https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64537
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Target Milestone|--- |9.0
Status|NEW |RESOLVED
--- Comment #7 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
GCC9+ does:
subs x3, x0, x1, sxth 3
add w1, w2, w1, sxth
add w1, w1, w3
add w0, w2, w0
csel w0, w1, w0, ne
ret
GCC 8 produced:
sxth w1, w1
subs x3, x0, x1, sxth 3
add w1, w1, w2
add w1, w1, w3
add w0, w2, w0
csel w0, w1, w0, ne
ret
GCC 9's combine is able to do this:
Trying 3 -> 8:
3: r99:SI=sign_extend(x1:HI)
REG_DEAD x1:HI
8: r101:DI=sign_extend(r99:SI#0)
Failed to match this instruction:
(parallel [
(set (reg:DI 101 [ b ])
(sign_extend:DI (reg:HI 1 x1 [ b ])))
(set (reg/v:SI 99 [ b ])
(sign_extend:SI (reg:HI 1 x1 [ b ])))
])
Failed to match this instruction:
(parallel [
(set (reg:DI 101 [ b ])
(sign_extend:DI (reg:HI 1 x1 [ b ])))
(set (reg/v:SI 99 [ b ])
(sign_extend:SI (reg:HI 1 x1 [ b ])))
])
Successfully matched this instruction:
(set (reg/v:SI 99 [ b ])
(sign_extend:SI (reg:HI 1 x1 [ b ])))
Successfully matched this instruction:
(set (reg:DI 101 [ b ])
(sign_extend:DI (reg:HI 1 x1 [ b ])))
allowing combination of insns 3 and 8
original costs 4 + 4 = 8
replacement costs 4 + 4 = 8
So fixed by r9-2064.
