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

[Richard Henderson <richard.henderson@linaro.org>]

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~