Simplify using context in loop-iv

[Paulo Matos <pmatos at broadcom dot com>]

Hello,

This is a followup of 
http://gcc.gnu.org/ml/gcc/2014-01/msg00120.html
and
http://gcc.gnu.org/ml/gcc/2014-01/msg00055.html

This is a slightly long patch that attempts to simplify the niter and infinite expressions by recursively looking through the dominant basic blocks for register definitions, replacing them in the original expressions and simplifying the expression with simplify-rtx.

It allows GCC to generate a lot more zero overhead loops by finding much better bounds to loops or discovering that infinite loops are actually not so.

I would like to have some comments on the patch and its possible integration into upstream (I guess it can only go upstream once 4.9 is released, right?).

I bootstrapped and tested x86_64-unknown-linux-gnu with no regressions.

Thanks,

Paulo Matos

Attachment: simplify-using-context.patch
Description: simplify-using-context.patch