Messages in this thread | | | From | Andreas Schwab <> | Subject | Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ? | Date | Sun, 07 Nov 2010 23:41:37 +0100 |
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Andi Kleen <andi@firstfloor.org> writes:
> Jim <jim876@xs4all.nl> writes: > >> After upgrading my Dell laptop, both OS+kernel the i8k interface was giving >> nonsensical output. As it turned out it's not the kernel but compiler >> upgrade which broke this. >> >> Guys at Archlinux have found the underlying cause (but don't seem to have >> submitted a patch yet): >> https://bbs.archlinux.org/viewtopic.php?pid=780692#p780692 >> gcc seems to optimize the assembly statements away. >> >> And indeed, applying this patch makes the i8k interface work again, >> i.e. replacing the asm(..) construct by asm volatile(..) > > The compiler really should not optimize the asm away, because > it has both input and output arguments which are later used. > "asm volatile" normally just means "don't move significantly"
The asm fails to mention that it modifies *regs.
Andreas.
-- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different."
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