Re: [Qemu-devel] [PATCH v4 2/2] trace: Avoid implicit bool->integer conversions

["Daniel P. Berrange" <berrange@redhat.com>]

On Fri, Aug 12, 2016 at 05:33:46PM +0200, Lluís Vilanova wrote:
> An explicit if/else is clearer than arithmetic assuming #true is 1,
> while the compiler should be able to generate just as optimal code.
> 
> Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
> ---
>  stubs/trace-control.c  |   17 +++++++++++++++--
>  trace/control-target.c |   31 ++++++++++++++++++++++++++-----
>  2 files changed, 41 insertions(+), 7 deletions(-)

Reviewed-by: Daniel P. Berrange <berrange@redhat.com>

> 
> diff --git a/stubs/trace-control.c b/stubs/trace-control.c
> index 3740c38..2dfcd9f 100644
> --- a/stubs/trace-control.c
> +++ b/stubs/trace-control.c
> @@ -19,10 +19,23 @@ void trace_event_set_state_dynamic_init(TraceEvent *ev, bool state)
>  void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
>  {
>      TraceEventID id;
> +    bool state_pre;
>      assert(trace_event_get_state_static(ev));
>      id = trace_event_get_id(ev);
> -    trace_events_enabled_count += state - trace_events_dstate[id];
> -    trace_events_dstate[id] = state;
> +    /*
> +     * We ignore the "vcpu" property here, since there's no target code. Then
> +     * dstate can only be 1 or 0.
> +     */
> +    state_pre = trace_events_dstate[id];
> +    if (state_pre != state) {
> +        if (state) {
> +            trace_events_enabled_count++;
> +            trace_events_dstate[id] = 1;
> +        } else {
> +            trace_events_enabled_count--;
> +            trace_events_dstate[id] = 0;
> +        }
> +    }
>  }
>  
>  void trace_event_set_vcpu_state_dynamic(CPUState *vcpu,
> diff --git a/trace/control-target.c b/trace/control-target.c
> index 4ee3733..72081e2 100644
> --- a/trace/control-target.c
> +++ b/trace/control-target.c
> @@ -16,10 +16,22 @@
>  void trace_event_set_state_dynamic_init(TraceEvent *ev, bool state)
>  {
>      TraceEventID id = trace_event_get_id(ev);
> +    bool state_pre;
>      assert(trace_event_get_state_static(ev));
> -    /* Ignore "vcpu" property, since no vCPUs have been created yet */
> -    trace_events_enabled_count += state - trace_events_dstate[id];
> -    trace_events_dstate[id] = state;
> +    /*
> +     * We ignore the "vcpu" property here, since no vCPUs have been created
> +     * yet. Then dstate can only be 1 or 0.
> +     */
> +    state_pre = trace_events_dstate[id];
> +    if (state_pre != state) {
> +        if (state) {
> +            trace_events_enabled_count++;
> +            trace_events_dstate[id] = 1;
> +        } else {
> +            trace_events_enabled_count--;
> +            trace_events_dstate[id] = 0;
> +        }
> +    }
>  }
>  
>  void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
> @@ -31,9 +43,18 @@ void trace_event_set_state_dynamic(TraceEvent *ev, bool state)
>              trace_event_set_vcpu_state_dynamic(vcpu, ev, state);
>          }
>      } else {
> +        /* Without the "vcpu" property, dstate can only be 1 or 0 */
>          TraceEventID id = trace_event_get_id(ev);
> -        trace_events_enabled_count += state - trace_events_dstate[id];
> -        trace_events_dstate[id] = state;
> +        bool state_pre = trace_events_dstate[id];
> +        if (state_pre != state) {
> +            if (state) {
> +                trace_events_enabled_count++;
> +                trace_events_dstate[id] = 1;
> +            } else {
> +                trace_events_enabled_count--;
> +                trace_events_dstate[id] = 0;
> +            }
> +        }
>      }
>  }
>  
> 

Regards,
Daniel
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