Re: [PATCH 2/3] drm/i915: Promote IS_BROADWELL to a simple macro

From: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
To: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
Cc: Intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 2/3] drm/i915: Promote IS_BROADWELL to a simple macro
Date: Fri, 6 May 2016 15:44:05 +0100	[thread overview]
Message-ID: <572CADB5.900@linux.intel.com> (raw)
In-Reply-To: <20160506142918.GD4329@intel.com>

On 06/05/16 15:29, Ville Syrjälä wrote:
> On Fri, May 06, 2016 at 03:18:16PM +0100, Tvrtko Ursulin wrote:
>>
>> On 06/05/16 15:00, Ville Syrjälä wrote:
>>> On Fri, May 06, 2016 at 02:43:50PM +0100, Tvrtko Ursulin wrote:
>>>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>>
>>>> If we allow it a dedicated flag in dev_priv we enable the
>>>> compiler to nicely optimize conditions like IS_HASSWELL ||
>>>> IS_BROADWELL.
>>>>
>>>> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>>> ---
>>>>    drivers/gpu/drm/i915/i915_drv.c | 4 ++++
>>>>    drivers/gpu/drm/i915/i915_drv.h | 3 ++-
>>>>    2 files changed, 6 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
>>>> index 9fd221c97275..da6532da44e3 100644
>>>> --- a/drivers/gpu/drm/i915/i915_drv.c
>>>> +++ b/drivers/gpu/drm/i915/i915_drv.c
>>>> @@ -300,22 +300,26 @@ static const struct intel_device_info intel_haswell_m_info = {
>>>>    static const struct intel_device_info intel_broadwell_d_info = {
>>>>    	BDW_FEATURES,
>>>>    	.gen = 8,
>>>> +	.is_broadwell = 1,
>>>>    };
>>>>
>>>>    static const struct intel_device_info intel_broadwell_m_info = {
>>>>    	BDW_FEATURES,
>>>>    	.gen = 8, .is_mobile = 1,
>>>> +	.is_broadwell = 1,
>>>>    };
>>>>
>>>>    static const struct intel_device_info intel_broadwell_gt3d_info = {
>>>>    	BDW_FEATURES,
>>>>    	.gen = 8,
>>>> +	.is_broadwell = 1,
>>>>    	.ring_mask = RENDER_RING | BSD_RING | BLT_RING | VEBOX_RING | BSD2_RING,
>>>>    };
>>>>
>>>>    static const struct intel_device_info intel_broadwell_gt3m_info = {
>>>>    	BDW_FEATURES,
>>>>    	.gen = 8, .is_mobile = 1,
>>>> +	.is_broadwell = 1,
>>>>    	.ring_mask = RENDER_RING | BSD_RING | BLT_RING | VEBOX_RING | BSD2_RING,
>>>>    };
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
>>>> index c6351016eaf0..459561991081 100644
>>>> --- a/drivers/gpu/drm/i915/i915_drv.h
>>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
>>>> @@ -735,6 +735,7 @@ struct intel_csr {
>>>>    	func(is_valleyview) sep \
>>>>    	func(is_cherryview) sep \
>>>>    	func(is_haswell) sep \
>>>> +	func(is_broadwell) sep \
>>>>    	func(is_skylake) sep \
>>>>    	func(is_broxton) sep \
>>>>    	func(is_kabylake) sep \
>>>
>>> We could just replace all of these with a single enum and save a bunch
>>> of space.
>>
>> Bitfield is really nice here because compiler can then merge tests like
>> IS_HASWELL || IS_BROADWELL into a single test instruction.
>
> Most if not all of those are in modeset code so I'm not entirely
> convinced micro-optimizing that is all that useful.

Maybe not, but IS_BROADWELL was just tasteless and it is better to save 
instructions across everything than a bit in dev_priv.

> Bunch of times I've just wished I could write 'whatever >= G4X' instead
> of 'IS_G4X || gen >= 5' simply for readability.

I don't even know what G4X is so can't really follow what you mean. Is 
it like Gen4.5, or Gen5-- ? So I can't figure out what kind of scheme 
you propose.

Regards,

Tvrtko
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx