[PATCH take 2] Fold bswap32(x) != 0 to x != 0 (and related transforms)

[Roger Sayle]

My apologies for the short delay.  Thanks for explaining why these
transforms
don't usually require explicit tests for side-effects (but occasionally do).
This does simplify things; please find attached the shorter revised patch.

This patch has been retested on x86_64-pc-linux-gnu with a make bootstrap
and make -k check with no new failures.  Ok for mainline?

2010-07-24  Roger Sayle  <roger@nextmovesoftware.com>
	    Marc Glisse  <marc.glisse@inria.fr>

gcc/ChangeLog
	* match.pd (rotate): Simplify equality/inequality of rotations.
	(bswap): Simplify equality/inequality tests of byte swapping.

gcc/testsuite/ChangeLog
	* gcc.dg/fold-eqrotate-1.c: New test case.
	* gcc.dg/fold-eqbswap-1.c: New test case.

Roger
--

-----Original Message-----
From: Marc Glisse <marc.glisse@inria.fr> 
Sent: 18 July 2021 23:03
To: Roger Sayle <roger@nextmovesoftware.com>
Cc: 'GCC Patches' <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] Fold bswap32(x) != 0 to x != 0 (and related transforms)

On Sun, 18 Jul 2021, Roger Sayle wrote:

> +    (if (GIMPLE || !TREE_SIDE_EFFECTS (@0))

I don't think you need to worry about that, the general genmatch machinery
is already supposed to take care of it. All the existing cases in match.pd
are about cond_expr, where counting the occurrences of each @i is not
reliable.

--
Marc Glisse
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