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Triple Yang

2012-Dec-02 04:44 UTC

[LLVMdev] Splitting a load with 2 consumers into 2 loads.

Hi, Joe.

I am sorry I did not catch your point. Can you provide more details?

Since SDValue/SDNode can be used multiple times, why would you want to
create two identical objects
instead of reference to the same one?

2012/12/2 Joseph Pusdesris <joe at pusdesris.com>:> Yes, changing parameters will create a new Node, but is there some way I
can
> force a new node with the same parameters?
> -Joe
>
>
> On Sat, Dec 1, 2012 at 10:57 PM, Triple Yang <triple.yang at
gmail.com> wrote:
>>
>> Hi, Joseph, I guess getLoad() will either search an existed SDValue
>> *OR* create a new one for a non-existed one depending on real
>> parameters.
>>
>> Since you use exactly the same attributes dupVal/dupNode have, no
>> doubt getLoad() return the old one.
>>
>> I am not sure it's *volatile* that let you get a new result, you
might
>> want to try change some other parameters and check what it turns out.
>>
>> Regards.
>>
>> 2012/12/2 Joseph Pusdesris <joe at pusdesris.com>
>> >
>> > So I think I have made some progress.
>> > SDValue dupVal  = consumer->getOperand(OpNo);
>> > LoadSDNode *dupNode = (LoadSDNode*) dupVal.getNode();
>> >
>> > SDValue newLoad = CurDAG->getLoad(dupVal.getValueType(),
>> > dupVal.getDebugLoc(),
>> >                                dupVal.getOperand(0),
>> > dupVal.getOperand(1),
>> >                                dupNode->getPointerInfo(),
>> >                                dupNode->isVolatile(),
>> > dupNode->isNonTemporal(),
>> >                                dupNode->isInvariant(),
>> > dupNode->getAlignment(),
>> >                                dupNode->getTBAAInfo(),
>> > dupNode->getRanges());
>> > However, my problem now is that it will re-use the same load
still.  If
>> > I change something, like setting volatile to true for example, it
will
>> > create a new node, but otherwise it will not.  Any ideas?
>> > -Joe
>> >
>> >
>> > On Fri, Nov 30, 2012 at 9:55 PM, Joseph Pusdesris <joe at
pusdesris.com>
>> > wrote:
>> >>
>> >> Hi, I am writing an llvm target and I need both loads for isel
reasons,
>> >> but I am struggling to find the right way.  I have been trying
to use
>> >> DAG.getLoad() to make a copy, then just change the operand in
the consumers,
>> >> but I cannot seem to get all of the arguments needed for that
function in
>> >> order to make the copy.  Any help would be great, thanks!
>> >> -Joe
>> >
>> >
>> >
>> > _______________________________________________
>> > LLVM Developers mailing list
>> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >
>>
>>
>>
>> --
>> 杨勇勇 (Yang Yongyong)
>
>


-- 
杨勇勇 (Yang Yongyong)

Joseph Pusdesris

2012-Dec-02 06:20 UTC

head link

[LLVMdev] Splitting a load with 2 consumers into 2 loads.

I am writing a target for an odd cisc-like architecture which has no
support for keeping most values in registers.  As such, memory-memory
operations are needed, but for isel to generate a memory-memory the pattern
must be of the form (store (op (load) (load))).

Let's use a simple example to show how this can be problematic:
  %0 = load i32* %a.addr, align 4
  store i32 %0, i32* %other, align 4
  %1 = load i32* %b.addr, align 4
  %add = add i32 %0, %1
----
In this example, the (store (load)) pair -- the first two lines -- will be
matched by isel as a MOVmm.  This will be problematic for the add though,
since the load SDNode will be gone, making that part of the DAG no longer
of the form (add (load) (load)).  To counteract this, I would create 2 load
SDNodes so that both of these patterns can be satisfied.  Does this make
sense?
-Joe




On Sat, Dec 1, 2012 at 11:44 PM, Triple Yang <triple.yang at gmail.com>
wrote:
> Hi, Joe.
>
> I am sorry I did not catch your point. Can you provide more details?
>
> Since SDValue/SDNode can be used multiple times, why would you want to
> create two identical objects
> instead of reference to the same one?
>
> 2012/12/2 Joseph Pusdesris <joe at pusdesris.com>:
> > Yes, changing parameters will create a new Node, but is there some way
I
> can
> > force a new node with the same parameters?
> > -Joe
> >
> >
> > On Sat, Dec 1, 2012 at 10:57 PM, Triple Yang <triple.yang at
gmail.com>
> wrote:
> >>
> >> Hi, Joseph, I guess getLoad() will either search an existed
SDValue
> >> *OR* create a new one for a non-existed one depending on real
> >> parameters.
> >>
> >> Since you use exactly the same attributes dupVal/dupNode have, no
> >> doubt getLoad() return the old one.
> >>
> >> I am not sure it's *volatile* that let you get a new result,
you might
> >> want to try change some other parameters and check what it turns
out.
> >>
> >> Regards.
> >>
> >> 2012/12/2 Joseph Pusdesris <joe at pusdesris.com>
> >> >
> >> > So I think I have made some progress.
> >> > SDValue dupVal  = consumer->getOperand(OpNo);
> >> > LoadSDNode *dupNode = (LoadSDNode*) dupVal.getNode();
> >> >
> >> > SDValue newLoad = CurDAG->getLoad(dupVal.getValueType(),
> >> > dupVal.getDebugLoc(),
> >> >                                dupVal.getOperand(0),
> >> > dupVal.getOperand(1),
> >> >                                dupNode->getPointerInfo(),
> >> >                                dupNode->isVolatile(),
> >> > dupNode->isNonTemporal(),
> >> >                                dupNode->isInvariant(),
> >> > dupNode->getAlignment(),
> >> >                                dupNode->getTBAAInfo(),
> >> > dupNode->getRanges());
> >> > However, my problem now is that it will re-use the same load
still.
>  If
> >> > I change something, like setting volatile to true for
example, it will
> >> > create a new node, but otherwise it will not.  Any ideas?
> >> > -Joe
> >> >
> >> >
> >> > On Fri, Nov 30, 2012 at 9:55 PM, Joseph Pusdesris <joe at
pusdesris.com>
> >> > wrote:
> >> >>
> >> >> Hi, I am writing an llvm target and I need both loads for
isel
> reasons,
> >> >> but I am struggling to find the right way.  I have been
trying to use
> >> >> DAG.getLoad() to make a copy, then just change the
operand in the
> consumers,
> >> >> but I cannot seem to get all of the arguments needed for
that
> function in
> >> >> order to make the copy.  Any help would be great, thanks!
> >> >> -Joe
> >> >
> >> >
> >> >
> >> > _______________________________________________
> >> > LLVM Developers mailing list
> >> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >> >
> >>
> >>
> >>
> >> --
> >> 杨勇勇 (Yang Yongyong)
> >
> >
>
>
>
> --
> 杨勇勇 (Yang Yongyong)
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Triple Yang

2012-Dec-02 17:06 UTC

head link

[LLVMdev] Splitting a load with 2 consumers into 2 loads.

OK, I get it.

The essence of this problem is that a node can be covered exactly and
just once but its result can be referred multiple times for a tree
pattern matching isel. So to duplicate a load node (only if we can!)
is convenient to conquer that case.

The truth is, in pattern (add (load) (load)), source operands are
memory addresses, and thus it can be treated         as (addmm
address, address). Here is an alternative you can take into
consideration: defining new node (like addmm, similiar with movmm) to
specify matching patterns for isel.

Regards.

2012/12/2 Joseph Pusdesris <joe at pusdesris.com>:> I am writing a target for an odd cisc-like architecture which has no
support
> for keeping most values in registers.  As such, memory-memory operations
are
> needed, but for isel to generate a memory-memory the pattern must be of the
> form (store (op (load) (load))).
>
> Let's use a simple example to show how this can be problematic:
>   %0 = load i32* %a.addr, align 4
>   store i32 %0, i32* %other, align 4
>   %1 = load i32* %b.addr, align 4
>   %add = add i32 %0, %1
> ----
> In this example, the (store (load)) pair -- the first two lines -- will be
> matched by isel as a MOVmm.  This will be problematic for the add though,
> since the load SDNode will be gone, making that part of the DAG no longer
of
> the form (add (load) (load)).  To counteract this, I would create 2 load
> SDNodes so that both of these patterns can be satisfied.  Does this make
> sense?
> -Joe
>
>
>
>
> On Sat, Dec 1, 2012 at 11:44 PM, Triple Yang <triple.yang at
gmail.com> wrote:
>>
>> Hi, Joe.
>>
>> I am sorry I did not catch your point. Can you provide more details?
>>
>> Since SDValue/SDNode can be used multiple times, why would you want to
>> create two identical objects
>> instead of reference to the same one?
>>
>> 2012/12/2 Joseph Pusdesris <joe at pusdesris.com>:
>> > Yes, changing parameters will create a new Node, but is there some
way I
>> > can
>> > force a new node with the same parameters?
>> > -Joe
>> >
>> >
>> > On Sat, Dec 1, 2012 at 10:57 PM, Triple Yang <triple.yang at
gmail.com>
>> > wrote:
>> >>
>> >> Hi, Joseph, I guess getLoad() will either search an existed
SDValue
>> >> *OR* create a new one for a non-existed one depending on real
>> >> parameters.
>> >>
>> >> Since you use exactly the same attributes dupVal/dupNode have,
no
>> >> doubt getLoad() return the old one.
>> >>
>> >> I am not sure it's *volatile* that let you get a new
result, you might
>> >> want to try change some other parameters and check what it
turns out.
>> >>
>> >> Regards.
>> >>
>> >> 2012/12/2 Joseph Pusdesris <joe at pusdesris.com>
>> >> >
>> >> > So I think I have made some progress.
>> >> > SDValue dupVal  = consumer->getOperand(OpNo);
>> >> > LoadSDNode *dupNode = (LoadSDNode*) dupVal.getNode();
>> >> >
>> >> > SDValue newLoad =
CurDAG->getLoad(dupVal.getValueType(),
>> >> > dupVal.getDebugLoc(),
>> >> >                                dupVal.getOperand(0),
>> >> > dupVal.getOperand(1),
>> >> >                               
dupNode->getPointerInfo(),
>> >> >                                dupNode->isVolatile(),
>> >> > dupNode->isNonTemporal(),
>> >> >                                dupNode->isInvariant(),
>> >> > dupNode->getAlignment(),
>> >> >                                dupNode->getTBAAInfo(),
>> >> > dupNode->getRanges());
>> >> > However, my problem now is that it will re-use the same
load still.
>> >> > If
>> >> > I change something, like setting volatile to true for
example, it
>> >> > will
>> >> > create a new node, but otherwise it will not.  Any ideas?
>> >> > -Joe
>> >> >
>> >> >
>> >> > On Fri, Nov 30, 2012 at 9:55 PM, Joseph Pusdesris <joe
at pusdesris.com>
>> >> > wrote:
>> >> >>
>> >> >> Hi, I am writing an llvm target and I need both loads
for isel
>> >> >> reasons,
>> >> >> but I am struggling to find the right way.  I have
been trying to
>> >> >> use
>> >> >> DAG.getLoad() to make a copy, then just change the
operand in the
>> >> >> consumers,
>> >> >> but I cannot seem to get all of the arguments needed
for that
>> >> >> function in
>> >> >> order to make the copy.  Any help would be great,
thanks!
>> >> >> -Joe
>> >> >
>> >> >
>> >> >
>> >> > _______________________________________________
>> >> > LLVM Developers mailing list
>> >> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> >> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>> >> >
>> >>
>> >>
>> >>
>> >> --
>> >> 杨勇勇 (Yang Yongyong)
>> >
>> >
>>
>>
>>
>> --
>> 杨勇勇 (Yang Yongyong)
>
>


-- 
杨勇勇 (Yang Yongyong)

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