Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ?

[Paul Koning]

On Nov 8, 2010, at 6:20 AM, Richard Guenther wrote:

> On Mon, Nov 8, 2010 at 12:20 PM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
>> Richard Guenther <richard.guenther@xxxxxxxxx> writes:
>> 
>>> On Mon, Nov 8, 2010 at 12:03 AM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
>>>> Andreas Schwab <schwab@xxxxxxxxxxxxxx> writes:
>>>>> 
>>>>> The asm fails to mention that it modifies *regs.
>>>> 
>>>> It has a memory clobber, that should be enough, no?
>>> 
>>> No.  A memory clobber does not cover automatic storage.
>> 
>> That's a separate problem.
>> 
>>> Btw, I can't see a testcase anywhere so I just assume Andreas got
>>> it right as usual.
>> 
>> An asm with live inputs and outputs should never be optimized
>> way. If 4.5.1 started doing that it's seriously broken.
> 
> Please provide a testcase, such asms can be optimized if the
> outputs are dead.

I don't know about 4.5, but I noticed that with 4.6 (trunk), testcasese like gcc.c-torture/compile/20000804-1.c optimize away the asm and all the operand generation except for -O0.

	paul

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