Re: [PATCH 07/22] plugins: Use emit_before_op for PLUGIN_GEN_AFTER_INSN

[Pierrick Bouvier]

On 3/19/24 23:56, Richard Henderson wrote:
> On 3/19/24 03:32, Pierrick Bouvier wrote:
> > >    static void plugin_gen_inject(struct qemu_plugin_tb *plugin_tb)
> > >    {
> > > -    TCGOp *op;
> > > +    TCGOp *op, *next;
> > >        int insn_idx = -1;
> > >        pr_ops();
> > > -    QTAILQ_FOREACH(op, &tcg_ctx->ops, link) {
> > > +    /*
> > > +     * While injecting code, we cannot afford to reuse any ebb temps
> > > +     * that might be live within the existing opcode stream.
> > > +     * The simplest solution is to release them all and create new.
> > > +     */
> > > +    memset(tcg_ctx->free_temps, 0, sizeof(tcg_ctx->free_temps));
> > > +
> >
> > Not an expert at this, but wouldn't that break an existing TB that already has 
> > some ops on
> > those temps?
>
> No, this only affects allocation of new temps -- if free_temps is empty, a new 
> temp will
> be allocated from tcg_ctx->nb_temps++.
>
> Zeroing free_temps here ensures that we *do not* reuse a temp that might 
> already be live
> across any plugin insertion point.  Between insertion points, we will free 
> plugin temps
> and only reuse those.

Thanks, by looking at tcg_temp_new_internal fn, and with your 
explaination, it makes more sense.

> r~