[llvm-commits] [llvm] r141161 - /llvm/trunk/lib/Analysis/ScalarEvolution.cpp

[Nick Lewycky]

On 10/04/2011 08:25 PM, Andrew Trick wrote:
> Author: atrick
> Date: Tue Oct  4 22:25:31 2011
> New Revision: 141161
>
> URL: http://llvm.org/viewvc/llvm-project?rev=141161&view=rev
> Log:
> Avoid exponential recursion in SCEV getConstantEvolvingPHI and EvaluateExpression.
>
> Note to compiler writers: never recurse on multiple instruction
> operands without memoization.
> Fixes rdar://10187945. Was taking 45s, now taking 5ms.

Ugh. Sorry for adding this, I really didn't think this would be a 
problem in practice. Thanks for handling the fallout! Feel free to ask 
me to clean up my own performance problems too, if you like :)

Nick