Peter Maydell <peter.mayd...@linaro.org> writes:
> On Mon, 18 May 2020 at 00:23, Catherine A. Frederick > <agrecascino...@gmail.com> wrote: >> Hi, I've been patching TCG for my own purposes recently and I was >> wondering a few things. That being: >> <snip> >> - 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? > > This one's out of my field of knowledge; Richard might know. I'm a little unclear in what is happening here. For TCG plugins we insert dummy ops into the stream so they can be replaced or removed at a later phase in the translation. >> - 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. > > The primary purpose of insn_start is to save information about the > current instruction in a metadata <snip> > Finally, I haven't checked, but I suspect the new TCG plugin APIs > implicitly assume that code for each insn is generated serially, > ie that a plugin can do "for each instruction" type work on a > callback that hangs off the insn_start op. Spoiler alert: Yes it does ;-) -- Alex Bennée
