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Re: [RFC] Various questions about TCG implementation, DRM patches dealin
From: |
Richard Henderson |
Subject: |
Re: [RFC] Various questions about TCG implementation, DRM patches dealing with pointers over guest-host barrier. |
Date: |
Tue, 19 May 2020 07:51:55 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 |
On 5/17/20 4:05 PM, Catherine A. Frederick wrote:
> - I've been implementing an instruction scheduler(list scheduler, with
> priority
> given to most successors) for TCG and currently if I replace instructions in
> s->ops(the TCG context) I get a crash later in tcg_reg_alloc_op, even if the
> instruction stream is identical. Is there anything else I need to move when I
> do this?
If you're getting a crash in tcg_reg_alloc_op, are you updating liveness info?
Where are you inserting your scheduler in the list of passes?
> - Is insn_start necessary to have in order(and what does it do?)? These
> currently are serializing instructions in my scheduler and significantly limit
> my reordering as they create lots of dependencies every few instructions.
insn_start is required for unwinding from exceptions. You can consider it a
barrier for call and qemu_ld/st. Anything else cannot raise an exception and
can be moved.
r~