[Bug tree-optimization/31136] [4.2 Regression] FRE ignores bit-field truncation (C and C++ front-end don't produce bit-field truncation

[Andrew Pinski]

On 3/23/07, Andrew Pinski <pinskia@gmail.com> wrote:
> On 23 Mar 2007 05:01:00 -0000, spark at gcc dot gnu dot org
> <gcc-bugzilla@gcc.gnu.org> wrote:
> > The problematic STRIP_SIGN_NOPS() call is from fold_unary()
> > which is called from try_combine_conversion() in tree-ssa-pre.c.
> >
> > STRIP_SIGN_NOPS() is called with the expression:
>
> No, STRIP_SIGN_NOPS is correct, just fold_unary is incorrect in its
> folding.  It should have called fold_convert on the expression if the
> types are different and it is a constant.

Ok, the real issue is that we call fold with
NOP_EXPR<NOP_EXPR<INTEGER_CST>> instead of just NOP_EXPR<INTEGER_CST>
so you have to figure out where we should fold the first NOP_EXPR
instead of that patch.

-- Pinski