public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug target/93802] gcc generates a rlwinm/or pair instead of a single rlwimi (powerpc)
[not found] <bug-93802-4@http.gcc.gnu.org/bugzilla/>
@ 2020-04-30 21:36 ` segher at gcc dot gnu.org
2024-03-06 2:53 ` guihaoc at gcc dot gnu.org
1 sibling, 0 replies; 2+ messages in thread
From: segher at gcc dot gnu.org @ 2020-04-30 21:36 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93802
Segher Boessenkool <segher at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |segher at gcc dot gnu.org
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed| |2020-04-30
--- Comment #1 from Segher Boessenkool <segher at gcc dot gnu.org> ---
Confirmed. Needs -m32.
There are complications from parameter passing. Making x a global doesn't
improve things: the zero-extend becomes part of the memory access, which
prevents us from optimising it well later.
Adding something like
x *= 42;
as extra first line doesn't work, either:
Failed to match this instruction:
(set (reg:SI 124)
(ior:SI (and:SI (reg:SI 123)
(const_int 65534 [0xfffe]))
(ashift:SI (reg:SI 123)
(const_int 16 [0x10]))))
(Note combine has figured out the low bit is always zero, How helpful ;-) )
But with
x *= 421;
we get
f:
mulli 3,3,421 # 6 [c=8 l=4] mulsi3/1
rlwimi 3,3,16,0,31-16 # 14 [c=4 l=4] *rotlsi3_insert_3
blr # 22 [c=4 l=4] simple_return
which is exactly what we wanted.
Both the original case and the "even" case should work better if we had
better known bits tracking (the "even" one could maybe be made to work
already, even, in target code).
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug target/93802] gcc generates a rlwinm/or pair instead of a single rlwimi (powerpc)
[not found] <bug-93802-4@http.gcc.gnu.org/bugzilla/>
2020-04-30 21:36 ` [Bug target/93802] gcc generates a rlwinm/or pair instead of a single rlwimi (powerpc) segher at gcc dot gnu.org
@ 2024-03-06 2:53 ` guihaoc at gcc dot gnu.org
1 sibling, 0 replies; 2+ messages in thread
From: guihaoc at gcc dot gnu.org @ 2024-03-06 2:53 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93802
HaoChen Gui <guihaoc at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|NEW |RESOLVED
CC| |guihaoc at gcc dot gnu.org
--- Comment #2 from HaoChen Gui <guihaoc at gcc dot gnu.org> ---
It's already fixed by f4a3cea3fb02. Now it generates a single rlwimi.
rlwimi 3,3,16,0,31-16
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2024-03-06 2:53 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
[not found] <bug-93802-4@http.gcc.gnu.org/bugzilla/>
2020-04-30 21:36 ` [Bug target/93802] gcc generates a rlwinm/or pair instead of a single rlwimi (powerpc) segher at gcc dot gnu.org
2024-03-06 2:53 ` guihaoc at gcc dot gnu.org
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).