Initial import.

1 files changed, 1797 insertions, 0 deletions

diff --git a/src/mesa/swrast/s_depth.c b/src/mesa/swrast/s_depth.c
new file mode 100644
index 0000000..34897ba
--- /dev/null
+++ b/src/mesa/swrast/s_depth.c
@@ -0,0 +1,1797 @@
+/*
+ * Mesa 3-D graphics library
+ * Version:  5.1
+ *
+ * Copyright (C) 1999-2003  Brian Paul   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, sublicense,
+ * 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 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 NONINFRINGEMENT.  IN NO EVENT SHALL
+ * BRIAN PAUL 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.
+ */
+
+
+#include "glheader.h"
+#include "context.h"
+#include "macros.h"
+#include "imports.h"
+
+#include "s_depth.h"
+#include "s_context.h"
+
+
+/**
+ * Return address of depth buffer value for given window coord.
+ */
+GLvoid *
+_swrast_zbuffer_address(GLcontext *ctx, GLint x, GLint y)
+{
+   if (ctx->Visual.depthBits <= 16)
+      return (GLushort *) ctx->DrawBuffer->DepthBuffer
+         + ctx->DrawBuffer->Width * y + x;
+   else
+      return (GLuint *) ctx->DrawBuffer->DepthBuffer
+         + ctx->DrawBuffer->Width * y + x;
+}
+
+
+#define Z_ADDRESS16( CTX, X, Y )				\
+            ( ((GLushort *) (CTX)->DrawBuffer->DepthBuffer)	\
+              + (CTX)->DrawBuffer->Width * (Y) + (X) )
+
+#define Z_ADDRESS32( CTX, X, Y )				\
+            ( ((GLuint *) (CTX)->DrawBuffer->DepthBuffer)	\
+              + (CTX)->DrawBuffer->Width * (Y) + (X) )
+
+
+
+/**********************************************************************/
+/*****                   Depth Testing Functions                  *****/
+/**********************************************************************/
+
+
+/*
+ * Do depth test for an array of fragments.  This is used both for
+ * software and hardware Z buffers.
+ * Input:  zbuffer - array of z values in the zbuffer
+ *         z - array of fragment z values
+ * Return:  number of fragments which pass the test.
+ */
+static GLuint
+depth_test_span16( GLcontext *ctx, GLuint n,
+                   GLushort zbuffer[], const GLdepth z[], GLubyte mask[] )
+{
+   GLuint passed = 0;
+
+   /* switch cases ordered from most frequent to less frequent */
+   switch (ctx->Depth.Func) {
+      case GL_LESS:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] < zbuffer[i]) {
+		     /* pass */
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] < zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_LEQUAL:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] <= zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] <= zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GEQUAL:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] >= zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] >= zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GREATER:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] > zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] > zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_NOTEQUAL:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] != zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] != zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_EQUAL:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] == zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] == zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_ALWAYS:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  zbuffer[i] = z[i];
+		  passed++;
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer or mask */
+	    passed = n;
+	 }
+	 break;
+      case GL_NEVER:
+         _mesa_bzero(mask, n * sizeof(GLubyte));
+	 break;
+      default:
+         _mesa_problem(ctx, "Bad depth func in depth_test_span16");
+   }
+
+   return passed;
+}
+
+
+static GLuint
+depth_test_span32( GLcontext *ctx, GLuint n,
+                   GLuint zbuffer[], const GLdepth z[], GLubyte mask[] )
+{
+   GLuint passed = 0;
+
+   /* switch cases ordered from most frequent to less frequent */
+   switch (ctx->Depth.Func) {
+      case GL_LESS:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] < zbuffer[i]) {
+		     /* pass */
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] < zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_LEQUAL:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] <= zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] <= zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GEQUAL:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] >= zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] >= zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GREATER:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] > zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] > zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_NOTEQUAL:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] != zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] != zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_EQUAL:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] == zbuffer[i]) {
+		     zbuffer[i] = z[i];
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  if (z[i] == zbuffer[i]) {
+		     /* pass */
+		     passed++;
+		  }
+		  else {
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_ALWAYS:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0;i<n;i++) {
+	       if (mask[i]) {
+		  zbuffer[i] = z[i];
+		  passed++;
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer or mask */
+	    passed = n;
+	 }
+	 break;
+      case GL_NEVER:
+         _mesa_bzero(mask, n * sizeof(GLubyte));
+	 break;
+      default:
+         _mesa_problem(ctx, "Bad depth func in depth_test_span32");
+   }
+
+   return passed;
+}
+
+
+
+/*
+ * Apply depth test to span of fragments.  Hardware or software z buffer.
+ */
+static GLuint
+depth_test_span( GLcontext *ctx, struct sw_span *span)
+{
+   const GLint x = span->x;
+   const GLint y = span->y;
+   const GLuint n = span->end;
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+
+   ASSERT((span->arrayMask & SPAN_XY) == 0);
+   ASSERT(span->arrayMask & SPAN_Z);
+   
+   if (swrast->Driver.ReadDepthSpan) {
+      /* hardware-based depth buffer */
+      GLdepth zbuffer[MAX_WIDTH];
+      GLuint passed;
+      (*swrast->Driver.ReadDepthSpan)(ctx, n, x, y, zbuffer);
+      passed = depth_test_span32(ctx, n, zbuffer, span->array->z,
+                                 span->array->mask);
+      ASSERT(swrast->Driver.WriteDepthSpan);
+      (*swrast->Driver.WriteDepthSpan)(ctx, n, x, y, zbuffer,
+                                       span->array->mask);
+      if (passed < n)
+         span->writeAll = GL_FALSE;
+      return passed;
+   }
+   else {
+      GLuint passed;
+      /* software depth buffer */
+      if (ctx->Visual.depthBits <= 16) {
+         GLushort *zptr = (GLushort *) Z_ADDRESS16(ctx, x, y);
+         passed = depth_test_span16(ctx, n, zptr, span->array->z, span->array->mask);
+      }
+      else {
+         GLuint *zptr = (GLuint *) Z_ADDRESS32(ctx, x, y);
+         passed = depth_test_span32(ctx, n, zptr, span->array->z, span->array->mask);
+      }
+#if 1
+      if (passed < span->end) {
+         span->writeAll = GL_FALSE;
+      }
+#else
+      /* this causes a glDrawPixels(GL_DEPTH_COMPONENT) conformance failure */
+      if (passed < span->end) {
+	  span->writeAll = GL_FALSE;
+	  if (passed == 0) {
+	      span->end = 0;
+	      return 0;
+	  }
+	  while (span->end > 0  &&  span->mask[span->end - 1] == 0)
+	      span->end --;
+      }
+#endif
+      return passed;
+   }
+}
+
+
+
+
+/*
+ * Do depth testing for an array of fragments using software Z buffer.
+ */
+static void
+software_depth_test_pixels16( GLcontext *ctx, GLuint n,
+                              const GLint x[], const GLint y[],
+                              const GLdepth z[], GLubyte mask[] )
+{
+   /* switch cases ordered from most frequent to less frequent */
+   switch (ctx->Depth.Func) {
+      case GL_LESS:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] < *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] < *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_LEQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] <= *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] <= *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GEQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] >= *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] >= *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GREATER:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] > *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] > *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_NOTEQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] != *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] != *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_EQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] == *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  if (z[i] == *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_ALWAYS:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLushort *zptr = Z_ADDRESS16(ctx,x[i],y[i]);
+		  *zptr = z[i];
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer or mask */
+	 }
+	 break;
+      case GL_NEVER:
+	 /* depth test never passes */
+         _mesa_bzero(mask, n * sizeof(GLubyte));
+	 break;
+      default:
+         _mesa_problem(ctx, "Bad depth func in software_depth_test_pixels");
+   }
+}
+
+
+
+/*
+ * Do depth testing for an array of fragments using software Z buffer.
+ */
+static void
+software_depth_test_pixels32( GLcontext *ctx, GLuint n,
+                              const GLint x[], const GLint y[],
+                              const GLdepth z[], GLubyte mask[] )
+{
+   /* switch cases ordered from most frequent to less frequent */
+   switch (ctx->Depth.Func) {
+      case GL_LESS:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] < *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] < *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_LEQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] <= *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] <= *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GEQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] >= *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] >= *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GREATER:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] > *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] > *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_NOTEQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] != *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] != *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_EQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] == *zptr) {
+		     /* pass */
+		     *zptr = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  if (z[i] == *zptr) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_ALWAYS:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  GLuint *zptr = Z_ADDRESS32(ctx,x[i],y[i]);
+		  *zptr = z[i];
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer or mask */
+	 }
+	 break;
+      case GL_NEVER:
+	 /* depth test never passes */
+         _mesa_bzero(mask, n * sizeof(GLubyte));
+	 break;
+      default:
+         _mesa_problem(ctx, "Bad depth func in software_depth_test_pixels");
+   }
+}
+
+
+
+/*
+ * Do depth testing for an array of pixels using hardware Z buffer.
+ * Input/output:  zbuffer - array of depth values from Z buffer
+ * Input:  z - array of fragment z values.
+ */
+static void
+hardware_depth_test_pixels( GLcontext *ctx, GLuint n, GLdepth zbuffer[],
+                            const GLdepth z[], GLubyte mask[] )
+{
+   /* switch cases ordered from most frequent to less frequent */
+   switch (ctx->Depth.Func) {
+      case GL_LESS:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] < zbuffer[i]) {
+		     /* pass */
+		     zbuffer[i] = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] < zbuffer[i]) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_LEQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] <= zbuffer[i]) {
+		     /* pass */
+		     zbuffer[i] = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] <= zbuffer[i]) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GEQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] >= zbuffer[i]) {
+		     /* pass */
+		     zbuffer[i] = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] >= zbuffer[i]) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_GREATER:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] > zbuffer[i]) {
+		     /* pass */
+		     zbuffer[i] = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] > zbuffer[i]) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_NOTEQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] != zbuffer[i]) {
+		     /* pass */
+		     zbuffer[i] = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] != zbuffer[i]) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_EQUAL:
+         if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] == zbuffer[i]) {
+		     /* pass */
+		     zbuffer[i] = z[i];
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  if (z[i] == zbuffer[i]) {
+		     /* pass */
+		  }
+		  else {
+		     /* fail */
+		     mask[i] = 0;
+		  }
+	       }
+	    }
+	 }
+	 break;
+      case GL_ALWAYS:
+	 if (ctx->Depth.Mask) {
+	    /* Update Z buffer */
+            GLuint i;
+	    for (i=0; i<n; i++) {
+	       if (mask[i]) {
+		  zbuffer[i] = z[i];
+	       }
+	    }
+	 }
+	 else {
+	    /* Don't update Z buffer or mask */
+	 }
+	 break;
+      case GL_NEVER:
+	 /* depth test never passes */
+         _mesa_bzero(mask, n * sizeof(GLubyte));
+	 break;
+      default:
+         _mesa_problem(ctx, "Bad depth func in hardware_depth_test_pixels");
+   }
+}
+
+
+
+static GLuint
+depth_test_pixels( GLcontext *ctx, struct sw_span *span )
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   const GLuint n = span->end;
+   const GLint *x = span->array->x;
+   const GLint *y = span->array->y;
+   const GLdepth *z = span->array->z;
+   GLubyte *mask = span->array->mask;
+
+   if (swrast->Driver.ReadDepthPixels) {
+      /* read depth values from hardware Z buffer */
+      GLdepth zbuffer[MAX_WIDTH];
+      (*swrast->Driver.ReadDepthPixels)(ctx, n, x, y, zbuffer);
+
+      hardware_depth_test_pixels( ctx, n, zbuffer, z, mask );
+
+      /* update hardware Z buffer with new values */
+      assert(swrast->Driver.WriteDepthPixels);
+      (*swrast->Driver.WriteDepthPixels)(ctx, n, x, y, zbuffer, mask );
+   }
+   else {
+      /* software depth testing */
+      if (ctx->Visual.depthBits <= 16)
+         software_depth_test_pixels16(ctx, n, x, y, z, mask);
+      else
+         software_depth_test_pixels32(ctx, n, x, y, z, mask);
+   }
+   return n; /* not really correct, but OK */
+}
+
+
+/**
+ * Apply depth (Z) buffer testing to the span.
+ * \return approx number of pixels that passed (only zero is reliable)
+ */
+GLuint
+_swrast_depth_test_span( GLcontext *ctx, struct sw_span *span)
+{
+   if (span->arrayMask & SPAN_XY)
+      return depth_test_pixels(ctx, span);
+   else
+      return depth_test_span(ctx, span);
+}
+
+
+/**
+ * GL_EXT_depth_bounds_test extension.
+ * Discard fragments depending on whether the corresponding Z-buffer
+ * values are outside the depth bounds test range.
+ * Note: we test the Z buffer values, not the fragment Z values!
+ * \return GL_TRUE if any fragments pass, GL_FALSE if no fragments pass
+ */
+GLboolean
+_swrast_depth_bounds_test( GLcontext *ctx, struct sw_span *span )
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   GLdepth zMin = (GLdepth) (ctx->Depth.BoundsMin * ctx->DepthMaxF + 0.5F);
+   GLdepth zMax = (GLdepth) (ctx->Depth.BoundsMax * ctx->DepthMaxF + 0.5F);
+   GLubyte *mask = span->array->mask;
+   GLuint i;
+   GLboolean anyPass = GL_FALSE;
+
+   if (swrast->Driver.ReadDepthPixels) {
+      /* read depth values from hardware Z buffer */
+      GLdepth zbuffer[MAX_WIDTH];
+      ASSERT(span->end <= MAX_WIDTH);
+      if (span->arrayMask & SPAN_XY)
+         (*swrast->Driver.ReadDepthPixels)(ctx, span->end, span->array->x,
+                                           span->array->y, zbuffer);
+      else
+         (*swrast->Driver.ReadDepthSpan)(ctx, span->end, span->x, span->y,
+                                         zbuffer);
+      for (i = 0; i < span->end; i++) {
+         if (mask[i]) {
+            if (zbuffer[i] < zMin || zbuffer[i] > zMax)
+               mask[i] = GL_FALSE;
+            else
+               anyPass = GL_TRUE;
+         }
+      }
+   }
+   else {
+      /* software Z buffer */
+      if (span->arrayMask & SPAN_XY) {
+         if (ctx->Visual.depthBits <= 16) {
+            /* 16 bits / Z */
+            for (i = 0; i < span->end; i++) {
+               if (mask[i]) {
+                  const GLushort *zPtr = Z_ADDRESS16(ctx, span->array->x[i],
+                                                     span->array->y[i]);
+                  if (*zPtr < zMin || *zPtr > zMax)
+                     mask[i] = GL_FALSE;
+                  else
+                     anyPass = GL_TRUE;
+               }
+            }
+         }
+         else {
+            /* 32 bits / Z */
+            for (i = 0; i < span->end; i++) {
+               if (mask[i]) {
+                  const GLuint *zPtr = Z_ADDRESS32(ctx, span->array->x[i],
+                                                   span->array->y[i]);
+                  if (*zPtr < zMin || *zPtr > zMax)
+                     mask[i] = GL_FALSE;
+                  else
+                     anyPass = GL_TRUE;
+               }
+            }
+         }
+      }
+      else {
+         if (ctx->Visual.depthBits <= 16) {
+            /* 16 bits / Z */
+            const GLushort *zPtr = Z_ADDRESS16(ctx, span->x, span->y);
+            for (i = 0; i < span->end; i++) {
+               if (mask[i]) {
+                  if (zPtr[i] < zMin || zPtr[i] > zMax)
+                     mask[i] = GL_FALSE;
+                  else
+                     anyPass = GL_TRUE;
+               }
+            }
+         }
+         else {
+            /* 32 bits / Z */
+            const GLuint *zPtr = Z_ADDRESS32(ctx, span->x, span->y);
+            for (i = 0; i < span->end; i++) {
+               if (mask[i]) {
+                  if (zPtr[i] < zMin || zPtr[i] > zMax)
+                     mask[i] = GL_FALSE;
+                  else
+                     anyPass = GL_TRUE;
+               }
+            }
+         }
+      }
+   }
+   return anyPass;
+}
+
+
+
+/**********************************************************************/
+/*****                      Read Depth Buffer                     *****/
+/**********************************************************************/
+
+
+/**
+ * Read a span of depth values from the depth buffer.
+ * This function does clipping before calling the device driver function.
+ */
+void
+_swrast_read_depth_span( GLcontext *ctx,
+                       GLint n, GLint x, GLint y, GLdepth depth[] )
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+
+   if (y < 0 || y >= (GLint) ctx->DrawBuffer->Height ||
+       x + (GLint) n <= 0 || x >= (GLint) ctx->DrawBuffer->Width) {
+      /* span is completely outside framebuffer */
+      GLint i;
+      for (i = 0; i < n; i++)
+         depth[i] = 0;
+      return;
+   }
+
+   if (x < 0) {
+      GLint dx = -x;
+      GLint i;
+      for (i = 0; i < dx; i++)
+         depth[i] = 0;
+      x = 0;
+      n -= dx;
+      depth += dx;
+   }
+   if (x + n > (GLint) ctx->DrawBuffer->Width) {
+      GLint dx = x + n - (GLint) ctx->DrawBuffer->Width;
+      GLint i;
+      for (i = 0; i < dx; i++)
+         depth[n - i - 1] = 0;
+      n -= dx;
+   }
+   if (n <= 0) {
+      return;
+   }
+
+   if (ctx->DrawBuffer->DepthBuffer) {
+      /* read from software depth buffer */
+      if (ctx->Visual.depthBits <= 16) {
+         const GLushort *zptr = Z_ADDRESS16( ctx, x, y );
+         GLint i;
+         for (i = 0; i < n; i++) {
+            depth[i] = zptr[i];
+         }
+      }
+      else {
+         const GLuint *zptr = Z_ADDRESS32( ctx, x, y );
+         GLint i;
+         for (i = 0; i < n; i++) {
+            depth[i] = zptr[i];
+         }
+      }
+   }
+   else if (swrast->Driver.ReadDepthSpan) {
+      /* read from hardware depth buffer */
+      (*swrast->Driver.ReadDepthSpan)( ctx, n, x, y, depth );
+   }
+   else {
+      /* no depth buffer */
+      _mesa_bzero(depth, n * sizeof(GLfloat));
+   }
+
+}
+
+
+
+
+/**
+ * Return a span of depth values from the depth buffer as floats in [0,1].
+ * This is used for both hardware and software depth buffers.
+ * Input:  n - how many pixels
+ *         x,y - location of first pixel
+ * Output:  depth - the array of depth values
+ */
+void
+_swrast_read_depth_span_float( GLcontext *ctx,
+                             GLint n, GLint x, GLint y, GLfloat depth[] )
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+   const GLfloat scale = 1.0F / ctx->DepthMaxF;
+
+   if (y < 0 || y >= (GLint) ctx->DrawBuffer->Height ||
+       x + (GLint) n <= 0 || x >= (GLint) ctx->DrawBuffer->Width) {
+      /* span is completely outside framebuffer */
+      GLint i;
+      for (i = 0; i < n; i++)
+         depth[i] = 0.0F;
+      return;
+   }
+
+   if (x < 0) {
+      GLint dx = -x;
+      GLint i;
+      for (i = 0; i < dx; i++)
+         depth[i] = 0.0F;
+      n -= dx;
+      x = 0;
+   }
+   if (x + n > (GLint) ctx->DrawBuffer->Width) {
+      GLint dx = x + n - (GLint) ctx->DrawBuffer->Width;
+      GLint i;
+      for (i = 0; i < dx; i++)
+         depth[n - i - 1] = 0.0F;
+      n -= dx;
+   }
+   if (n <= 0) {
+      return;
+   }
+
+   if (ctx->DrawBuffer->DepthBuffer) {
+      /* read from software depth buffer */
+      if (ctx->Visual.depthBits <= 16) {
+         const GLushort *zptr = Z_ADDRESS16( ctx, x, y );
+         GLint i;
+         for (i = 0; i < n; i++) {
+            depth[i] = (GLfloat) zptr[i] * scale;
+         }
+      }
+      else {
+         const GLuint *zptr = Z_ADDRESS32( ctx, x, y );
+         GLint i;
+         for (i = 0; i < n; i++) {
+            depth[i] = (GLfloat) zptr[i] * scale;
+         }
+      }
+   }
+   else if (swrast->Driver.ReadDepthSpan) {
+      /* read from hardware depth buffer */
+      GLdepth d[MAX_WIDTH];
+      GLint i;
+      assert(n <= MAX_WIDTH);
+      (*swrast->Driver.ReadDepthSpan)( ctx, n, x, y, d );
+      for (i = 0; i < n; i++) {
+	 depth[i] = d[i] * scale;
+      }
+   }
+   else {
+      /* no depth buffer */
+      _mesa_bzero(depth, n * sizeof(GLfloat));
+   }
+}
+
+
+
+/**********************************************************************/
+/*****                Allocate and Clear Depth Buffer             *****/
+/**********************************************************************/
+
+
+
+/**
+ * Allocate a new depth buffer.  If there's already a depth buffer allocated
+ * it will be free()'d.  The new depth buffer will be uniniitalized.
+ * This function is only called through Driver.alloc_depth_buffer.
+ */
+void
+_swrast_alloc_depth_buffer( GLframebuffer *buffer )
+{
+   GLint bytesPerValue;
+
+   ASSERT(buffer->UseSoftwareDepthBuffer);
+
+   /* deallocate current depth buffer if present */
+   if (buffer->DepthBuffer) {
+      MESA_PBUFFER_FREE(buffer->DepthBuffer);
+      buffer->DepthBuffer = NULL;
+   }
+
+   /* allocate new depth buffer, but don't initialize it */
+   if (buffer->Visual.depthBits <= 16)
+      bytesPerValue = sizeof(GLushort);
+   else
+      bytesPerValue = sizeof(GLuint);
+
+   buffer->DepthBuffer = MESA_PBUFFER_ALLOC(buffer->Width * buffer->Height
+                                            * bytesPerValue);
+
+   if (!buffer->DepthBuffer) {
+      /* out of memory */
+      GET_CURRENT_CONTEXT(ctx);
+      if (ctx) {
+         ctx->Depth.Test = GL_FALSE;
+         ctx->NewState |= _NEW_DEPTH;
+         _mesa_error(ctx, GL_OUT_OF_MEMORY, "Couldn't allocate depth buffer");
+      }
+   }
+}
+
+
+/**
+ * Clear the depth buffer.  If the depth buffer doesn't exist yet we'll
+ * allocate it now.
+ * This function is only called through Driver.clear_depth_buffer.
+ */
+void
+_swrast_clear_depth_buffer( GLcontext *ctx )
+{
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
+
+   if (ctx->Visual.depthBits == 0
+       || !ctx->Depth.Mask) {
+      /* no depth buffer, or writing to it is disabled */
+      return;
+   }
+
+   if (swrast->Driver.WriteMonoDepthSpan) {
+      const GLdepth clearValue = (GLdepth)(ctx->Depth.Clear * ctx->DepthMax);
+      const GLint x = ctx->DrawBuffer->_Xmin;
+      const GLint y = ctx->DrawBuffer->_Ymin;
+      const GLint height = ctx->DrawBuffer->_Ymax - ctx->DrawBuffer->_Ymin;
+      const GLint width  = ctx->DrawBuffer->_Xmax - ctx->DrawBuffer->_Xmin;
+      GLint i;
+
+      for (i = 0; i < height; i++) {
+         (*swrast->Driver.WriteMonoDepthSpan)( ctx, width, x, y + i,
+                                               clearValue, NULL );
+      }
+
+      return;
+   }
+
+   if (!ctx->DrawBuffer->DepthBuffer)
+      return;
+
+   /* The loops in this function have been written so the IRIX 5.3
+    * C compiler can unroll them.  Hopefully other compilers can too!
+    */
+
+   if (ctx->Scissor.Enabled) {
+      /* only clear scissor region */
+      if (ctx->Visual.depthBits <= 16) {
+         const GLushort clearValue = (GLushort) (ctx->Depth.Clear * ctx->DepthMax);
+         const GLint rows = ctx->DrawBuffer->_Ymax - ctx->DrawBuffer->_Ymin;
+         const GLint cols = ctx->DrawBuffer->_Xmax - ctx->DrawBuffer->_Xmin;
+         const GLint rowStride = ctx->DrawBuffer->Width;
+         GLushort *dRow = (GLushort *) ctx->DrawBuffer->DepthBuffer
+            + ctx->DrawBuffer->_Ymin * rowStride + ctx->DrawBuffer->_Xmin;
+         GLint i, j;
+         for (i = 0; i < rows; i++) {
+            for (j = 0; j < cols; j++) {
+               dRow[j] = clearValue;
+            }
+            dRow += rowStride;
+         }
+      }
+      else {
+         const GLuint clearValue = (GLuint) (ctx->Depth.Clear * ctx->DepthMax);
+         const GLint rows = ctx->DrawBuffer->_Ymax - ctx->DrawBuffer->_Ymin;
+         const GLint cols = ctx->DrawBuffer->_Xmax - ctx->DrawBuffer->_Xmin;
+         const GLint rowStride = ctx->DrawBuffer->Width;
+         GLuint *dRow = (GLuint *) ctx->DrawBuffer->DepthBuffer
+            + ctx->DrawBuffer->_Ymin * rowStride + ctx->DrawBuffer->_Xmin;
+         GLint i, j;
+         for (i = 0; i < rows; i++) {
+            for (j = 0; j < cols; j++) {
+               dRow[j] = clearValue;
+            }
+            dRow += rowStride;
+         }
+      }
+   }
+   else {
+      /* clear whole buffer */
+      if (ctx->Visual.depthBits <= 16) {
+         const GLushort clearValue = (GLushort) (ctx->Depth.Clear * ctx->DepthMax);
+         if ((clearValue & 0xff) == (clearValue >> 8)) {
+            if (clearValue == 0) {
+               _mesa_bzero(ctx->DrawBuffer->DepthBuffer,
+                     2*ctx->DrawBuffer->Width*ctx->DrawBuffer->Height);
+            }
+            else {
+               /* lower and upper bytes of clear_value are same, use MEMSET */
+               MEMSET( ctx->DrawBuffer->DepthBuffer, clearValue & 0xff,
+                       2 * ctx->DrawBuffer->Width * ctx->DrawBuffer->Height);
+            }
+         }
+         else {
+            GLushort *d = (GLushort *) ctx->DrawBuffer->DepthBuffer;
+            GLint n = ctx->DrawBuffer->Width * ctx->DrawBuffer->Height;
+            while (n >= 16) {
+               d[0] = clearValue;    d[1] = clearValue;
+               d[2] = clearValue;    d[3] = clearValue;
+               d[4] = clearValue;    d[5] = clearValue;
+               d[6] = clearValue;    d[7] = clearValue;
+               d[8] = clearValue;    d[9] = clearValue;
+               d[10] = clearValue;   d[11] = clearValue;
+               d[12] = clearValue;   d[13] = clearValue;
+               d[14] = clearValue;   d[15] = clearValue;
+               d += 16;
+               n -= 16;
+            }
+            while (n > 0) {
+               *d++ = clearValue;
+               n--;
+            }
+         }
+      }
+      else {
+         /* >16 bit depth buffer */
+         const GLuint clearValue = (GLuint) (ctx->Depth.Clear * ctx->DepthMax);
+         if (clearValue == 0) {
+            _mesa_bzero(ctx->DrawBuffer->DepthBuffer,
+                ctx->DrawBuffer->Width*ctx->DrawBuffer->Height*sizeof(GLuint));
+         }
+         else {
+            GLint n = ctx->DrawBuffer->Width * ctx->DrawBuffer->Height;
+            GLuint *d = (GLuint *) ctx->DrawBuffer->DepthBuffer;
+            while (n >= 16) {
+               d[0] = clearValue;    d[1] = clearValue;
+               d[2] = clearValue;    d[3] = clearValue;
+               d[4] = clearValue;    d[5] = clearValue;
+               d[6] = clearValue;    d[7] = clearValue;
+               d[8] = clearValue;    d[9] = clearValue;
+               d[10] = clearValue;   d[11] = clearValue;
+               d[12] = clearValue;   d[13] = clearValue;
+               d[14] = clearValue;   d[15] = clearValue;
+               d += 16;
+               n -= 16;
+            }
+            while (n > 0) {
+               *d++ = clearValue;
+               n--;
+            }
+         }
+      }
+   }
+}