On Thu, Apr 1, 2010 at 8:10 PM, Andrew Haley <a...@redhat.com> wrote: > On 28/03/10 15:45, Carrot Wei wrote: >> Hi >> >> The detailed description of the optimization is at >> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43129. This is an ARM >> specific optimization. >> >> This optimization uses one less register (the register hold the GOT >> base), to get this beneficial the ideal place for it should be before >> register allocation. >> >> Usually expand pass generates instructions to load global variable's >> address from GOT entry for each access of the global variable. Later >> cse/gcse passes can remove many of them. In order to precisely model >> the cost, this optimization should be put after some cse/gcse passes. >> >> So what is the best place for this optimization? Is there any existed >> pass can be enhanced with this optimization? Or should I add a new >> pass? > > The obvious place is machine-dependent reorg, which is a very late pass.
Yes, and after register allocation, i.e. too late for Guozhi. Basically there is no place right now to stuff a pass like that. Question is: Is this optimization really, reallyreallyreally so target specific that a target-independent pass is not the better option? Ciao! Steven
