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Re: [Qemu-devel] [PATCH 2/2] qemu-common.h: optimise muldiv64 for x86_64
From: |
Peter Maydell |
Subject: |
Re: [Qemu-devel] [PATCH 2/2] qemu-common.h: optimise muldiv64 for x86_64 architecture |
Date: |
Fri, 9 Jan 2015 16:10:00 +0000 |
On 9 January 2015 at 16:08, Frediano Ziglio <address@hidden> wrote:
> I agree (after some digging) we are not sure we won't get that
> overflow. Agree to drop the second patch. However I would retain the
> first. Compiler can use it to optimize much easier. For instance if
> compiler understand that the multiplication fits into a 64 bit can
> decide to avoid the 128 bit operation easily, not so easy with all
> these shift, multiply, division and union structure.
Yes, the uint128_t patch is a good idea.
-- PMM
Re: [Qemu-devel] [PATCH 1/2] qemu-common.h: optimise muldiv64 if int128 is available, Peter Maydell, 2015/01/09