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Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated"
From: |
Peter Maydell |
Subject: |
Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated" |
Date: |
Fri, 10 Sep 2021 17:00:12 +0100 |
On Tue, 7 Sept 2021 at 15:11, Richard Henderson
<richard.henderson@linaro.org> wrote:
> > * gen_update_fp_context() -- this function gets called for pretty
> > much every FP/MVE insn (as part of vfp_access_check), and it
> > can in rare cases update the FPSCR.LTPSIZE and the VPR. I guess
> > this means we really do need to end the TB
> > if (MVE && s->v7m_new_fp_ctxt_needed) (ie the comment in
> > gen_update_fp_context "We don't need to arrange to end the TB,
> > because [we don't cache FPSCR in TB flags]" is no longer true).
> > That seems likely to be painful because some of the insns that
> > do a vfp_access_check do complicated things with the TB exits
> > (eg WLSTP, LETP) that are going to override a naive setting of
> > is_jmp in gen_update_fp_context()...
>
> Well, we could let gen_goto_tb see that is_jmp is already UPDATE_NOCHAIN, and
> suppress the
> goto_tb in that case. That would seem to take care of any entry into
> gen_jmp(_tb).
We actually already have code that sets is_jmp (to DISAS_UPDATE_EXIT)
from gen_preserve_fp_state() -- we do that if we're using icount,
setting DISAS_UPDATE_EXIT to force this to be the last insn in the TB.
Do icount IO instructions need to avoid a possible goto_tb ?
I suppose we do want them to go back to the main loop.
This suggests that we need to make gen_goto_tb() look at
the is_jmp value anyway, regardless of this series.
-- PMM
- [PATCH 0/4] target/arm: Use TCG vector ops for MVE, Peter Maydell, 2021/09/02
- [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Peter Maydell, 2021/09/02
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Richard Henderson, 2021/09/03
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Peter Maydell, 2021/09/03
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Richard Henderson, 2021/09/03
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Peter Maydell, 2021/09/03
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Richard Henderson, 2021/09/07
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Richard Henderson, 2021/09/07
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated",
Peter Maydell <=
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Richard Henderson, 2021/09/12
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Peter Maydell, 2021/09/09
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Richard Henderson, 2021/09/10
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Peter Maydell, 2021/09/10
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Richard Henderson, 2021/09/10
- Re: [PATCH 1/4] target/arm: Add TB flag for "MVE insns not predicated", Peter Maydell, 2021/09/09
[PATCH 3/4] target/arm: Optimize MVE arithmetic ops, Peter Maydell, 2021/09/02
[PATCH 4/4] target/arm: Optimize MVE VNEG, VABS, Peter Maydell, 2021/09/02