i965/gen6/blorp: Emit more flushes to workaround hangs

This is a squash of three related cherry-picks from master.

[PATCH 1/3]

  i965/gen6/blorp: Set need_workaround_flush immediately after primitive

  This patch makes the workaround code in gen6 blorp follow the pattern
  established in the regular draw path. It shouldn't result in any
  behavioral change.

  On gen6, there are two places where we emit 3D_CMD_PRIM: brw_emit_prim()
  and gen6_blorp_emit_primitive().  brw_emit_prim() sets
  need_workaround_flush immediately after emitting the primitive, but
  blorp does not. Blorp sets need_workaround_flush at the bottom of
  brw_blorp_exec().

  This patch moves the need_workaround_flush from brw_blorp_exec() to
  gen6_blorp_emit_primitive().  There is no need to set
  need_workaround_flush in gen7_blorp_emit_primitive() because the
  workaround applies only to gen6.

  Reviewed-by: Paul Berry <stereotype441@gmail.com>
  Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
  (cherry picked from commit 5e0cd58de4261e9dca7a15037192e7e9426a0207)

[PATCH 2/3]

  i965/gen6/blorp: Set need_workaround_flush at top of blorp

  Unconditionally set brw->need_workaround_flush at the top of gen6 blorp
  state emission.

  The art of emitting workaround flushes on Sandybridge is mysterious and
  not fully understood. Ken and I believe that
  intel_emit_post_sync_nonzero_flush() may be required when switching from
  regular drawing to blorp.  This is an extra safety measure to prevent
  undiscovered difficult-to-diagnose gpu hangs.

  I verified that on ChromeOS, pre-patch, need_workaround_flush was not
  set at the top of blorp, as Paul expected. To verify, I inserted the
  following debug code at the top of gen6_blorp_exec(), restarted the ui,
  and inspected the logs in /var/log/ui. The abort gets triggered so early
  that the browser never appears on the display.

      static void
      gen6_blorp_exec(...)
      {
          if (!brw->need_workaround_flush) {
              fprintf(stderr, "chadv: %s:%d\n", __FILE__, __LINE__);
              abort();
          }
          ...
      }

  CC: Kenneth Graunke <kenneth@whitecape.org>
  CC: Stéphane Marchesin <marcheu@chromium.org>
  Reviewed-by: Paul Berry <stereotype441@gmail.com>
  Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
  (cherry picked from commit 6a5c86f48675d2ca0975d69e0899e72afaab29e5)

[PATCH 3/3]

  i965/gen6/blorp: Remove redundant HiZ workaround

  Commit 1a92881 added extra flushes to fix a HiZ hang in
  WebGL Google Maps. With the extra flushes emitted by the previous two
  patches, the flushes added by 1a92881 are redundant.

  Tested with the same criteria as in 1a92881: by zooming in and out
  continuously for 2 hours on Sandybridge Chrome OS (codename
  Stumpy) without a hang.

  CC: Kenneth Graunke <kenneth@whitecape.org>
  CC: Stéphane Marchesin <marcheu@chromium.org>
  Reviewed-by: Paul Berry <stereotype441@gmail.com>
  Signed-off-by: Chad Versace <chad.versace@linux.intel.com>
  (cherry picked from commit 90368875e733171350c64c8dda52f81bd0705dd0)

  Conflicts:
  	src/mesa/drivers/dri/i965/gen6_blorp.cpp
mesa: Use IROUND instead of roundf.

roundf is not available on MSVC.

(cherry picked from commit bba8f10598866776ae198b363b3752c2e3bbb126)
cherry-ignore: Ignore 4 patches at teh request of the author, (Anuj).

For 3 of the 4, I was already ignoring them since they were not picking
cleanly. Now, Anuj has explicitly requested they be ignored since they all
depend on a series that is not yet on the 10.0 branch.
i965: Use sample barycentric coordinates with per sample shading

Current implementation of arb_sample_shading doesn't set 'Barycentric
Interpolation Mode' correctly. We use pixel barycentric coordinates
for per sample shading. Instead we should select perspective sample
or non-perspective sample barycentric coordinates.

It also enables using sample barycentric coordinates in case of a
fragment shader variable declared with 'sample' qualifier.
e.g. sample in vec4 pos;

A piglit test to verify the implementation has been posted on piglit
mailing list for review.

V2: Do not interpolate all the 'in' variables at sample position
    if fragment shader uses 'sample' qualifier with one of them.
    For example we have a fragment shader:
    #version 330
    #extension ARB_gpu_shader5: require
    sample in vec4 a;
    in vec4 b;
    main()
    {
      ...
    }

    Only 'a' should be sampled at sample location, not 'b'.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>
(cherry picked from commit a92e5f7cf63d496ad7830b5cea4bbab287c25b8e)
i965: Ignore 'centroid' interpolation qualifier in case of persample shading

This patch handles the use of 'centroid' qualifier with 'in' variables
in a fragment shader when persample shading is enabled. Per sample
shading for the whole fragment shader can be enabled by:
glEnable(GL_SAMPLE_SHADING) or using {gl_SamplePosition, gl_SampleID}
builtin variables in fragment shader. Explaining it below in more
detail.

/* Enable sample shading using OpenGL API */
glEnable(GL_SAMPLE_SHADING);
glMinSampleShading(1.0);

Example fragment shader:
in vec4 a;
centroid in vec4 b;
main()
{
  ...
}

Variable 'a' will be interpolated at sample location. But, what
interpolation should we use for variable 'b' ?

ARB_sample_shading recommends interpolation at sample position for
all the variables. GLSL 400 (and earlier) spec says that:

"When an interpolation qualifier is used, it overrides settings
established through the OpenGL API."
But, this text got deleted in later versions of GLSL.

NVIDIA's and AMD's proprietary linux drivers (at OpenGL 4.3)
interpolates at sample position. This convinces me to use
the similar approach on intel hardware.

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Chris Forbes <chrisf@ijw.co.nz>
(cherry picked from commit f5cfb4ae21df8eebfc6b86c0ce858b1c0a9160dd)

and

i965: Ignore 'centroid' interpolation qualifier in case of persample shading

I missed this change in commit f5cfb4a. It fixes the incorrect
rendering caused in Dolphin Emulator.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=73915

Signed-off-by: Anuj Phogat <anuj.phogat@gmail.com>
Tested-by: Markus Wick <wickmarkus@web.de>
Reviewed-by: Matt Turner <mattst88@gmail.com>
(cherry picked from commit dc2f94bc786768329973403248820a2e5249f102)