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Re: GCC Compiler Optimization ignores or mistreats MFENCE memory barrier related instruction
- From: Jakub Jelinek <jakub at redhat dot com>
- To: Umesh Kalappa <umesh dot kalappa0 at gmail dot com>
- Cc: Alexander Monakov <amonakov at ispras dot ru>, "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>
- Date: Mon, 7 May 2018 10:38:30 +0200
- Subject: Re: GCC Compiler Optimization ignores or mistreats MFENCE memory barrier related instruction
- References: <CAGfacvSeTBiT=zofrzZ-TvVia8t+fBo=dhNpKMnCdmAngo4nLA@mail.gmail.com>
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
On Mon, May 07, 2018 at 01:58:48PM +0530, Umesh Kalappa wrote:
> CCed Jakub,
> > Agree that float division don't touch memory ,but fdiv result (stack
> > register ) is stored back to a memory i.e fResult .
That doesn't really matter. It is stored to a stack spill slot, something
that doesn't have address taken and other code (e.g. in other threads) can't
in a valid program access it. That is not considered memory for the
inline-asm, only objects that must live in memory count.
Jakub