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Re: [PATCH] simplify-rtx: Simplify sign_extend of lshiftrt to zero_extend (PR68330)
- From: Eric Botcazou <ebotcazou at adacore dot com>
- To: Segher Boessenkool <segher at kernel dot crashing dot org>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Mon, 16 Nov 2015 10:29:47 +0100
- Subject: Re: [PATCH] simplify-rtx: Simplify sign_extend of lshiftrt to zero_extend (PR68330)
- Authentication-results: sourceware.org; auth=none
- References: <821bd594c0c0593a61208d2968ff2e52960ece00 dot 1447553408 dot git dot segher at kernel dot crashing dot org>
> Since r230164, in PR68330 combine ends up with a sign_extend of an
> lshiftrt by some constant, and it does not know to morph that into a
> zero_extract (the extend will always extend with zeroes). I think
> it is best to let simplify-rtx always replace such a sign_extend by
> a zero_extend, after which everything works as expected.
Agreed.
> 2015-11-15 Segher Boessenkool <segher@kernel.crashing.org>
>
> PR rtl-optimization/68330
> * simplify-rtx.c (simplify_unary_operation_1): Simplify SIGN_EXTEND
> of LSHIFTRT by a non-zero constant integer.
OK, thanks.
--
Eric Botcazou