llvmpipe: intrinsics version of triangle coeficient calculation

Looks nice, but makes almost no impact on performance - maybe
a percent or so in isosurf, nothing elsewhere.  May be of use
later on.

5 files changed, 577 insertions, 300 deletions

diff --git a/src/gallium/drivers/llvmpipe/SConscript b/src/gallium/drivers/llvmpipe/SConscript
index 5583fca38e..8d57db72cf 100644
--- a/src/gallium/drivers/llvmpipe/SConscript
+++ b/src/gallium/drivers/llvmpipe/SConscript
@@ -63,6 +63,8 @@ llvmpipe = env.ConvenienceLibrary(
 		'lp_setup_line.c',
 		'lp_setup_point.c',
 		'lp_setup_tri.c',
+		'lp_setup_coef.c',
+		'lp_setup_coef_intrin.c',
 		'lp_setup_vbuf.c',
 		'lp_state_blend.c',
 		'lp_state_clip.c',
diff --git a/src/gallium/drivers/llvmpipe/lp_setup_coef.c b/src/gallium/drivers/llvmpipe/lp_setup_coef.c
new file mode 100644
index 0000000000..95e3e8fffe
--- /dev/null
+++ b/src/gallium/drivers/llvmpipe/lp_setup_coef.c
@@ -0,0 +1,258 @@
+/**************************************************************************
+ *
+ * Copyright 2010, VMware.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+
+/*
+ * Binning code for triangles
+ */
+
+#include "util/u_math.h"
+#include "util/u_memory.h"
+#include "lp_perf.h"
+#include "lp_setup_context.h"
+#include "lp_setup_coef.h"
+#include "lp_rast.h"
+#include "lp_state_fs.h"
+
+#if !defined(PIPE_ARCH_SSE)
+
+/**
+ * Compute a0 for a constant-valued coefficient (GL_FLAT shading).
+ */
+static void constant_coef( struct lp_rast_shader_inputs *inputs,
+                           unsigned slot,
+			   const float value,
+                           unsigned i )
+{
+   inputs->a0[slot][i] = value;
+   inputs->dadx[slot][i] = 0.0f;
+   inputs->dady[slot][i] = 0.0f;
+}
+
+
+
+static void linear_coef( struct lp_rast_shader_inputs *inputs,
+                         const struct lp_tri_info *info,
+                         unsigned slot,
+                         unsigned vert_attr,
+                         unsigned i)
+{
+   float a0 = info->v0[vert_attr][i];
+   float a1 = info->v1[vert_attr][i];
+   float a2 = info->v2[vert_attr][i];
+
+   float da01 = a0 - a1;
+   float da20 = a2 - a0;
+   float dadx = (da01 * info->dy20_ooa - info->dy01_ooa * da20);
+   float dady = (da20 * info->dx01_ooa - info->dx20_ooa * da01);
+
+   inputs->dadx[slot][i] = dadx;
+   inputs->dady[slot][i] = dady;
+
+   /* calculate a0 as the value which would be sampled for the
+    * fragment at (0,0), taking into account that we want to sample at
+    * pixel centers, in other words (0.5, 0.5).
+    *
+    * this is neat but unfortunately not a good way to do things for
+    * triangles with very large values of dadx or dady as it will
+    * result in the subtraction and re-addition from a0 of a very
+    * large number, which means we'll end up loosing a lot of the
+    * fractional bits and precision from a0.  the way to fix this is
+    * to define a0 as the sample at a pixel center somewhere near vmin
+    * instead - i'll switch to this later.
+    */
+   inputs->a0[slot][i] = a0 - (dadx * info->x0_center +
+				   dady * info->y0_center);
+}
+
+
+/**
+ * Compute a0, dadx and dady for a perspective-corrected interpolant,
+ * for a triangle.
+ * We basically multiply the vertex value by 1/w before computing
+ * the plane coefficients (a0, dadx, dady).
+ * Later, when we compute the value at a particular fragment position we'll
+ * divide the interpolated value by the interpolated W at that fragment.
+ */
+static void perspective_coef( struct lp_rast_shader_inputs *inputs,
+                              const struct lp_tri_info *info,
+                              unsigned slot,
+			      unsigned vert_attr,
+                              unsigned i)
+{
+   /* premultiply by 1/w  (v[0][3] is always 1/w):
+    */
+   float a0 = info->v0[vert_attr][i] * info->v0[0][3];
+   float a1 = info->v1[vert_attr][i] * info->v1[0][3];
+   float a2 = info->v2[vert_attr][i] * info->v2[0][3];
+   float da01 = a0 - a1;
+   float da20 = a2 - a0;
+   float dadx = da01 * info->dy20_ooa - info->dy01_ooa * da20;
+   float dady = da20 * info->dx01_ooa - info->dx20_ooa * da01;
+
+   inputs->dadx[slot][i] = dadx;
+   inputs->dady[slot][i] = dady;
+   inputs->a0[slot][i] = a0 - (dadx * info->x0_center +
+				   dady * info->y0_center);
+}
+
+
+/**
+ * Special coefficient setup for gl_FragCoord.
+ * X and Y are trivial
+ * Z and W are copied from position_coef which should have already been computed.
+ * We could do a bit less work if we'd examine gl_FragCoord's swizzle mask.
+ */
+static void
+setup_fragcoord_coef(struct lp_rast_shader_inputs *inputs,
+                     const struct lp_tri_info *info,
+                     unsigned slot,
+                     unsigned usage_mask)
+{
+   /*X*/
+   if (usage_mask & TGSI_WRITEMASK_X) {
+      inputs->a0[slot][0] = 0.0;
+      inputs->dadx[slot][0] = 1.0;
+      inputs->dady[slot][0] = 0.0;
+   }
+
+   /*Y*/
+   if (usage_mask & TGSI_WRITEMASK_Y) {
+      inputs->a0[slot][1] = 0.0;
+      inputs->dadx[slot][1] = 0.0;
+      inputs->dady[slot][1] = 1.0;
+   }
+
+   /*Z*/
+   if (usage_mask & TGSI_WRITEMASK_Z) {
+      linear_coef(inputs, info, slot, 0, 2);
+   }
+
+   /*W*/
+   if (usage_mask & TGSI_WRITEMASK_W) {
+      linear_coef(inputs, info, slot, 0, 3);
+   }
+}
+
+
+/**
+ * Setup the fragment input attribute with the front-facing value.
+ * \param frontface  is the triangle front facing?
+ */
+static void setup_facing_coef( struct lp_rast_shader_inputs *inputs,
+                               unsigned slot,
+                               boolean frontface,
+                               unsigned usage_mask)
+{
+   /* convert TRUE to 1.0 and FALSE to -1.0 */
+   if (usage_mask & TGSI_WRITEMASK_X)
+      constant_coef( inputs, slot, 2.0f * frontface - 1.0f, 0 );
+
+   if (usage_mask & TGSI_WRITEMASK_Y)
+      constant_coef( inputs, slot, 0.0f, 1 ); /* wasted */
+
+   if (usage_mask & TGSI_WRITEMASK_Z)
+      constant_coef( inputs, slot, 0.0f, 2 ); /* wasted */
+
+   if (usage_mask & TGSI_WRITEMASK_W)
+      constant_coef( inputs, slot, 0.0f, 3 ); /* wasted */
+}
+
+
+/**
+ * Compute the tri->coef[] array dadx, dady, a0 values.
+ */
+void lp_setup_tri_coef( struct lp_setup_context *setup,
+			struct lp_rast_shader_inputs *inputs,
+			const struct lp_tri_info *info)
+{
+   unsigned fragcoord_usage_mask = TGSI_WRITEMASK_XYZ;
+   unsigned slot;
+   unsigned i;
+
+   /* setup interpolation for all the remaining attributes:
+    */
+   for (slot = 0; slot < setup->fs.nr_inputs; slot++) {
+      unsigned vert_attr = setup->fs.input[slot].src_index;
+      unsigned usage_mask = setup->fs.input[slot].usage_mask;
+
+      switch (setup->fs.input[slot].interp) {
+      case LP_INTERP_CONSTANT:
+         if (setup->flatshade_first) {
+            for (i = 0; i < NUM_CHANNELS; i++)
+               if (usage_mask & (1 << i))
+                  constant_coef(inputs, slot+1, info->v0[vert_attr][i], i);
+         }
+         else {
+            for (i = 0; i < NUM_CHANNELS; i++)
+               if (usage_mask & (1 << i))
+                  constant_coef(inputs, slot+1, info->v2[vert_attr][i], i);
+         }
+         break;
+
+      case LP_INTERP_LINEAR:
+         for (i = 0; i < NUM_CHANNELS; i++)
+            if (usage_mask & (1 << i))
+               linear_coef(inputs, info, slot+1, vert_attr, i);
+         break;
+
+      case LP_INTERP_PERSPECTIVE:
+         for (i = 0; i < NUM_CHANNELS; i++)
+            if (usage_mask & (1 << i))
+               perspective_coef(inputs, info, slot+1, vert_attr, i);
+         fragcoord_usage_mask |= TGSI_WRITEMASK_W;
+         break;
+
+      case LP_INTERP_POSITION:
+         /*
+          * The generated pixel interpolators will pick up the coeffs from
+          * slot 0, so all need to ensure that the usage mask is covers all
+          * usages.
+          */
+         fragcoord_usage_mask |= usage_mask;
+         break;
+
+      case LP_INTERP_FACING:
+         setup_facing_coef(inputs, slot+1, info->frontfacing, usage_mask);
+         break;
+
+      default:
+         assert(0);
+      }
+   }
+
+   /* The internal position input is in slot zero:
+    */
+   setup_fragcoord_coef(inputs, info, 0, fragcoord_usage_mask);
+}
+
+#else
+extern void lp_setup_coef_dummy(void);
+void lp_setup_coef_dummy(void)
+{
+}
+
+#endif
diff --git a/src/gallium/drivers/llvmpipe/lp_setup_coef.h b/src/gallium/drivers/llvmpipe/lp_setup_coef.h
new file mode 100644
index 0000000000..d68b39c603
--- /dev/null
+++ b/src/gallium/drivers/llvmpipe/lp_setup_coef.h
@@ -0,0 +1,61 @@
+/**************************************************************************
+ *
+ * Copyright 2010 VMware, Inc.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+
+
+/**
+ * The setup code is concerned with point/line/triangle setup and
+ * putting commands/data into the bins.
+ */
+
+
+#ifndef LP_SETUP_COEF_H
+#define LP_SETUP_COEF_H
+
+
+struct lp_tri_info {
+
+   float x0_center;
+   float y0_center;
+
+   /* turn these into an aligned float[4] */
+   float dy01_ooa;
+   float dy20_ooa;
+   float dx01_ooa;
+   float dx20_ooa;
+
+   const float (*v0)[4];
+   const float (*v1)[4];
+   const float (*v2)[4];
+
+   boolean frontfacing;		/* remove eventually */
+};
+
+void lp_setup_tri_coef( struct lp_setup_context *setup,
+			struct lp_rast_shader_inputs *inputs,
+			const struct lp_tri_info *info);
+
+#endif
diff --git a/src/gallium/drivers/llvmpipe/lp_setup_coef_intrin.c b/src/gallium/drivers/llvmpipe/lp_setup_coef_intrin.c
new file mode 100644
index 0000000000..b477bc2113
--- /dev/null
+++ b/src/gallium/drivers/llvmpipe/lp_setup_coef_intrin.c
@@ -0,0 +1,208 @@
+/**************************************************************************
+ *
+ * Copyright 2010 VMware.
+ * All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sub license, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the
+ * next paragraph) shall be included in all copies or substantial portions
+ * of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
+ * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ **************************************************************************/
+
+/*
+ * Binning code for triangles
+ */
+
+#include "util/u_math.h"
+#include "util/u_memory.h"
+#include "lp_perf.h"
+#include "lp_setup_context.h"
+#include "lp_setup_coef.h"
+#include "lp_rast.h"
+#include "lp_state_fs.h"
+
+#if defined(PIPE_ARCH_SSE)
+#include <emmintrin.h>
+
+
+static void constant_coef4( struct lp_rast_shader_inputs *inputs,
+			    const struct lp_tri_info *info,
+			    unsigned slot,
+			    const float *attr)
+{
+   *(__m128 *)inputs->a0[slot]   = *(__m128 *)attr;
+   *(__m128 *)inputs->dadx[slot] = _mm_set1_ps(0.0);
+   *(__m128 *)inputs->dady[slot] = _mm_set1_ps(0.0);
+}
+
+
+
+/**
+ * Setup the fragment input attribute with the front-facing value.
+ * \param frontface  is the triangle front facing?
+ */
+static void setup_facing_coef( struct lp_rast_shader_inputs *inputs,
+			       const struct lp_tri_info *info,
+			       unsigned slot )
+{
+   /* XXX: just pass frontface directly to the shader, don't bother
+    * treating it as an input.
+    */
+   __m128 a0 = _mm_setr_ps(info->frontfacing ? 1.0 : -1.0,
+			   0, 0, 0);
+
+   *(__m128 *)inputs->a0[slot]   = a0;
+   *(__m128 *)inputs->dadx[slot] = _mm_set1_ps(0.0);
+   *(__m128 *)inputs->dady[slot] = _mm_set1_ps(0.0);
+}
+
+
+
+static void calc_coef4( struct lp_rast_shader_inputs *inputs,
+			const struct lp_tri_info *info,
+			unsigned slot,
+			__m128 a0,
+			__m128 a1,
+			__m128 a2)
+{
+   __m128 da01          = _mm_sub_ps(a0, a1);
+   __m128 da20          = _mm_sub_ps(a2, a0);
+
+   __m128 da01_dy20_ooa = _mm_mul_ps(da01, _mm_set1_ps(info->dy20_ooa));
+   __m128 da20_dy01_ooa = _mm_mul_ps(da20, _mm_set1_ps(info->dy01_ooa));   
+   __m128 dadx          = _mm_sub_ps(da01_dy20_ooa, da20_dy01_ooa);
+
+   __m128 da01_dx20_ooa = _mm_mul_ps(da01, _mm_set1_ps(info->dx20_ooa));
+   __m128 da20_dx01_ooa = _mm_mul_ps(da20, _mm_set1_ps(info->dx01_ooa));
+   __m128 dady          = _mm_sub_ps(da20_dx01_ooa, da01_dx20_ooa);
+
+   __m128 dadx_x0       = _mm_mul_ps(dadx, _mm_set1_ps(info->x0_center));
+   __m128 dady_y0       = _mm_mul_ps(dady, _mm_set1_ps(info->y0_center));
+   __m128 attr_v0       = _mm_add_ps(dadx_x0, dady_y0);
+   __m128 attr_0        = _mm_sub_ps(a0, attr_v0);
+
+   *(__m128 *)inputs->a0[slot]   = attr_0;
+   *(__m128 *)inputs->dadx[slot] = dadx;
+   *(__m128 *)inputs->dady[slot] = dady;
+}
+
+
+static void linear_coef( struct lp_rast_shader_inputs *inputs,
+                         const struct lp_tri_info *info,
+                         unsigned slot,
+                         unsigned vert_attr)
+{
+   __m128 a0 = *(const __m128 *)info->v0[vert_attr];
+   __m128 a1 = *(const __m128 *)info->v1[vert_attr];
+   __m128 a2 = *(const __m128 *)info->v2[vert_attr];
+
+   calc_coef4(inputs, info, slot, a0, a1, a2);
+}
+
+
+
+/**
+ * Compute a0, dadx and dady for a perspective-corrected interpolant,
+ * for a triangle.
+ * We basically multiply the vertex value by 1/w before computing
+ * the plane coefficients (a0, dadx, dady).
+ * Later, when we compute the value at a particular fragment position we'll
+ * divide the interpolated value by the interpolated W at that fragment.
+ */
+static void perspective_coef( struct lp_rast_shader_inputs *inputs,
+                              const struct lp_tri_info *info,
+                              unsigned slot,
+			      unsigned vert_attr)
+{
+   /* premultiply by 1/w  (v[0][3] is always 1/w):
+    */
+   __m128 a0 = *(const __m128 *)info->v0[vert_attr];
+   __m128 a1 = *(const __m128 *)info->v1[vert_attr];
+   __m128 a2 = *(const __m128 *)info->v2[vert_attr];
+
+   __m128 a0_oow = _mm_mul_ps(a0, _mm_set1_ps(info->v0[0][3]));
+   __m128 a1_oow = _mm_mul_ps(a1, _mm_set1_ps(info->v1[0][3]));
+   __m128 a2_oow = _mm_mul_ps(a2, _mm_set1_ps(info->v2[0][3]));
+
+   calc_coef4(inputs, info, slot, a0_oow, a1_oow, a2_oow);
+}
+
+
+
+
+
+/**
+ * Compute the inputs-> dadx, dady, a0 values.
+ */
+void lp_setup_tri_coef( struct lp_setup_context *setup,
+			struct lp_rast_shader_inputs *inputs,
+			const struct lp_tri_info *info)
+{
+   unsigned slot;
+
+   /* The internal position input is in slot zero:
+    */
+   linear_coef(inputs, info, 0, 0);
+
+   /* setup interpolation for all the remaining attributes:
+    */
+   for (slot = 0; slot < setup->fs.nr_inputs; slot++) {
+      unsigned vert_attr = setup->fs.input[slot].src_index;
+
+      switch (setup->fs.input[slot].interp) {
+      case LP_INTERP_CONSTANT:
+         if (setup->flatshade_first) {
+	    constant_coef4(inputs, info, slot+1, info->v0[vert_attr]);
+         }
+         else {
+	    constant_coef4(inputs, info, slot+1, info->v2[vert_attr]);
+         }
+         break;
+
+      case LP_INTERP_LINEAR:
+	 linear_coef(inputs, info, slot+1, vert_attr);
+         break;
+
+      case LP_INTERP_PERSPECTIVE:
+	 perspective_coef(inputs, info, slot+1, vert_attr);
+         break;
+
+      case LP_INTERP_POSITION:
+         /*
+          * The generated pixel interpolators will pick up the coeffs from
+          * slot 0.
+          */
+         break;
+
+      case LP_INTERP_FACING:
+         setup_facing_coef(inputs, info, slot+1);
+         break;
+
+      default:
+         assert(0);
+      }
+   }
+}
+
+#else
+extern void lp_setup_coef_dummy(void);
+void lp_setup_coef_dummy(void)
+{
+}
+#endif
diff --git a/src/gallium/drivers/llvmpipe/lp_setup_tri.c b/src/gallium/drivers/llvmpipe/lp_setup_tri.c
index fe5c9358dd..d86fb8652a 100644
--- a/src/gallium/drivers/llvmpipe/lp_setup_tri.c
+++ b/src/gallium/drivers/llvmpipe/lp_setup_tri.c
@@ -34,33 +34,12 @@
 #include "util/u_rect.h"
 #include "lp_perf.h"
 #include "lp_setup_context.h"
+#include "lp_setup_coef.h"
 #include "lp_rast.h"
 #include "lp_state_fs.h"
 
 #define NUM_CHANNELS 4
 
-struct tri_info {
-
-   float pixel_offset;
-
-   /* fixed point vertex coordinates */
-   int x[3];
-   int y[3];
-
-   /* float x,y deltas - all from the original coordinates
-    */
-   float dy01, dy20;
-   float dx01, dx20;
-   float oneoverarea;
-
-   const float (*v0)[4];
-   const float (*v1)[4];
-   const float (*v2)[4];
-
-   boolean frontfacing;
-};
-
-
 
    
 static INLINE int
@@ -77,247 +56,6 @@ fixed_to_float(int a)
 
 
 
-/**
- * Compute a0 for a constant-valued coefficient (GL_FLAT shading).
- */
-static void constant_coef( struct lp_rast_triangle *tri,
-                           unsigned slot,
-			   const float value,
-                           unsigned i )
-{
-   tri->inputs.a0[slot][i] = value;
-   tri->inputs.dadx[slot][i] = 0.0f;
-   tri->inputs.dady[slot][i] = 0.0f;
-}
-
-
-
-static void linear_coef( struct lp_rast_triangle *tri,
-                         const struct tri_info *info,
-                         unsigned slot,
-                         unsigned vert_attr,
-                         unsigned i)
-{
-   float a0 = info->v0[vert_attr][i];
-   float a1 = info->v1[vert_attr][i];
-   float a2 = info->v2[vert_attr][i];
-
-   float da01 = a0 - a1;
-   float da20 = a2 - a0;
-   float dadx = (da01 * info->dy20 - info->dy01 * da20) * info->oneoverarea;
-   float dady = (da20 * info->dx01 - info->dx20 * da01) * info->oneoverarea;
-
-   tri->inputs.dadx[slot][i] = dadx;
-   tri->inputs.dady[slot][i] = dady;
-
-   /* calculate a0 as the value which would be sampled for the
-    * fragment at (0,0), taking into account that we want to sample at
-    * pixel centers, in other words (0.5, 0.5).
-    *
-    * this is neat but unfortunately not a good way to do things for
-    * triangles with very large values of dadx or dady as it will
-    * result in the subtraction and re-addition from a0 of a very
-    * large number, which means we'll end up loosing a lot of the
-    * fractional bits and precision from a0.  the way to fix this is
-    * to define a0 as the sample at a pixel center somewhere near vmin
-    * instead - i'll switch to this later.
-    */
-   tri->inputs.a0[slot][i] = (a0 -
-                              (dadx * (info->v0[0][0] - info->pixel_offset) +
-                               dady * (info->v0[0][1] - info->pixel_offset)));
-}
-
-
-/**
- * Compute a0, dadx and dady for a perspective-corrected interpolant,
- * for a triangle.
- * We basically multiply the vertex value by 1/w before computing
- * the plane coefficients (a0, dadx, dady).
- * Later, when we compute the value at a particular fragment position we'll
- * divide the interpolated value by the interpolated W at that fragment.
- */
-static void perspective_coef( struct lp_rast_triangle *tri,
-                              const struct tri_info *info,
-                              unsigned slot,
-			      unsigned vert_attr,
-                              unsigned i)
-{
-   /* premultiply by 1/w  (v[0][3] is always 1/w):
-    */
-   float a0 = info->v0[vert_attr][i] * info->v0[0][3];
-   float a1 = info->v1[vert_attr][i] * info->v1[0][3];
-   float a2 = info->v2[vert_attr][i] * info->v2[0][3];
-   float da01 = a0 - a1;
-   float da20 = a2 - a0;
-   float dadx = (da01 * info->dy20 - info->dy01 * da20) * info->oneoverarea;
-   float dady = (da20 * info->dx01 - info->dx20 * da01) * info->oneoverarea;
-
-   tri->inputs.dadx[slot][i] = dadx;
-   tri->inputs.dady[slot][i] = dady;
-   tri->inputs.a0[slot][i] = (a0 -
-                              (dadx * (info->v0[0][0] - info->pixel_offset) +
-                               dady * (info->v0[0][1] - info->pixel_offset)));
-}
-
-
-/**
- * Special coefficient setup for gl_FragCoord.
- * X and Y are trivial
- * Z and W are copied from position_coef which should have already been computed.
- * We could do a bit less work if we'd examine gl_FragCoord's swizzle mask.
- */
-static void
-setup_fragcoord_coef(struct lp_rast_triangle *tri,
-                     const struct tri_info *info,
-                     unsigned slot,
-                     unsigned usage_mask)
-{
-   /*X*/
-   if (usage_mask & TGSI_WRITEMASK_X) {
-      tri->inputs.a0[slot][0] = 0.0;
-      tri->inputs.dadx[slot][0] = 1.0;
-      tri->inputs.dady[slot][0] = 0.0;
-   }
-
-   /*Y*/
-   if (usage_mask & TGSI_WRITEMASK_Y) {
-      tri->inputs.a0[slot][1] = 0.0;
-      tri->inputs.dadx[slot][1] = 0.0;
-      tri->inputs.dady[slot][1] = 1.0;
-   }
-
-   /*Z*/
-   if (usage_mask & TGSI_WRITEMASK_Z) {
-      linear_coef(tri, info, slot, 0, 2);
-   }
-
-   /*W*/
-   if (usage_mask & TGSI_WRITEMASK_W) {
-      linear_coef(tri, info, slot, 0, 3);
-   }
-}
-
-
-/**
- * Setup the fragment input attribute with the front-facing value.
- * \param frontface  is the triangle front facing?
- */
-static void setup_facing_coef( struct lp_rast_triangle *tri,
-                               unsigned slot,
-                               boolean frontface,
-                               unsigned usage_mask)
-{
-   /* convert TRUE to 1.0 and FALSE to -1.0 */
-   if (usage_mask & TGSI_WRITEMASK_X)
-      constant_coef( tri, slot, 2.0f * frontface - 1.0f, 0 );
-
-   if (usage_mask & TGSI_WRITEMASK_Y)
-      constant_coef( tri, slot, 0.0f, 1 ); /* wasted */
-
-   if (usage_mask & TGSI_WRITEMASK_Z)
-      constant_coef( tri, slot, 0.0f, 2 ); /* wasted */
-
-   if (usage_mask & TGSI_WRITEMASK_W)
-      constant_coef( tri, slot, 0.0f, 3 ); /* wasted */
-}
-
-
-/**
- * Compute the tri->coef[] array dadx, dady, a0 values.
- */
-static void setup_tri_coefficients( struct lp_setup_context *setup,
-				    struct lp_rast_triangle *tri,
-                                    const struct tri_info *info)
-{
-   unsigned fragcoord_usage_mask = TGSI_WRITEMASK_XYZ;
-   unsigned slot;
-   unsigned i;
-
-   /* setup interpolation for all the remaining attributes:
-    */
-   for (slot = 0; slot < setup->fs.nr_inputs; slot++) {
-      unsigned vert_attr = setup->fs.input[slot].src_index;
-      unsigned usage_mask = setup->fs.input[slot].usage_mask;
-
-      switch (setup->fs.input[slot].interp) {
-      case LP_INTERP_CONSTANT:
-         if (setup->flatshade_first) {
-            for (i = 0; i < NUM_CHANNELS; i++)
-               if (usage_mask & (1 << i))
-                  constant_coef(tri, slot+1, info->v0[vert_attr][i], i);
-         }
-         else {
-            for (i = 0; i < NUM_CHANNELS; i++)
-               if (usage_mask & (1 << i))
-                  constant_coef(tri, slot+1, info->v2[vert_attr][i], i);
-         }
-         break;
-
-      case LP_INTERP_LINEAR:
-         for (i = 0; i < NUM_CHANNELS; i++)
-            if (usage_mask & (1 << i))
-               linear_coef(tri, info, slot+1, vert_attr, i);
-         break;
-
-      case LP_INTERP_PERSPECTIVE:
-         for (i = 0; i < NUM_CHANNELS; i++)
-            if (usage_mask & (1 << i))
-               perspective_coef(tri, info, slot+1, vert_attr, i);
-         fragcoord_usage_mask |= TGSI_WRITEMASK_W;
-         break;
-
-      case LP_INTERP_POSITION:
-         /*
-          * The generated pixel interpolators will pick up the coeffs from
-          * slot 0, so all need to ensure that the usage mask is covers all
-          * usages.
-          */
-         fragcoord_usage_mask |= usage_mask;
-         break;
-
-      case LP_INTERP_FACING:
-         setup_facing_coef(tri, slot+1, info->frontfacing, usage_mask);
-         break;
-
-      default:
-         assert(0);
-      }
-   }
-
-   /* The internal position input is in slot zero:
-    */
-   setup_fragcoord_coef(tri, info, 0, fragcoord_usage_mask);
-
-   if (0) {
-      for (i = 0; i < NUM_CHANNELS; i++) {
-         float a0   = tri->inputs.a0  [0][i];
-         float dadx = tri->inputs.dadx[0][i];
-         float dady = tri->inputs.dady[0][i];
-
-         debug_printf("POS.%c: a0 = %f, dadx = %f, dady = %f\n",
-                      "xyzw"[i],
-                      a0, dadx, dady);
-      }
-
-      for (slot = 0; slot < setup->fs.nr_inputs; slot++) {
-         unsigned usage_mask = setup->fs.input[slot].usage_mask;
-         for (i = 0; i < NUM_CHANNELS; i++) {
-            if (usage_mask & (1 << i)) {
-               float a0   = tri->inputs.a0  [1 + slot][i];
-               float dadx = tri->inputs.dadx[1 + slot][i];
-               float dady = tri->inputs.dady[1 + slot][i];
-
-               debug_printf("IN[%u].%c: a0 = %f, dadx = %f, dady = %f\n",
-                            slot,
-                            "xyzw"[i],
-                            a0, dadx, dady);
-            }
-         }
-      }
-   }
-}
-
-
 
 
 
@@ -440,16 +178,21 @@ lp_rast_cmd lp_rast_tri_tab[8] = {
  */
 static void
 do_triangle_ccw(struct lp_setup_context *setup,
+		const float (*v0)[4],
 		const float (*v1)[4],
 		const float (*v2)[4],
-		const float (*v3)[4],
 		boolean frontfacing )
 {
 
    struct lp_scene *scene = lp_setup_get_current_scene(setup);
    struct lp_fragment_shader_variant *variant = setup->fs.current.variant;
    struct lp_rast_triangle *tri;
-   struct tri_info info;
+   int x[3];
+   int y[3];
+   float dy01, dy20;
+   float dx01, dx20;
+   float oneoverarea;
+   struct lp_tri_info info;
    int area;
    struct u_rect bbox;
    int ix0, ix1, iy0, iy1;
@@ -458,7 +201,7 @@ do_triangle_ccw(struct lp_setup_context *setup,
    int nr_planes = 3;
       
    if (0)
-      lp_setup_print_triangle(setup, v1, v2, v3);
+      lp_setup_print_triangle(setup, v0, v1, v2);
 
    if (setup->scissor_test) {
       nr_planes = 7;
@@ -468,13 +211,12 @@ do_triangle_ccw(struct lp_setup_context *setup,
    }
 
    /* x/y positions in fixed point */
-   info.x[0] = subpixel_snap(v1[0][0] - setup->pixel_offset);
-   info.x[1] = subpixel_snap(v2[0][0] - setup->pixel_offset);
-   info.x[2] = subpixel_snap(v3[0][0] - setup->pixel_offset);
-   info.y[0] = subpixel_snap(v1[0][1] - setup->pixel_offset);
-   info.y[1] = subpixel_snap(v2[0][1] - setup->pixel_offset);
-   info.y[2] = subpixel_snap(v3[0][1] - setup->pixel_offset);
-
+   x[0] = subpixel_snap(v0[0][0] - setup->pixel_offset);
+   x[1] = subpixel_snap(v1[0][0] - setup->pixel_offset);
+   x[2] = subpixel_snap(v2[0][0] - setup->pixel_offset);
+   y[0] = subpixel_snap(v0[0][1] - setup->pixel_offset);
+   y[1] = subpixel_snap(v1[0][1] - setup->pixel_offset);
+   y[2] = subpixel_snap(v2[0][1] - setup->pixel_offset);
 
 
    /* Bounding rectangle (in pixels) */
@@ -486,10 +228,10 @@ do_triangle_ccw(struct lp_setup_context *setup,
        */
       int adj = (setup->pixel_offset != 0) ? 1 : 0;
 
-      bbox.x0 = (MIN3(info.x[0], info.x[1], info.x[2]) + (FIXED_ONE-1)) >> FIXED_ORDER;
-      bbox.x1 = (MAX3(info.x[0], info.x[1], info.x[2]) + (FIXED_ONE-1)) >> FIXED_ORDER;
-      bbox.y0 = (MIN3(info.y[0], info.y[1], info.y[2]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
-      bbox.y1 = (MAX3(info.y[0], info.y[1], info.y[2]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
+      bbox.x0 = (MIN3(x[0], x[1], x[2]) + (FIXED_ONE-1)) >> FIXED_ORDER;
+      bbox.x1 = (MAX3(x[0], x[1], x[2]) + (FIXED_ONE-1)) >> FIXED_ORDER;
+      bbox.y0 = (MIN3(y[0], y[1], y[2]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
+      bbox.y1 = (MAX3(y[0], y[1], y[2]) + (FIXED_ONE-1) + adj) >> FIXED_ORDER;
 
       /* Inclusive coordinates:
        */
@@ -520,21 +262,21 @@ do_triangle_ccw(struct lp_setup_context *setup,
       return;
 
 #ifdef DEBUG
-   tri->v[0][0] = v1[0][0];
-   tri->v[1][0] = v2[0][0];
-   tri->v[2][0] = v3[0][0];
-   tri->v[0][1] = v1[0][1];
-   tri->v[1][1] = v2[0][1];
-   tri->v[2][1] = v3[0][1];
+   tri->v[0][0] = v0[0][0];
+   tri->v[1][0] = v1[0][0];
+   tri->v[2][0] = v2[0][0];
+   tri->v[0][1] = v0[0][1];
+   tri->v[1][1] = v1[0][1];
+   tri->v[2][1] = v2[0][1];
 #endif
 
-   tri->plane[0].dcdy = info.x[0] - info.x[1];
-   tri->plane[1].dcdy = info.x[1] - info.x[2];
-   tri->plane[2].dcdy = info.x[2] - info.x[0];
+   tri->plane[0].dcdy = x[0] - x[1];
+   tri->plane[1].dcdy = x[1] - x[2];
+   tri->plane[2].dcdy = x[2] - x[0];
 
-   tri->plane[0].dcdx = info.y[0] - info.y[1];
-   tri->plane[1].dcdx = info.y[1] - info.y[2];
-   tri->plane[2].dcdx = info.y[2] - info.y[0];
+   tri->plane[0].dcdx = y[0] - y[1];
+   tri->plane[1].dcdx = y[1] - y[2];
+   tri->plane[2].dcdx = y[2] - y[0];
 
    area = (tri->plane[0].dcdy * tri->plane[2].dcdx -
            tri->plane[2].dcdy * tri->plane[0].dcdx);
@@ -554,20 +296,26 @@ do_triangle_ccw(struct lp_setup_context *setup,
 
    /* 
     */
-   info.pixel_offset = setup->pixel_offset;
-   info.v0 = v1;
-   info.v1 = v2;
-   info.v2 = v3;
-   info.dx01 = info.v0[0][0] - info.v1[0][0];
-   info.dx20 = info.v2[0][0] - info.v0[0][0];
-   info.dy01 = info.v0[0][1] - info.v1[0][1];
-   info.dy20 = info.v2[0][1] - info.v0[0][1];
-   info.oneoverarea = 1.0f / (info.dx01 * info.dy20 - info.dx20 * info.dy01);
+   dx01 = v0[0][0] - v1[0][0];
+   dy01 = v0[0][1] - v1[0][1];
+   dx20 = v2[0][0] - v0[0][0];
+   dy20 = v2[0][1] - v0[0][1];
+   oneoverarea = 1.0f / (dx01 * dy20 - dx20 * dy01);
+
+   info.v0 = v0;
+   info.v1 = v1;
+   info.v2 = v2;
    info.frontfacing = frontfacing;
+   info.x0_center = v0[0][0] - setup->pixel_offset;
+   info.y0_center = v0[0][1] - setup->pixel_offset;
+   info.dx01_ooa  = dx01 * oneoverarea;
+   info.dx20_ooa  = dx20 * oneoverarea;
+   info.dy01_ooa  = dy01 * oneoverarea;
+   info.dy20_ooa  = dy20 * oneoverarea;
 
    /* Setup parameter interpolants:
     */
-   setup_tri_coefficients( setup, tri, &info );
+   lp_setup_tri_coef( setup, &tri->inputs, &info );
 
    tri->inputs.facing = frontfacing ? 1.0F : -1.0F;
    tri->inputs.state = setup->fs.stored;
@@ -580,7 +328,7 @@ do_triangle_ccw(struct lp_setup_context *setup,
       /* half-edge constants, will be interated over the whole render
        * target.
        */
-      plane->c = plane->dcdx * info.x[i] - plane->dcdy * info.y[i];
+      plane->c = plane->dcdx * x[i] - plane->dcdy * y[i];
 
       /* correct for top-left vs. bottom-left fill convention.  
        *