Re: [PATCH 1/6] drm/i915: Compile time concatenate WARN_ON macro strings

[Chris Wilson <chris@chris-wilson.co.uk>]

On Thu, Dec 17, 2015 at 09:25:46PM +0200, Joonas Lahtinen wrote:
> Using __stringify(x) instead of #x adds support for macros as
> a parameter and reduces runtime overhead.
> 
> Slightly increases the .text size but should not matter.
> 
> Cc: Rob Clark <robdclark@gmail.com>
> Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/i915_drv.h | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 1d28d90..fe3e76d 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -69,11 +69,11 @@
>  		BUILD_BUG_ON(__i915_warn_cond); \
>  	WARN(__i915_warn_cond, "WARN_ON(" #x ")"); })
>  #else
> -#define WARN_ON(x) WARN((x), "WARN_ON(%s)", #x )
> +#define WARN_ON(x) WARN((x), "WARN_ON(" __stringify(x) ")")
>  #endif
>  
>  #undef WARN_ON_ONCE
> -#define WARN_ON_ONCE(x) WARN_ONCE((x), "WARN_ON_ONCE(%s)", #x )
> +#define WARN_ON_ONCE(x) WARN_ONCE((x), "WARN_ON_ONCE(" __stringify(x) ")")
>  
>  #define MISSING_CASE(x) WARN(1, "Missing switch case (%lu) in %s\n", \
>  			     (long) (x), __func__);
> @@ -97,12 +97,14 @@
>  })
>  
>  #define I915_STATE_WARN_ON(condition) ({				\
> +	static const char __warn_on_txt[] =				\
> +		"WARN_ON(" __stringify(condition) ")\n";		\
>  	int __ret_warn_on = !!(condition);				\
>  	if (unlikely(__ret_warn_on)) {					\
>  		if (i915.verbose_state_checks)				\
> -			WARN(1, "WARN_ON(" #condition ")\n");		\
> +			WARN(1, __warn_on_txt);				\
>  		else 							\
> -			DRM_ERROR("WARN_ON(" #condition ")\n");		\
> +			DRM_ERROR(__warn_on_txt);			\
>  	}								\

Bikeshedding, sorry.

#define I915_STATE_WARN_ON(condition) ({				\
  	int __ret_warn_on = !!(condition);				\
  	if (unlikely(__ret_warn_on)) {					\
		static const char __warn_on_txt[] =			\
			"WARN_ON(" __stringify(condition) ")\n";	\
  		if (!WARN(i915.verbose_state_checks, __warn_on_txt);	\
			DRM_ERROR(__warn_on_txt);			\
  	}								\
  	unlikely(__ret_warn_on);					\
  })
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre
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