llvm dev - Oct 2017 - EnableFastISel

Hi,

In SelectionDAGISel::SelectAllBasicBlocks

  if (TM.Options.EnableFastISel)
    FastIS = TLI->createFastISel(*FuncInfo, LibInfo);

followed by

  if (!FastIS) {
    LowerArguments(Fn);
  } else {
  
The above implies that implementing FastIS is optional.


In contrast to that, testing whether FastIS is actually been used is
done by testing if TM.Options.EnableFastISel is set.

For example in SelectionDAGISel::LowerArguments

    SDB->setValue(&Arg, Res);
    if (!TM.Options.EnableFastISel && Res.getOpcode() ==  
                                                   ISD::BUILD_PAIR) {
      if (LoadSDNode *LNode          
dyn_cast<LoadSDNode>(Res.getOperand(0).getNode()))
        if (FrameIndexSDNode *FI            
dyn_cast<FrameIndexSDNode>(LNode->getBasePtr().getNode()))
        FuncInfo->setArgumentFrameIndex(&Arg, FI->getIndex());
    }


Is it in BUG or am I missing something?

Thanks,
Yaniv

Not the right mailing list?

On Tue, 2017-10-24 at 00:55 +0300, Yaniv wrote:
> Hi,
> 
> In SelectionDAGISel::SelectAllBasicBlocks
> 
>   if (TM.Options.EnableFastISel)
>     FastIS = TLI->createFastISel(*FuncInfo, LibInfo);
> 
> followed by
> 
>   if (!FastIS) {
>     LowerArguments(Fn);
>   } else {
>   
> The above implies that implementing FastIS is optional.
> 
> 
> In contrast to that, testing whether FastIS is actually been used is
> done by testing if TM.Options.EnableFastISel is set.
> 
> For example in SelectionDAGISel::LowerArguments
> 
>     SDB->setValue(&Arg, Res);
>     if (!TM.Options.EnableFastISel && Res.getOpcode() ==  
>                                                    ISD::BUILD_PAIR) {
>       if (LoadSDNode *LNode >          
dyn_cast<LoadSDNode>(Res.getOperand(0).getNode()))
>         if (FrameIndexSDNode *FI >            
dyn_cast<FrameIndexSDNode>(LNode-
> >getBasePtr().getNode()))
>         FuncInfo->setArgumentFrameIndex(&Arg, FI->getIndex());
>     }
> 
> 
> Is it in BUG or am I missing something?
> 
> Thanks,
> Yaniv

On 10/30/2017 2:50 PM, Yaniv via llvm-dev wrote:
> Not the right mailing list?
This is the right mailing list; sometimes people just lose track of an 
email.

Looking briefly at your question, yes, I agree it's a bug, but probably 
not one which has much impact, given the code it controls.

-Eli
>
> On Tue, 2017-10-24 at 00:55 +0300, Yaniv wrote:
>> Hi,
>>
>> In SelectionDAGISel::SelectAllBasicBlocks
>>
>>    if (TM.Options.EnableFastISel)
>>      FastIS = TLI->createFastISel(*FuncInfo, LibInfo);
>>
>> followed by
>>
>>    if (!FastIS) {
>>      LowerArguments(Fn);
>>    } else {
>>    
>> The above implies that implementing FastIS is optional.
>>
>>
>> In contrast to that, testing whether FastIS is actually been used is
>> done by testing if TM.Options.EnableFastISel is set.
>>
>> For example in SelectionDAGISel::LowerArguments
>>
>>      SDB->setValue(&Arg, Res);
>>      if (!TM.Options.EnableFastISel && Res.getOpcode()
=>>                                                     ISD::BUILD_PAIR) {
>>        if (LoadSDNode *LNode >>           
dyn_cast<LoadSDNode>(Res.getOperand(0).getNode()))
>>          if (FrameIndexSDNode *FI >>             
dyn_cast<FrameIndexSDNode>(LNode-
>>> getBasePtr().getNode()))
>>          FuncInfo->setArgumentFrameIndex(&Arg,
FI->getIndex());
>>      }
>>
>>
>> Is it in BUG or am I missing something?
>>
>> Thanks,
>> Yaniv
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> llvm-dev at lists.llvm.org
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