[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v3 08/20] tcg-arm: Implement deposit for armv7
From: |
Richard Henderson |
Subject: |
Re: [Qemu-devel] [PATCH v3 08/20] tcg-arm: Implement deposit for armv7 |
Date: |
Thu, 28 Mar 2013 09:22:06 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 |
On 03/28/2013 09:15 AM, Peter Maydell wrote:
>> + /* ??? Without bfi, we could improve over generic code by combining
>> + the right-shift from a non-zero ofs with the orr. We do run into
>> + problems when rd == rs, and the mask generated from ofs+len don't
>> + fit into an immediate. We would have to be careful not to pessimize
>> + wrt the optimizations performed on the expanded code. */
>> + return use_armv7_instructions;
>
> Strictly speaking BFI is v6T2, but there doesn't seem much point
> in making the distinction given it would only affect the rare
> ARM1156. (Personally I don't think there's much point worrying about
> optmising codegen for anything pre-v7 at all.)
Fair enough. I could update the comment to include v6t2, since I've done
similar for e.g. v6k (while retaining the v7 test) elsewhere in the patch set.
> What guarantees us that we won't see a length of 0?
> The tcg/README description doesn't say that's invalid
> and I don't think the optimize pass handles it (maybe I
> missed it).
We can patch the readme, and the asserts in tcg-op.h if you like.
I've assumed elsewhere that we won't see a zero length. E.g. none of the other
cpus -- ppc, hppa, ia64 -- can encode that either.
r~
- Re: [Qemu-devel] [PATCH v3 05/20] tcg-arm: Handle constant arguments to add2/sub2, (continued)
[Qemu-devel] [PATCH v3 03/20] tcg-arm: Allow constant first argument to sub, Richard Henderson, 2013/03/28
[Qemu-devel] [PATCH v3 06/20] tcg-arm: Improve constant generation, Richard Henderson, 2013/03/28
[Qemu-devel] [PATCH v3 07/20] tcg-arm: Fold epilogue into INDEX_op_exit_tb, Richard Henderson, 2013/03/28
[Qemu-devel] [PATCH v3 08/20] tcg-arm: Implement deposit for armv7, Richard Henderson, 2013/03/28
[Qemu-devel] [PATCH v3 09/20] tcg-arm: Implement division instructions, Richard Henderson, 2013/03/28
[Qemu-devel] [PATCH v3 10/20] tcg-arm: Use TCG_REG_TMP name for the tcg temporary, Richard Henderson, 2013/03/28
[Qemu-devel] [PATCH v3 11/20] tcg-arm: Use R12 for the tcg temporary, Richard Henderson, 2013/03/28
[Qemu-devel] [PATCH v3 12/20] tcg-arm: Cleanup multiply subroutines, Richard Henderson, 2013/03/28
[Qemu-devel] [PATCH v3 13/20] tcg-arm: Cleanup tcg_out_goto_label, Richard Henderson, 2013/03/28
[Qemu-devel] [PATCH v3 14/20] tcg-arm: Cleanup goto_tb handling, Richard Henderson, 2013/03/28