[Mesa-dev] [PATCH 6/6] intel: Detile stencil buffer only if necessary

[Chad Versace]

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On 11/15/2011 06:16 PM, Eric Anholt wrote:
> On Sun, 13 Nov 2011 22:32:15 -0800, Chad Versace <chad.versace at linux.intel.com> wrote:
>> In intel_map_renderbuffer_s8(), detile and copy the stencil buffer into
>> the temporary buffer only if the renderbuffer is mapped in read mode. If
>> the caller never going to read the bits but just clobber them, then it's
>> wasted effort to detile the stencil buffer.
>>
>> CC: Eric Anholt <eric at anholt.net>
>> Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
> 
> I don't think this is correct.
> 
> Imagine something that isn't writing all of the pixels, but definitely
> isn't reading data before writing.  It might sensibly ask for
> GL_WRITE_BIT but not GL_READ_BIT, and then all the pixels it doesn't
> write get trashed when the whole rectangle is written back out.
> 
> If the mode contained GL_MAP_INVALIDATE_RANGE_BIT (basically,
> interpreting the mode argument like GL_ARB_map_buffer_range, which was
> my intent if not Brian's), this would be reasonable.

You're correct. This patch is nakd.

- ----
Chad Versace
chad.versace at linux.intel.com
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