> It looks at register that respect the constraints of all the instructions in
> the set and tries to pick one in the preferred class for all the
> instructions involved. This is generally useful for any pass that wants to
> do register renaming. However it also contains some logic to only select
> the register that also haven't been used for a longer time than the
> register that should be replaced. This bit is specific to the register
> renaming pass and makes the function unusable for this new pass as a result
> which forces us to do a copy of the function.
>
> This patch adds an extra parameter to skip this check and only consider the
> constraints and tries to pick a register in the preferred class.
OK on principle but...
> 2014-11-14 Thomas Preud'homme <thomas.preudho...@arm.com>
>
> * regrename.c (find_best_rename_reg): Rename to ...
> (find_rename_reg): This. Also add a parameter to skip tick check.
> * regrename.h: Likewise.
> * config/c6x/c6x.c: Adapt to above renaming.
Missing function in config/c6x/c6x.c entry.
> @@ -408,8 +410,13 @@ find_best_rename_reg (du_head_p this_head, enum
> reg_class super_class, && ((pass == 0
> && !TEST_HARD_REG_BIT (reg_class_contents[preferred_class],
> best_new_reg))
> - || tick[best_new_reg] > tick[new_reg]))
> - best_new_reg = new_reg;
> + || !best_rename || tick[best_new_reg] > tick[new_reg]))
> + {
> + if (best_rename)
> + best_new_reg = new_reg;
> + else
> + return new_reg;
> + }
> }
> if (pass == 0 && best_new_reg != old_reg)
> break;
Please write it like so:
if (!check_new_reg_p (old_reg, new_reg, this_head, *unavailable))
continue;
if (!best_rename)
return new_reg;
/* In the first pass, we force the renaming of registers that
don't belong to PREFERRED_CLASS to registers that do, even
though the latters were used not very long ago. *
if ((pass == 0
&& !TEST_HARD_REG_BIT (reg_class_contents[preferred_class],
best_new_reg))
|| tick[best_new_reg] > tick[new_reg]))
best_new_reg = new_reg;
--
Eric Botcazou
