Re: load large immediate

[Joern Rennecke <amylaar at spamcop dot net>]

Quoting daniel tian <daniel.xntian@gmail.com>:

> 2009/2/26 Joern Rennecke <amylaar@spamcop.net>:
> > > the address label "common_reg " used many times. I think it will
> > > load one time. But after optimized with '-Os' or '-O2', it still loads
> > > the label "common_reg " six times..
> >
> > Previously, you could define LEGITIMIZE_ADDRESS and
> > LEGITIMIZE_RELOAD_ADDRESS
> > to get reasonable code. ÂHowever, that no longer works in gcc 4.4, see
> > PR38785.
> >
> > I have a patch set; if you like, I can it to you. ÂNote, however, that it is
> > not known if the FSF have a relevant valid Copyright assignment on file.
>
> I port the gcc with 4.0.2 version. But How to add the code in
> LEGITIMIZE_RELOAD_ADDRESS. Do you have any example? Thank you very
> much.

Yes, there are a number of examples in config/*/*.h - just doing a
grep should give you a goo selection.  The port where this macro
has been added first, in order to avoid unnecessary repetition of
stack slot address additions, was the SH port.
The SFmode part is a later addition, which is different because the
SH3E (and the later 32 bit SH family members with hardware floating
point) don't have REG+offset addressing for floating point registers,
but they have REG+index addressing.
The basic operation of the macro is explained in doc/tm.texi .
In order to handle pseudos that are equivalent to a constant,
you need to allow registers that are not suitable as a base
for REG_OK_STRICT_P (because pseudos aren't), which have
reg_equiv_constant set.
You'll have to take the value in reg_equiv_constant and
do necessary arithmetic with plus_constant in order to compute
the value to be used in push_reload.