Implement early depth test.

Early depth test is enabled when depth test is enabled and
alpha test is disabled and fragment shader does not write
depth.
The early-z is implemented by moving the depth test stage
just before the fragment shader stage and prepending it
with an earlyz stage, introduced with this commit.
The earlyz stage prepares the quad->outputs.depth for
the following depth test stage by interpolating Z position,
just as the fragment shader would do.

src/mesa/pipe/softpipe/Makefile

@@ -18,6 +18,7 @@ DRIVER_SOURCES = \
 	sp_quad_colormask.c \
 	sp_quad_coverage.c \
 	sp_quad_depth_test.c \
+	sp_quad_earlyz.c \
 	sp_quad_fs.c \
 	sp_quad_occlusion.c \
 	sp_quad_output.c \

src/mesa/pipe/softpipe/sp_context.c

@@ -161,6 +161,7 @@ static void softpipe_destroy( struct pipe_context *pipe )
    draw_destroy( softpipe->draw );
 
    softpipe->quad.polygon_stipple->destroy( softpipe->quad.polygon_stipple );
+   softpipe->quad.earlyz->destroy( softpipe->quad.earlyz );
    softpipe->quad.shade->destroy( softpipe->quad.shade );
    softpipe->quad.alpha_test->destroy( softpipe->quad.alpha_test );
    softpipe->quad.depth_test->destroy( softpipe->quad.depth_test );
@@ -369,6 +370,7 @@ struct pipe_context *softpipe_create( struct pipe_winsys *pipe_winsys,
 
    /* setup quad rendering stages */
    softpipe->quad.polygon_stipple = sp_quad_polygon_stipple_stage(softpipe);
+   softpipe->quad.earlyz = sp_quad_earlyz_stage(softpipe);
    softpipe->quad.shade = sp_quad_shade_stage(softpipe);
    softpipe->quad.alpha_test = sp_quad_alpha_test_stage(softpipe);
    softpipe->quad.depth_test = sp_quad_depth_test_stage(softpipe);

src/mesa/pipe/softpipe/sp_context.h

@@ -134,6 +134,7 @@ struct softpipe_context {
    /** Software quad rendering pipeline */
    struct {
       struct quad_stage *polygon_stipple;
+      struct quad_stage *earlyz;
       struct quad_stage *shade;
       struct quad_stage *alpha_test;
       struct quad_stage *stencil_test;

src/mesa/pipe/softpipe/sp_quad.c

@@ -28,24 +28,52 @@
 
 #include "sp_context.h"
 
+#include "sp_state.h"
+#include "pipe/tgsi/exec/tgsi_token.h"
 
+static void
+sp_push_quad_first(
+   struct softpipe_context *sp,
+   struct quad_stage       *quad )
+{
+   quad->next = sp->quad.first;
+   sp->quad.first = quad;
+}
+
+static void
+sp_build_depth_stencil(
+   struct softpipe_context *sp )
+{
+   if (sp->depth_stencil->stencil.front_enabled ||
+       sp->depth_stencil->stencil.back_enabled) {
+      sp_push_quad_first( sp, sp->quad.stencil_test );
+   }
+   else if (sp->depth_stencil->depth.enabled &&
+            sp->framebuffer.zbuf) {
+      sp_push_quad_first( sp, sp->quad.depth_test );
+   }
+}
 
 void
 sp_build_quad_pipeline(struct softpipe_context *sp)
 {
+   boolean  early_depth_test =
+               sp->depth_stencil->depth.enabled &&
+               sp->framebuffer.zbuf &&
+               !sp->alpha_test->enabled &&
+               sp->fs->shader.output_semantic_name[0] != TGSI_SEMANTIC_POSITION;
+
    /* build up the pipeline in reverse order... */
 
    sp->quad.first = sp->quad.output;
 
    if (sp->blend->colormask != 0xf) {
-      sp->quad.colormask->next = sp->quad.first;
-      sp->quad.first = sp->quad.colormask;
+      sp_push_quad_first( sp, sp->quad.colormask );
    }
 
    if (sp->blend->blend_enable ||
        sp->blend->logicop_enable) {
-      sp->quad.blend->next = sp->quad.first;
-      sp->quad.first = sp->quad.blend;
+      sp_push_quad_first( sp, sp->quad.blend );
    }
 
    if (sp->framebuffer.num_cbufs == 1) {
@@ -54,46 +82,38 @@ sp_build_quad_pipeline(struct softpipe_context *sp)
    }
    else {
       /* insert bufloop stage */
-      sp->quad.bufloop->next = sp->quad.first;
-      sp->quad.first = sp->quad.bufloop;
+      sp_push_quad_first( sp, sp->quad.bufloop );
    }
 
    if (sp->depth_stencil->depth.occlusion_count) {
-      sp->quad.occlusion->next = sp->quad.first;
-      sp->quad.first = sp->quad.occlusion;
+      sp_push_quad_first( sp, sp->quad.occlusion );
    }
 
    if (sp->rasterizer->poly_smooth ||
        sp->rasterizer->line_smooth ||
        sp->rasterizer->point_smooth) {
-      sp->quad.coverage->next = sp->quad.first;
-      sp->quad.first = sp->quad.coverage;
+      sp_push_quad_first( sp, sp->quad.coverage );
    }
 
-   if (   sp->depth_stencil->stencil.front_enabled
-       || sp->depth_stencil->stencil.back_enabled) {
-      sp->quad.stencil_test->next = sp->quad.first;
-      sp->quad.first = sp->quad.stencil_test;
-   }
-   else if (sp->depth_stencil->depth.enabled &&
-            sp->framebuffer.zbuf) {
-      sp->quad.depth_test->next = sp->quad.first;
-      sp->quad.first = sp->quad.depth_test;
+   if (!early_depth_test) {
+      sp_build_depth_stencil( sp );
    }
 
    if (sp->alpha_test->enabled) {
-      sp->quad.alpha_test->next = sp->quad.first;
-      sp->quad.first = sp->quad.alpha_test;
+      sp_push_quad_first( sp, sp->quad.alpha_test );
    }
 
    /* XXX always enable shader? */
    if (1) {
-      sp->quad.shade->next = sp->quad.first;
-      sp->quad.first = sp->quad.shade;
+      sp_push_quad_first( sp, sp->quad.shade );
+   }
+
+   if (early_depth_test) {
+      sp_build_depth_stencil( sp );
+      sp_push_quad_first( sp, sp->quad.earlyz );
    }
 
    if (sp->rasterizer->poly_stipple_enable) {
-      sp->quad.polygon_stipple->next = sp->quad.first;
-      sp->quad.first = sp->quad.polygon_stipple;
+      sp_push_quad_first( sp, sp->quad.polygon_stipple );
    }
 }

src/mesa/pipe/softpipe/sp_quad.h

@@ -51,6 +51,7 @@ struct quad_stage {
 
 
 struct quad_stage *sp_quad_polygon_stipple_stage( struct softpipe_context *softpipe );
+struct quad_stage *sp_quad_earlyz_stage( struct softpipe_context *softpipe );
 struct quad_stage *sp_quad_shade_stage( struct softpipe_context *softpipe );
 struct quad_stage *sp_quad_alpha_test_stage( struct softpipe_context *softpipe );
 struct quad_stage *sp_quad_stencil_test_stage( struct softpipe_context *softpipe );

src/mesa/pipe/softpipe/sp_quad_earlyz.c

@@ -0,0 +1,100 @@
+/**************************************************************************
+ * 
+ * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
+ * 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 TUNGSTEN GRAPHICS 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.
+ * 
+ **************************************************************************/
+
+/**
+ * \brief  Quad early-z testing
+ */
+
+#include "pipe/p_defines.h"
+#include "pipe/p_util.h"
+#include "sp_context.h"
+#include "sp_headers.h"
+#include "sp_surface.h"
+#include "sp_quad.h"
+#include "sp_tile_cache.h"
+
+static void
+earlyz_quad(
+   struct quad_stage    *qs,
+   struct quad_header   *quad )
+{
+   uint  i;
+   const float fx = (float) quad->x0;
+   const float fy = (float) quad->y0;
+   float xy[4][2];
+
+   xy[0][0] = fx;
+   xy[1][0] = fx + 1.0f;
+   xy[2][0] = fx;
+   xy[3][0] = fx + 1.0f;
+
+   xy[0][1] = fy;
+   xy[1][1] = fy;
+   xy[2][1] = fy + 1.0f;
+   xy[3][1] = fy + 1.0f;
+
+   for (i = 0; i < QUAD_SIZE; i++) {
+      quad->outputs.depth[i] =
+         quad->coef[0].a0[2] +
+         quad->coef[0].dadx[2] * xy[i][0] +
+         quad->coef[0].dady[2] * xy[i][1];
+   }
+
+   if (qs->next) {
+      qs->next->run( qs->next, quad );
+   }
+}
+
+static void
+earlyz_begin(
+   struct quad_stage *qs )
+{
+   if (qs->next) {
+      qs->next->begin( qs->next );
+   }
+}
+
+static void
+earlyz_destroy(
+   struct quad_stage *qs )
+{
+   FREE( qs );
+}
+
+struct quad_stage *
+sp_quad_earlyz_stage(
+   struct softpipe_context *softpipe )
+{
+   struct quad_stage *stage = CALLOC_STRUCT( quad_stage );
+
+   stage->softpipe = softpipe;
+   stage->begin = earlyz_begin;
+   stage->run = earlyz_quad;
+   stage->destroy = earlyz_destroy;
+
+   return stage;
+}