[PATCH] Fix forwprop pattern (T)(P + A) - (T)P -> (T)A, Part 2

[Bernd Edlinger]

Hi,

this is part 2 of my patch, which uses the undefined behaviour, and emits a 
strict overflow warning.
This fixes gnat.dg/opt37.adb again.

The diff is relative to part 1: 
https://gcc.gnu.org/ml/gcc-patches/2014-06/msg01891.html


Boot-strapped and regression-tested on x86_64-linux-gnu.

OK for trunk?


Thanks
Bernd.
                                          
2014-06-25  Bernd Edlinger  <bernd.edlin...@hotmail.de>

        * tree-ssa-forwprop.c (associate_plusminus): For widening conversions
        check for undefined overflow in (T)(P + A) - (T)P -> (T)A.
        Issue a strict overflow warning if appropriate.

patch-forwprop2.diff
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