[PATCH][Review Requested][Compilation Time] Calculate hash value and equality comparison within SCEV node itself

[Nick Lewycky]

Murali, Sriram wrote:
> SCEV is currently implemented as a FoldingSetNode to calculate the
> hashing value and for equality comparison. This causes some performance
> loss. This patch aims at improving the compilation time performance by
> implementing the hashing and equality comparison within SCEV class
> instead of inheriting FoldingSetNode. The compilation performance gain
> for this particular refactoring is around 2%.

What is it about FoldingSet that causes a performance loss? It should 
not. I want to understand this. :)

Nick

> This patch is part of a series of compile time improvements. Although
> these were originally produced by our colleague Wan Xiaofei, our team
> consisting of tyler.nowicki at intel.com <mailto:tyler.nowicki at intel.com>;
> preston.gurd at intel.com <mailto:preston.gurd at intel.com>; and
> sriram.murali at intel.com <mailto:sriram.murali at intel.com>, are assuming
> all responsibility for this work.