if there are >> calls to the fn pointer in foo. OTOH, propagating the trampoline >> creation site down to foo will allow it to be further propagated into >> functions that foo might call. > > that could be very costly. Initializing a trampoline is not very > costly. What is costly is using it and then modifying the stack > contents where the trampoline was, because you get an icache flush. > Eg: if you push the trampoline down into a function called in a loop, > then you risk calling the trampoline then dirtying that part of the > stack (after function return, due to other local variables using that > part of the stack) and thus taking a large hit on every iteration.
Fair enough. :) -Chris _______________________________________________ llvm-commits mailing list llvm-commits@cs.uiuc.edu http://lists.cs.uiuc.edu/mailman/listinfo/llvm-commits
