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Re: [PATCH] Optimize BIT_AND_EXPRs for UBSAN_OBJECT_SIZE

From: Jeff Law <law at redhat dot com>
To: Marek Polacek <polacek at redhat dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Jakub Jelinek <jakub at redhat dot com>
Date: Mon, 03 Nov 2014 15:07:13 -0700
Subject: Re: [PATCH] Optimize BIT_AND_EXPRs for UBSAN_OBJECT_SIZE
Authentication-results: sourceware.org; auth=none
References: <20141103204705 dot GQ20462 at redhat dot com>

On 11/03/14 13:47, Marek Polacek wrote:

We don't emit UBSAN_BOUNDS checks in case we can at compile-time
prove that the array access is fine.  Also if we have [i & CST],
where CST is <= bound_of_the_array, we know we're fine as well.

But we don't have similar BIT_AND_EXPR check for UBSAN_OBJECT_SIZE
which is what this patch attempts to add.
(This is unrelated to the UBSAN_NULL optimization I posted earlier
today.)

Bootstrap-ubsan/regtest passed on x86_64-linux, ok for trunk?

2014-11-03  Marek Polacek  <polacek@redhat.com>

	* ubsan.c (instrument_object_size): Optimize [x & CST] array accesses.
testsuite/
	* c-c++-common/ubsan/object-size-10.c: New test.

OK.
jeff

References:
- [PATCH] Optimize BIT_AND_EXPRs for UBSAN_OBJECT_SIZE
  - From: Marek Polacek

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