[llvm-commits] [llvm] r139136 - /llvm/trunk/lib/Analysis/ScalarEvolution.cpp

[Nick Lewycky]

Eli Friedman wrote:
> On Mon, Sep 5, 2011 at 11:39 PM, Nick Lewycky<nicholas at mxc.ca>  wrote:
>> Author: nicholas
>> Date: Tue Sep  6 01:39:54 2011
>> New Revision: 139136
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=139136&view=rev
>> Log:
>> Nope! I had it right the first time. Revert the operative part of r139135 and
>> add more showing of my work.
>
> Commit message not consistent with the commit.

Thanks Eli!

Nick

>
> -Eli
>
>> Modified:
>>     llvm/trunk/lib/Analysis/ScalarEvolution.cpp
>>
>> Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=139136&r1=139135&r2=139136&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
>> +++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Tue Sep  6 01:39:54 2011
>> @@ -652,7 +652,7 @@
>>   /// Assume, K>  0.
>>   static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
>>                                         ScalarEvolution&SE,
>> -                                       Type* ResultTy) {
>> +                                       Type *ResultTy) {
>>    // Handle the simplest case efficiently.
>>    if (K == 1)
>>      return SE.getTruncateOrZeroExtend(It, ResultTy);
>> @@ -1976,12 +1976,15 @@
>>           OtherIdx<  Ops.size()&&  isa<SCEVAddRecExpr>(Ops[OtherIdx]);
>>           ++OtherIdx)
>>        if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
>> -        // {A,+,B}<L>  * {C,+,D}<L>    -->    {A*C,+,A*D + B*C - B*D,+,2*B*D}<L>
>> +        // {A,+,B}<L>  * {C,+,D}<L>    -->    {A*C,+,A*D + B*C + B*D,+,2*B*D}<L>
>>          //
>> -        // For reference, given that {X,+,Y,+,Z} = x + y*It + z*It^2 then
>> -        // X = x, Y = y-z, Z = 2z.
>> +        // {A,+,B} * {C,+,D} = A+It*B * C+It*D = A*C + (A*D + B*C)*It + B*D*It^2
>> +        // Given an equation of the form x + y*It + z*It^2 (above), we want to
>> +        // express it in terms of {X,+,Y,+,Z}.
>> +        // {X,+,Y,+,Z} = X + Y*It + Z*(It^2 - It)/2.
>> +        // Rearranging, X = x, Y = x+y, Z = 2z.
>>          //
>> -        // x = A*C, y = (A*D + B*C), z = B*D
>> +        // x = A*C, y = (A*D + B*C), z = B*D.
>>          // Therefore X = A*C, Y = (A*D + B*C) - B*D and Z = 2*B*D.
>>          for (; OtherIdx != Ops.size()&&  isa<SCEVAddRecExpr>(Ops[OtherIdx]);
>>               ++OtherIdx)
>>
>>
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>