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Avoid generating useless range info

From: Aldy Hernandez <aldyh at redhat dot com>
To: Richard Biener <richard dot guenther at gmail dot com>
Cc: Andrew MacLeod <amacleod at redhat dot com>, gcc-patches <gcc-patches at gcc dot gnu dot org>
Date: Wed, 14 Jun 2017 12:41:52 -0400
Subject: Avoid generating useless range info
Authentication-results: sourceware.org; auth=none

Hi!

As discovered in my range class work, we seem to generate a significantamount of useless range info out of VRP.

Is there any reason why we can't avoid generating any range info thatspans the entire domain, and yet contains nothing in the non-zero bitmask?

The attached patch passes bootstrap, and the one regression it causes isbecause now the -Walloca-larger-than= pass is better able to determinethat there is no range information at all, and the testcase isunbounded. So...win, win.


OK for trunk?

Aldy

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