[PATCH] Fix PR23603, teach VRP about comparison/truthop result ranges

[Richard Guenther]

This fixes VRP to fall back to [0,1] instead of varying where a truthvalue
is the result and the TYPE_PRECISION covers more than [0,1].

It also adjusts vrp_visit_phi_node to not so conservatively fall back
to +INF/-INF if all PHI arguments visited are constant (this fixes the
second testcase).

Bootstrapped and tested on x86_64-unknown-linux-gnu.

Will apply to mainline tomorrow.

Richard.

2007-01-07  Richard Guenther  <rguenther@suse.de>

        PR tree-optimization/23603
        * tree-vrp.c (set_value_range_to_truthvalue): New function.
        (extract_range_from_binary): Fall back to truthvalue instead of
        varying for TRUTH_*_EXPR.
        (extract_range_from_comparison): Fall back to truthvalue instead of
        varying.
        (vrp_visit_phi_node): Don't adjust new range bounds to +INF/-INF
        if all visited PHI values were constant.

        * gcc.dg/tree-ssa/vrp31.c: New testcase.
        * gcc.dg/tree-ssa/vrp32.c: Likewise.
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