On Mon, Jul 18, 2022 at 3:12 PM Segher Boessenkool
wrote:
>
> Assembler language is unforgiving. It isn't easy to write, and most
> mistakes will not be diagnosed. If the assmbler language makes it
> easier to read the code, that makes it more likely correct code will be
> written, and that corr
On Mon, Jul 18, 2022 at 12:06:52PM -0700, Linus Torvalds wrote:
> On Sun, Jul 17, 2022 at 9:41 PM Michael Ellerman wrote:
> > > li 4,254 #,
> >
> > Here we load 254 into r4, which is the 2nd parameter to memset (c).
>
> I love how even powerpc people know that "4" is bogus
On Sun, Jul 17, 2022 at 9:41 PM Michael Ellerman wrote:
>
> > li 4,254 #,
>
> Here we load 254 into r4, which is the 2nd parameter to memset (c).
I love how even powerpc people know that "4" is bogus, and have to
make it clear that it means "r4".
I don't understand why th
On Mon, Jul 18, 2022 at 01:52:38PM +1000, Michael Ellerman wrote:
> Segher Boessenkool writes:
> > Can't we simply have a small simple implementation of these functions in
> > arch/powerpc/boot/? This stuff is not performance-critical, and this is
> > not the first time we hit these problems.
>
From: Michael Ellerman
> Sent: 18 July 2022 05:41
...
> So we're memsetting all of args to 254, not zero.
>
> That's happening because allmodconfig with gcc 12 enables
> CONFIG_INIT_STACK_ALL_PATTERN, whereas gcc 11 doesn't.
I can't help feeling it would be better if that generated
a call to a me
Sudip Mukherjee writes:
> On Thu, Jul 14, 2022 at 9:55 AM Sudip Mukherjee (Codethink)
> wrote:
>>
>> Hi All,
>>
>> Not sure if it has been reported before but the latest mainline kernel
>> branch fails to build for powerpc allmodconfig with gcc-12 and the error is:
>>
>> Error: External symbol 'm
Segher Boessenkool writes:
> On Sun, Jul 17, 2022 at 07:44:22AM -0700, Linus Torvalds wrote:
>> On Sun, Jul 17, 2022 at 2:13 AM Sudip Mukherjee
>> wrote:
>> > I was trying to check it. With gcc-11 the assembly code generated is
>> > not using memset, but using __memset.
>> > But with gcc-12, I ca
On Sun, Jul 17, 2022 at 2:49 PM Segher Boessenkool
wrote:
>
> > I can *kind of* see the logic that when you do a whole struct
> > assignment, it turns into a "memcpy" without regard for volatile
> > members. You're not actually accessing the volatile members in some
> > particular order, so the st
On Sun, Jul 17, 2022 at 02:11:52PM -0700, Linus Torvalds wrote:
> On Sun, Jul 17, 2022 at 2:00 PM Segher Boessenkool
> wrote:
> > Calling mem* on a volatile object (or a struct containing one) is not
> > valid. I opened gcc.gnu.org/PR106335.
>
> Well, that very quickly got marked as a duplicate
On Sun, Jul 17, 2022 at 2:00 PM Segher Boessenkool
wrote:
>
> Calling mem* on a volatile object (or a struct containing one) is not
> valid. I opened gcc.gnu.org/PR106335.
Well, that very quickly got marked as a duplicate of a decade-old bug.
So I guess we shouldn't expect this to be fixed any
On Sun, Jul 17, 2022 at 01:29:07PM -0700, Linus Torvalds wrote:
> On Sun, Jul 17, 2022 at 1:25 PM Sudip Mukherjee
> wrote:
> >
> > And the generated assembly still has the memset for "struct prom_args".
>
> Strange. That smells like a compiler bug to me.
>
> But I can't read powerpc assembly cod
On Sun, Jul 17, 2022 at 1:38 PM Sudip Mukherjee
wrote:
>
> I have also tried adding volatile to all the members of that struct. :(
Can you read the code to figure otu what the memcpy is all about?
Or maybe there is something that disables 'volatile' with pre-processor hackery.
Because a compil
On Sun, Jul 17, 2022 at 9:29 PM Linus Torvalds
wrote:
>
> On Sun, Jul 17, 2022 at 1:25 PM Sudip Mukherjee
> wrote:
> >
> > And the generated assembly still has the memset for "struct prom_args".
>
> Strange. That smells like a compiler bug to me.
Both gcc-12 and clang gives this error.
>
> But
On Sun, Jul 17, 2022 at 1:25 PM Sudip Mukherjee
wrote:
>
> And the generated assembly still has the memset for "struct prom_args".
Strange. That smells like a compiler bug to me.
But I can't read powerpc assembly code - it's been too many years, and
even back when I did read it I hated how the r
On Sun, Jul 17, 2022 at 3:44 PM Linus Torvalds
wrote:
>
> On Sun, Jul 17, 2022 at 2:13 AM Sudip Mukherjee
> wrote:
> >
> > I was trying to check it. With gcc-11 the assembly code generated is
> > not using memset, but using __memset.
> > But with gcc-12, I can see the assembly code is using memse
On Sun, Jul 17, 2022 at 07:44:22AM -0700, Linus Torvalds wrote:
> On Sun, Jul 17, 2022 at 2:13 AM Sudip Mukherjee
> wrote:
> > I was trying to check it. With gcc-11 the assembly code generated is
> > not using memset, but using __memset.
> > But with gcc-12, I can see the assembly code is using me
On Sun, Jul 17, 2022 at 2:13 AM Sudip Mukherjee
wrote:
>
> I was trying to check it. With gcc-11 the assembly code generated is
> not using memset, but using __memset.
> But with gcc-12, I can see the assembly code is using memset. One
> example from the assembly:
You could try making the 'args'
On Thu, Jul 14, 2022 at 9:55 AM Sudip Mukherjee (Codethink)
wrote:
>
> Hi All,
>
> Not sure if it has been reported before but the latest mainline kernel
> branch fails to build for powerpc allmodconfig with gcc-12 and the error is:
>
> Error: External symbol 'memset' referenced from prom_init.c
>
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