https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96017
Segher Boessenkool <segher at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2020-07-01
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
--- Comment #5 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Yes, or we should duplicate more of the function earlier (before RA),
for example the return tails.
Separate shrink wrapping does not duplicate code (it can easily
explode code size -- it will be interesting to see how much it can
help, if we restrict it somehow). But it is r31 already before
shrink-wrapping -- we need some renaming / copying of registers (like
in Peter's code) to get rid of it. In an example like this it is
quite useful, but in a lot of "real world" code there are no free
volatile registers to scarf up. Or that was my impression anyway,
when I last looked at this. Time to revisit it...
(The "ELFv1" code is just
.L.test:
lwz 9,0(3)
addis 10,2,.LC0@toc@ha
ld 10,.LC0@toc@l(10)
std 31,-8(1)
stdu 1,-128(1)
lwa 31,0(10)
cmpwi 0,9,0
bne 0,.L8
addi 1,1,128
mr 3,31
ld 31,-8(1)
blr
.p2align 4,,15
.L8:
mflr 0
std 0,144(1)
bl slowpath
nop
ld 0,144(1)
addi 1,1,128
mr 3,31
ld 31,-8(1)
mtlr 0
blr
which feels simpler... but it is kind of the same?
