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Re: [PATCH] Fix simplify_relational_operation_1 to avoid creating invalid rtl sharing (PR debug/42662)

From: Jeff Law <law at redhat dot com>
To: Jakub Jelinek <jakub at redhat dot com>
Cc: gcc-patches at gcc dot gnu dot org
Date: Mon, 11 Jan 2010 09:29:10 -0700
Subject: Re: [PATCH] Fix simplify_relational_operation_1 to avoid creating invalid rtl sharing (PR debug/42662)
References: <20100111160758.GY16723@hs20-bc2-1.build.redhat.com>

On 01/11/10 09:07, Jakub Jelinek wrote:

Hi!

As shown on the testcase below, simplify_relational_operation_1
when canonicalizing (ltu (plus x y) y) can create invalid rtl sharing,
if x can't be shared, because it uses op0's first operand twice in the
generated rtl.
Similar place where we optimize floating 2*x into x+x is handled properly
(calls copy_rtx).  I couldn't find other similar issues during quick
skimming of simplify-rtx.c.

Fixed thusly, bootstrapped/regtested on x86_64-linux.
Ok for trunk?  What about 4.4 where this bug is latent?

2010-01-11 Jakub Jelinek<jakub@redhat.com>

	PR debug/42662
	* simplify-rtx.c (simplify_relational_operation_1): Avoid invalid rtx
	sharing when canonicalizing ({lt,ge}u (plus a b) b).

* gcc.dg/pr42662.c: New test.

OK for trunk. I think it's ok for 4.4 as well, but give whomever owns that branch some time to chime in.

jeff

References:
- [PATCH] Fix simplify_relational_operation_1 to avoid creating invalid rtl sharing (PR debug/42662)
  - From: Jakub Jelinek

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