Say you have a pointer:
int *p;
and an inline asm that writes to a block of memory
__asm__("\t0:\n"
"\tstr wzr, [%2, #4]!\n"
"\tsub %1, %1, #1\n"
"\tcbnz %1, 0b\n"
: "=m"(*p), "+r"(len) : "r"(p));
I presume this is wrong because *p only refers to p[0].
On Wed, Feb 26, 2014 at 11:32 AM, Andrew Haley wrote:
> Say you have a pointer:
>
> int *p;
>
> and an inline asm that writes to a block of memory
>
> __asm__("\t0:\n"
> "\tstr wzr, [%2, #4]!\n"
> "\tsub %1, %1, #1\n"
> "\tcbnz %1, 0b\n"
> : "=m"(*p), "+r"
On Tue, Feb 25, 2014 at 1:08 AM, Anthony Green wrote:
>
> Have you considered doing this through custom GNU linker relaxation
> work? I would try this before hacking away at the compiler.
>
> AG
>
>
This a very good idea indeed, I wasn't aware of this feature.
I will give it a try based on othe
On 02/26/2014 10:51 AM, Richard Biener wrote:
> But yes, technically you write p[0] here but as "m" merely builds
> an address to the memory I'd say that we have to treat any "m"
> operand as possibly reading from / writing to / clobbering the
> whole object that can be refered to using that addres
On Wed, Feb 26, 2014 at 12:10 PM, Andrew Haley wrote:
> On 02/26/2014 10:51 AM, Richard Biener wrote:
>> But yes, technically you write p[0] here but as "m" merely builds
>> an address to the memory I'd say that we have to treat any "m"
>> operand as possibly reading from / writing to / clobbering
On 02/26/2014 12:24 PM, Richard Biener wrote:
> An additional question that immediately pops up here is that
> of TBAA - may we use the alias-set of the memory reference
> to disambiguate other loads/stores against the asm?
I would certainly hope so: I don't think the rule here should be any
diffe
On Fri, 2014-02-21 at 11:13 -0800, Paul E. McKenney wrote:
> On Fri, Feb 21, 2014 at 07:35:37PM +0100, Michael Matz wrote:
> > Hi,
> >
> > On Thu, 20 Feb 2014, Linus Torvalds wrote:
> >
> > > But I'm pretty sure that any compiler guy must *hate* that current odd
> > > dependency-generation part,
On Fri, 2014-02-21 at 22:10 +, Joseph S. Myers wrote:
> On Fri, 21 Feb 2014, Paul E. McKenney wrote:
>
> > This needs to be as follows:
> >
> > [[carries_dependency]] int getzero(int i [[carries_dependency]])
> > {
> > return i - i;
> > }
> >
> > Otherwise dependencies won't get carried
Hi,
On Wed, 26 Feb 2014, Richard Biener wrote:
> > "\tstr wzr, [%2, #4]!\n"
> > "\tsub %1, %1, #1\n"
> > "\tcbnz %1, 0b\n"
> > : "=m"(*p), "+r"(len) : "r"(p));
> >
> > I presume this is wrong because *p only refers to p[0]. Is it
> > possible to tell GCC t
Michael Matz writes:
> On Wed, 26 Feb 2014, Richard Biener wrote:
>> > "\tstr wzr, [%2, #4]!\n"
>> > "\tsub %1, %1, #1\n"
>> > "\tcbnz %1, 0b\n"
>> > : "=m"(*p), "+r"(len) : "r"(p));
>> >
>> > I presume this is wrong because *p only refers to p[0]. Is it
>>
FWIW:
> __asm__("\t0:\n"
> "\tstr wzr, [%2, #4]!\n"
> "\tsub %1, %1, #1\n"
> "\tcbnz %1, 0b\n"
> : "=m"(*p), "+r"(len) : "r"(p));
"+r"(p) as well, you're modifying %2.
Cheers,
Segher
On 02/26/2014 04:43 PM, Segher Boessenkool wrote:
> "+r"(p) as well, you're modifying %2.
Yes, yes, OK. :-)
Andrew.
On Mon, 2014-02-24 at 09:38 -0800, Linus Torvalds wrote:
> On Mon, Feb 24, 2014 at 8:55 AM, Michael Matz wrote:
> >
> > So, let me try to poke holes into your definition or increase my
> > understanding :) . You said "chain of pointers"(dereferences I assume),
> > e.g. if p is result of consume l
On Mon, 2014-02-24 at 09:28 -0800, Paul E. McKenney wrote:
> On Mon, Feb 24, 2014 at 05:55:50PM +0100, Michael Matz wrote:
> > Hi,
> >
> > On Mon, 24 Feb 2014, Linus Torvalds wrote:
> >
> > > > To me that reads like
> > > >
> > > > int i;
> > > > int *q = &i;
> > > > int **p = &q;
> > > >
>
On Wed, Feb 26, 2014 at 02:04:30PM +0100, Torvald Riegel wrote:
> xagsmtp2.20140226130517.3...@vmsdvma.vnet.ibm.com
> X-Xagent-Gateway: vmsdvma.vnet.ibm.com (XAGSMTP2 at VMSDVMA)
>
> On Fri, 2014-02-21 at 11:13 -0800, Paul E. McKenney wrote:
> > On Fri, Feb 21, 2014 at 07:35:37PM +0100, Michael Ma
On Wed, 26 Feb 2014, Torvald Riegel wrote:
> On Fri, 2014-02-21 at 22:10 +, Joseph S. Myers wrote:
> > On Fri, 21 Feb 2014, Paul E. McKenney wrote:
> >
> > > This needs to be as follows:
> > >
> > > [[carries_dependency]] int getzero(int i [[carries_dependency]])
> > > {
> > > return i - i
On Wed, 2014-02-26 at 18:43 +, Joseph S. Myers wrote:
> On Wed, 26 Feb 2014, Torvald Riegel wrote:
>
> > On Fri, 2014-02-21 at 22:10 +, Joseph S. Myers wrote:
> > > On Fri, 21 Feb 2014, Paul E. McKenney wrote:
> > >
> > > > This needs to be as follows:
> > > >
> > > > [[carries_dependenc
Hello,
I'm wondering if it's a good idea to turn on some warnings by default
(or even promote them to error), such as -Wreturn-type on C. This
would help programmers to avoid some mistakes.
Regards,
Mingjie
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