On Wed, Aug 6, 2008 at 1:58 PM, Patrick R. Michaud <[EMAIL PROTECTED]> wrote: > On Tue, Aug 05, 2008 at 10:51:08AM -0700, Klaas-Jan Stol wrote: >> From pdd19: >> >> The optional C<:unique_reg> modifier will force the register allocator to >> associate the identifier with a unique register for the duration of the >> subroutine. >> >> >> This, however, does not document /why/ you would want to do that. Why do we >> have this flag? >> Maybe add an example. > > Sometimes the register allocator will re-use a register when it's > important that the register not be reused.
Can you describe a situation where this occurs that isn't a bug in the register allocator? > The :unique_reg flag > is supposed to guarantee that whatever register is allocated for > a symbol is used _only_ for that symbol and not re-allocated. > > PGE has used :unique_reg to try to "turn off" the register allocator > for the subs it generates, which tended to perform badly both in > terms of speed and in terms of correctly allocating registers. > (All of PGE's generated subs use a small fixed number of registers > and so the register allocator is a detriment and not a help.) > > Pm > -- Will "Coke" Coleda
