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Re: GCC 4.6 is inserting unnecessary MOVAPS instructions for SSE intrinsics

From: Marc Glisse <marc dot glisse at inria dot fr>
To: Leith Bade <leith at leithalweapon dot geek dot nz>
Cc: gcc <gcc at gcc dot gnu dot org>
Date: Wed, 23 Nov 2011 12:13:03 +0100 (CET)
Subject: Re: GCC 4.6 is inserting unnecessary MOVAPS instructions for SSE intrinsics
References: <CAPDEroVX3h44LKfsrPWqvyFaP8ngoOHWbwtM7Me3cHQ3x+-n=g@mail.gmail.com>
Reply-to: gcc <gcc at gcc dot gnu dot org>

On Wed, 23 Nov 2011, Leith Bade wrote:

I have been hand optimising a loop that GCC 4.6 was not able to vectorise.
I have been keeping an eye on the assembly output of this loop and
have noticed GCC inserting unnecessary MOVAPS instructions.

Yes, there are several bugzilla entries showing that the register allocator is doing a fairly poor job on SSE/AVX registers...

--
Marc Glisse

References:
- GCC 4.6 is inserting unnecessary MOVAPS instructions for SSE intrinsics
  - From: Leith Bade

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