[Mesa-dev] [PATCH] i965: Support GL_CLAMP natively on Broadwell.

[Kenneth Graunke]

The new hardware actually supports this OpenGL 1.x feature natively,
so we can finally drop our shader workarounds.

Not many applications use GL_CLAMP, and most use it unintentionally, but
it's trivial to do right, so we should.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/brw_defines.h          |  1 +
 src/mesa/drivers/dri/i965/brw_wm.c               |  3 ++-
 src/mesa/drivers/dri/i965/brw_wm_sampler_state.c | 13 ++++++++++---
 3 files changed, 13 insertions(+), 4 deletions(-)

No Piglit regressions on Broadwell.

diff --git a/src/mesa/drivers/dri/i965/brw_defines.h b/src/mesa/drivers/dri/i965/brw_defines.h
index c38e447..8996b02 100644
--- a/src/mesa/drivers/dri/i965/brw_defines.h
+++ b/src/mesa/drivers/dri/i965/brw_defines.h
@@ -606,6 +606,7 @@
 #define BRW_TEXCOORDMODE_CUBE            3
 #define BRW_TEXCOORDMODE_CLAMP_BORDER    4
 #define BRW_TEXCOORDMODE_MIRROR_ONCE     5
+#define GEN8_TEXCOORDMODE_HALF_BORDER    6
 
 #define BRW_THREAD_PRIORITY_NORMAL   0
 #define BRW_THREAD_PRIORITY_HIGH     1
diff --git a/src/mesa/drivers/dri/i965/brw_wm.c b/src/mesa/drivers/dri/i965/brw_wm.c
index c2d38b3..d716e6f 100644
--- a/src/mesa/drivers/dri/i965/brw_wm.c
+++ b/src/mesa/drivers/dri/i965/brw_wm.c
@@ -347,7 +347,8 @@ brw_populate_sampler_prog_key_data(struct gl_context *ctx,
          if (alpha_depth || (brw->gen < 8 && !brw->is_haswell))
             key->swizzles[s] = brw_get_texture_swizzle(ctx, t);
 
-	 if (sampler->MinFilter != GL_NEAREST &&
+	 if (brw->gen < 8 &&
+             sampler->MinFilter != GL_NEAREST &&
 	     sampler->MagFilter != GL_NEAREST) {
 	    if (sampler->WrapS == GL_CLAMP)
 	       key->gl_clamp_mask[0] |= 1 << s;
diff --git a/src/mesa/drivers/dri/i965/brw_wm_sampler_state.c b/src/mesa/drivers/dri/i965/brw_wm_sampler_state.c
index 6f8dde4..8a4bfea 100644
--- a/src/mesa/drivers/dri/i965/brw_wm_sampler_state.c
+++ b/src/mesa/drivers/dri/i965/brw_wm_sampler_state.c
@@ -55,9 +55,16 @@ translate_wrap_mode(struct brw_context *brw, GLenum wrap, bool using_nearest)
       /* GL_CLAMP is the weird mode where coordinates are clamped to
        * [0.0, 1.0], so linear filtering of coordinates outside of
        * [0.0, 1.0] give you half edge texel value and half border
-       * color.  The fragment shader will clamp the coordinates, and
-       * we set clamp_border here, which gets the result desired.  We
-       * just use clamp(_to_edge) for nearest, because for nearest
+       * color.
+       *
+       * Gen8+ supports this natively.
+       */
+      if (brw->gen >= 8)
+         return GEN8_TEXCOORDMODE_HALF_BORDER;
+
+      /* On Gen4-7.5, we clamp the coordinates in the fragment shader
+       * and set clamp_border here, which gets the result desired.
+       * We just use clamp(_to_edge) for nearest, because for nearest
        * clamping to 1.0 gives border color instead of the desired
        * edge texels.
        */
-- 
1.9.1