cpu-exec: Allow "-d exec" in non-debug builds (drop CONFIG_DEBUG_EXEC)

The CONFIG_DEBUG_EXEC define compiles out a single qemu_log_mask()
call, which is a pretty trivial cost even for something in the main
cpu_exec() loop.  Having this be conditionally defined means that
'-d exec' on a non-debug build will silently do nothing.  Drop the
define and the configure machinery that sets it, in favour of just
always allowing this log option to be enabled at runtime.  As a
concession to the mainloopiness, we use qemu_loglevel_mask()+qemu_log()
rather than qemu_log_mask() to avoid the function call overhead.

Note that DEBUG_DISAS is always defined, so removing the
'|| defined(CONFIG_DEBUG_EXEC)' from those conditionals makes
no behavioural change for that logging.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
I've been burnt at least once by asking a user to do a '-d exec'
log only to find it didn't actually log anything...

 configure  |  3 ---
 cpu-exec.c | 15 ++++++---------
 2 files changed, 6 insertions(+), 12 deletions(-)

On Thu, Apr 11, 2013 at 09:21:46PM +0100, Peter Maydell wrote:
> The CONFIG_DEBUG_EXEC define compiles out a single qemu_log_mask()
> call, which is a pretty trivial cost even for something in the main
> cpu_exec() loop.  Having this be conditionally defined means that
> '-d exec' on a non-debug build will silently do nothing.  Drop the
> define and the configure machinery that sets it, in favour of just
> always allowing this log option to be enabled at runtime.  As a
> concession to the mainloopiness, we use qemu_loglevel_mask()+qemu_log()
> rather than qemu_log_mask() to avoid the function call overhead.
> 
> Note that DEBUG_DISAS is always defined, so removing the
> '|| defined(CONFIG_DEBUG_EXEC)' from those conditionals makes
> no behavioural change for that logging.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

I agree, lack of -d exec has bitten me a couple of times
aswell. A separate patch with an option to disable tb-
chaining would also be helpful imo.

Acked-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>



> ---
> I've been burnt at least once by asking a user to do a '-d exec'
> log only to find it didn't actually log anything...
> 
>  configure  |  3 ---
>  cpu-exec.c | 15 ++++++---------
>  2 files changed, 6 insertions(+), 12 deletions(-)
> 
> diff --git a/configure b/configure
> index 1ed939a..73df181 100755
> --- a/configure
> +++ b/configure
> @@ -3471,9 +3471,6 @@ echo "ARCH=$ARCH" >> $config_host_mak
>  if test "$debug_tcg" = "yes" ; then
>    echo "CONFIG_DEBUG_TCG=y" >> $config_host_mak
>  fi
> -if test "$debug" = "yes" ; then
> -  echo "CONFIG_DEBUG_EXEC=y" >> $config_host_mak
> -fi
>  if test "$strip_opt" = "yes" ; then
>    echo "STRIP=${strip}" >> $config_host_mak
>  fi
> diff --git a/cpu-exec.c b/cpu-exec.c
> index e74e556..235ddee 100644
> --- a/cpu-exec.c
> +++ b/cpu-exec.c
> @@ -23,8 +23,6 @@
>  #include "qemu/atomic.h"
>  #include "sysemu/qtest.h"
>  
> -//#define CONFIG_DEBUG_EXEC
> -
>  bool qemu_cpu_has_work(CPUState *cpu)
>  {
>      return cpu_has_work(cpu);
> @@ -567,7 +565,7 @@ int cpu_exec(CPUArchState *env)
>                      env->exception_index = EXCP_INTERRUPT;
>                      cpu_loop_exit(env);
>                  }
> -#if defined(DEBUG_DISAS) || defined(CONFIG_DEBUG_EXEC)
> +#if defined(DEBUG_DISAS)
>                  if (qemu_loglevel_mask(CPU_LOG_TB_CPU)) {
>                      /* restore flags in standard format */
>  #if defined(TARGET_I386)
> @@ -582,7 +580,7 @@ int cpu_exec(CPUArchState *env)
>                      log_cpu_state(env, 0);
>  #endif
>                  }
> -#endif /* DEBUG_DISAS || CONFIG_DEBUG_EXEC */
> +#endif /* DEBUG_DISAS */
>                  spin_lock(&tcg_ctx.tb_ctx.tb_lock);
>                  tb = tb_find_fast(env);
>                  /* Note: we do it here to avoid a gcc bug on Mac OS X when
> @@ -594,11 +592,10 @@ int cpu_exec(CPUArchState *env)
>                      next_tb = 0;
>                      tcg_ctx.tb_ctx.tb_invalidated_flag = 0;
>                  }
> -#ifdef CONFIG_DEBUG_EXEC
> -                qemu_log_mask(CPU_LOG_EXEC, "Trace %p [" TARGET_FMT_lx "] %s\n",
> -                             tb->tc_ptr, tb->pc,
> -                             lookup_symbol(tb->pc));
> -#endif
> +                if (qemu_loglevel_mask(CPU_LOG_EXEC)) {
> +                    qemu_log("Trace %p [" TARGET_FMT_lx "] %s\n",
> +                             tb->tc_ptr, tb->pc, lookup_symbol(tb->pc));
> +                }
>                  /* see if we can patch the calling TB. When the TB
>                     spans two pages, we cannot safely do a direct
>                     jump. */
> -- 
> 1.7.11.4
> 
>

On Thu, Apr 11, 2013 at 09:21:46PM +0100, Peter Maydell wrote:
> The CONFIG_DEBUG_EXEC define compiles out a single qemu_log_mask()
> call, which is a pretty trivial cost even for something in the main
> cpu_exec() loop.  Having this be conditionally defined means that
> '-d exec' on a non-debug build will silently do nothing.  Drop the
> define and the configure machinery that sets it, in favour of just
> always allowing this log option to be enabled at runtime.  As a
> concession to the mainloopiness, we use qemu_loglevel_mask()+qemu_log()
> rather than qemu_log_mask() to avoid the function call overhead.
> 
> Note that DEBUG_DISAS is always defined, so removing the
> '|| defined(CONFIG_DEBUG_EXEC)' from those conditionals makes
> no behavioural change for that logging.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> I've been burnt at least once by asking a user to do a '-d exec'
> log only to find it didn't actually log anything...
> 
>  configure  |  3 ---
>  cpu-exec.c | 15 ++++++---------
>  2 files changed, 6 insertions(+), 12 deletions(-)

Thanks, applied to the trivial patches tree:
https://github.com/stefanha/qemu/commits/trivial-patches

Stefan