I'm am still struggling with a good solution that avoids unneeded saves of parameter registers.
To solve problem all I need to know are the registers actually used for parameters. Since the caller assumes all of these are clobbered by callee - they should never need to be saved. DF_REG_DEF_COUNT is showing 1 artificial def for all POTENTIAL parameter registers - not just the ones that are really used (since it uses target FUNCTION_ARG_REGNO_P to get parameter registers) So the DF artificial defs are useless in trying to find real parameter registers. That seem to require going over all DF chains to work out which registers are externally defined. DF does not solve problem for me. There has got to be an easier way of finding parameter registers used by function. Ideas? Seongbae Park (박성배, 朴成培) wrote: > You can use DF_REG_DEF_COUNT() - if this is indeed a parameter register, > there should be only one def (artificial def) or no def at all. > Or if you want to see all defs for the reg, > follow DF_REG_DEF_CHAIN(). > > Seongbae > > On Wed, Feb 27, 2008 at 6:03 PM, Andrew Hutchinson > <[EMAIL PROTECTED]> wrote: > >> Register contains parameter that is passed to function. This register >> is not part of call used set. >> >> If this type of register were modified by function, then it would be >> saved by function. >> >> If this register is not modified by function, it should not be saved. >> This is true even if function is not a leaf function (as same register >> would be preserved by deeper calls) >> >> >> Andy >> >> >> >> >> >> Seongbae Park (박성배, 朴成培) wrote: >> > On Wed, Feb 27, 2008 at 5:16 PM, Andrew Hutchinson >> > <[EMAIL PROTECTED]> wrote: >> > >> >> Register saves by prolog (pushes) are typically made with reference to >> >> "df_regs_ever_live_p()" or "regs_ever_live. "|| >> >> >> >> If my understanding is correct, these calls reflect register USEs and >> >> not register DEFs. So if register is used in a function, but not >> >> otherwise changed, it will get pushed unnecessarily on stack by prolog. >> >> >> > >> > This implies that the register is either a global register >> > or a parameter register, in either case it won't be saved/restored >> > as callee save. >> > What kind of a register is it and how com there's only use of it in a >> function >> > but it's not a global ? >> > >> > Seongbae >> > >> > >> >> > > > >
