Re: [PATCH] add VRP for bitwise OR and AND

["Richard Guenther" <richard dot guenther at gmail dot com>]

On 8/7/06, Daniel Berlin <dannyb@google.com> wrote:
> Denis Vlasenko wrote:
> > This patch adds value range propagation for (a&b), (a|b) operations.
> >
> > tree-vrp.c.diff is the patch itself, test_vrp.c is a test program.
> >
> > Differences in *.vrp (-fdump-tree-vrp output) and assembly generated
> > with stock 4.1.1 and with patched one out of test program test_vrp.c
> > are below the sig.
> >
> > I am not familiar with gcc internals, so please review carefully before
> > applying. For example, I construct integer contants like this:
> >
> >   tmp = build_int_cst (NULL_TREE, 1);
> >
> > while Andrew Pinski does it like this:
> >
> >   max = build_int_cst (TREE_TYPE (expr), 1);
>
> Both of you are wrong for the specific case of "1", it should be
> integer_one_node.  Zero should be integer_zero_node.
>
> Other than that, if you pass NULL as the type, it will assume you mean
> "integer_type_node".
>
> When working with oring/etc where it may matter what the size of the
> type of the variable is, you should use the type of the original operand.
>
> If it doesn't matter, feel free to pass NULL.

(I didn't look at the patch)
You should always use build_int_cst (whatever-type-you-need, 1) instead
of integer_one_node or integer_zero_node.  At least once you start feeding
this node to helpers in the middle-end.

Richard.