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[Bug middle-end/35141] ARM: Constant generation inside a loop: Missed optimization opportunity
- From: "alexandre dot nunes at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 11 Feb 2008 21:10:31 -0000
- Subject: [Bug middle-end/35141] ARM: Constant generation inside a loop: Missed optimization opportunity
- References: <bug-35141-15246@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #4 from alexandre dot nunes at gmail dot com 2008-02-11 21:10 -------
(In reply to comment #2)
> Also using a volatile pointer may prevent optimization, so don't use it if
> not strictly needed (or at least don't expect optimized code).
>
> Can you try 4.3 as suggested?
>
Ok, PR35071 was the only blocker. I did a bad thing in order to bypass it (it
only affected a non-default [for me] target on my multilib config) and get the
whole thing to compile, and the result is:
whatever:
@ args = 0, pretend = 0, frame = 0
@ frame_needed = 0, uses_anonymous_args = 0
@ link register save eliminated.
ldrb r3, [r0, #0] @ zero_extendqisi2
cmp r3, #0
bxeq lr
mov r2, #-536870912
add r2, r2, #49152
.L3:
str r3, [r2, #0]
ldrb r3, [r0, #1]! @ zero_extendqisi2
cmp r3, #0
bne .L3
bx lr
... which seems correct to me. (my build was from svn trunk, current date
20080211, unknow revision number [my build system got rid of .svn subdirs]).
No chance of a 4.2.x backport ? :-)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35141