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

[Richard Henderson]

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.


r~