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Re: [PING*2][PATCH] Extend mode-switching to support toggle (1/2)
- From: Oleg Endo <oleg dot endo at t-online dot de>
- To: Joern Rennecke <joern dot rennecke at embecosm dot com>
- Cc: Christian Bruel <christian dot bruel at st dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Jeff Law <law at redhat dot com>, Kaz Kojima <kkojima at rr dot iij4u dot or dot jp>
- Date: Tue, 13 May 2014 23:41:03 +0200
- Subject: Re: [PING*2][PATCH] Extend mode-switching to support toggle (1/2)
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- References: <535E0C86 dot 400 at st dot com> <537089D8 dot 8040106 at st dot com> <53708F1D dot 1080308 at st dot com> <CAMqJFCpxG2RyOZ0NsYiBV5PUU4A+8kWaq22am+GR=e22i-uf0g at mail dot gmail dot com> <5370BB9D dot 1090803 at st dot com> <CAMqJFCovAjbuJK6puakdUZu-mDdUdWS92exwLdz3fKGO+goMZA at mail dot gmail dot com> <1399934352 dot 2344 dot 26 dot camel at yam-132-YW-E178-FTW> <CAMqJFCrBAmXuBe6JVifM-wEvN05Ny8AEsbBT0TfmHistSWfr-Q at mail dot gmail dot com>
On Tue, 2014-05-13 at 09:10 +0100, Joern Rennecke wrote:
> On 12 May 2014 23:39, Oleg Endo <oleg.endo@t-online.de> wrote:
>
> > This is the same as changing/setting the FP modes (PR, SZ) on SH while
> > preserving the other FPSCR bits, or did I miss something?
>
> It's more like if you have to control multiple bits at once to get a
> specific mode.
> Say you have to turn SZ off and PR on. You you knew that only one bit needs
> changing, you can do with one less arithmetic operation.
Right. I was thinking to add FPSCR.SZ mode switching to SH, in order to
do float vector moves. For that SZ and PR need to be switched both at
the same time (only SH4A has both, fpchg and fschg). So basically I'd
add another mode entity, which would emit SZ mode changes in addition to
the PR mode changes. But then adjacent FPSCR-changing insns could be
combined ... any idea/suggestion how to accomplish that?
Cheers,
Oleg