On 27/04/16 16:22, Torsten Duwe wrote: > Hi Maxim, > > thanks for starting the work on this; I have added the missing > command line option. It builds now and the resulting compiler generates > a linux kernel with the desired properties, so work can continue there. > > Torsten
i guess the flag should be documented in invoke.texi it's not clear what N means in -fprolog-pad=N, how location recording is enabled and how it interacts with -fipa-ra. (-pg disables -fipa-ra, but -fprolog-pad works without -pg.) with -mfentry, by default the user only has to implement the fentry call (linux wants nops there, but e.g. glibc could use -pg -mfentry for profiling on aarch64 and the target specific details are easier to document for an -m option than for something general). the nop-padding is more general, but the size and layout of nops and the call abi will be target specific and the user will most likely need to modify the binary (to get the right sequence) which needs additional tooling. i don't know who might use it other than linux (which already has tools to deal with -mfentry). i'm not against nop-padding, but i think more evidence is needed that the generalization is a good idea and users can deal with the resulting issues.
