[llvm-dev] EnableFastISel

[Friedman, Eli via llvm-dev]

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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