Patch for misleading comment in src/share/vm/opto/node.cpp

[Tom Rodriguez]

On Feb 24, 2009, at 12:32 AM, Christian Thalinger wrote:

> On Mon, 2009-02-23 at 11:15 -0800, Peter B. Kessler wrote:
>> Peter B. Kessler wrote:
>>> This comment is so wrong as almost to qualify as malicious.   
>>> Here's a
>>> patch that might help.
>>>
>>>     src/share/vm/opto/node.cpp
>>>
>>>     971 // If you modify the 'this' pointer's inputs, you must use  
>>> 'set_req' with
>>>     972 // def-use info.  If you are making a new Node (either as  
>>> the new root or
>>>     973 // some new internal piece) you must NOT use set_req with  
>>> def-use info.
>>>     974 // You can make a new Node with either 'new' or 'clone'.   
>>> In either case,
>>>     975 // def-use info is (correctly) not generated.

This piece isn't valid either.  There's no separate du argument to any  
of the set functions anymore.

tom

>>>
>>>     976 // Example: reshape "(X+3)+4" into "X+7":
>>>     977 //    set_req(1,in(1)->in(1) /* grab X */, du /* must use  
>>> DU on 'this' */);
>>>     978 //    set_req(2,phase->intcon(7),du);
>>>     979 //    return this;
>>> -    980 // Example: reshape "X*4" into "X<<1"
>>> -    981 //    return new (C,3) LShiftINode( in(1), phase- 
>>> >intcon(1) );
>>> +    980 // Example: reshape "X*4" into "X<<2"
>>> +    981 //    return new (C,3) LShiftINode( in(1), phase- 
>>> >intcon(2) );
>>>     982 //
>>>     983 // You must call 'phase->transform(X)' on any new Nodes X  
>>> you make, except
>>> -    984 // for the returned root node.  Example: reshape "X*31"  
>>> with "(X<<5)-1".
>>> -    985 //    Node *shift=phase->transform(new(C, 
>>> 3)LShiftINode(in(1),phase->intcon(5)));
>>> -    986 //    return new (C,3) AddINode(shift, phase->intcon(-1));
>>> +    984 // for the returned root node.  Example: reshape "X*31"  
>>> with "(X<<5)-X".
>>> +    985 //    Node *shift=phase->transform(new(C, 
>>> 3)LShiftINode(in(1),phase->intcon(5)));
>>> +    986 //    return new (C,3) SubINode(shift, phase- 
>>> >intcon(in(1)));
>>
>> This last line should probably be
>>
>> +    986 //    return new (C,3) SubINode(shift, in(1));
>>
>> but I admit I'm a noob in this part of the code.  (Which is why I  
>> was reading the comments. :-)
>
> I'm not an expert either but it looks good.  I'm adding this one to my
> typos-repository.  Thanks!
>
> -- Christian
>