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Re: [Qemu-ppc] [Qemu-devel] [PATCH 28/32] ppc: Avoid double translation
From: |
Benjamin Herrenschmidt |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] [PATCH 28/32] ppc: Avoid double translation for lvx/lvxl/stvx/stvxl |
Date: |
Fri, 29 Jul 2016 12:13:01 +1000 |
On Fri, 2016-07-29 at 06:19 +0530, Richard Henderson wrote:
> This, I'm not so keen on.
>
> (1) The helper, since it writes to registers controlled by tcg, must be
> described to clobber all registers. Which will noticeably increase memory
> traffic to ENV. For instance, you won't be able to hold the guest register
> holding the address in a host register across the call.
Ah I wasn't aware of this. How do you describe such a clobber ? Can I describe
specifically which one is clobbered ? I didn't think TCG kept track of the
vector
halves but I must admit I'm still a bit new with TCG in general.
I noticed other constructs doing that (passing a register number to an opcode),
what do I do to ensure the right clobbers are there ?
> > (2) We're going to have to teach tcg about 16-byte data types soon anyway,
> > for
> the proper emulation of 16-byte atomic operations.
Is anybody working on this already ? I thought about that approach as
it would definitely make things easier for that and a couple of other
cases such as lq/stq.
Cheers,
Ben.
- [Qemu-ppc] [PATCH 21/32] ppc: Don't update NIP on conditional trap instructions, (continued)
- [Qemu-ppc] [PATCH 21/32] ppc: Don't update NIP on conditional trap instructions, Benjamin Herrenschmidt, 2016/07/26
- [Qemu-ppc] [PATCH 24/32] ppc: Make alignment exceptions suck less, Benjamin Herrenschmidt, 2016/07/26
- [Qemu-ppc] [PATCH 27/32] ppc: Fix CFAR updates, Benjamin Herrenschmidt, 2016/07/26
- [Qemu-ppc] [PATCH 31/32] ppc: load/store multiple and string insns don't do LE, Benjamin Herrenschmidt, 2016/07/26
- [Qemu-ppc] [PATCH 28/32] ppc: Avoid double translation for lvx/lvxl/stvx/stvxl, Benjamin Herrenschmidt, 2016/07/26
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 28/32] ppc: Avoid double translation for lvx/lvxl/stvx/stvxl, Benjamin Herrenschmidt, 2016/07/29
- Re: [Qemu-ppc] [Qemu-devel] [PATCH 28/32] ppc: Avoid double translation for lvx/lvxl/stvx/stvxl, Richard Henderson, 2016/07/29
[Qemu-ppc] [PATCH 29/32] ppc: Don't set access_type on all load/stores on hash64, Benjamin Herrenschmidt, 2016/07/26
[Qemu-ppc] [PATCH 30/32] ppc: Use a helper to generate "LE unsupported" alignment interrupts, Benjamin Herrenschmidt, 2016/07/26
[Qemu-ppc] [PATCH 22/32] ppc: Don't update NIP if not taking alignment exceptions, Benjamin Herrenschmidt, 2016/07/26
[Qemu-ppc] [PATCH 26/32] ppc: Speed up dcbz, Benjamin Herrenschmidt, 2016/07/26