i965: Add GPU BLIT of texture image to PBO in Intel driver

Add Intel driver hook for glGetTexImage to accelerate the case of reading
texture image into a PBO.  This case gets huge performance gains by using
GPU BLIT directly to PBO rather than GPU BLIT to temporary texture followed
by memcpy.

No regressions on Piglit tests  with Intel driver.
Performance gain (1280 x 800 FBO, Ivybridge):
glGetTexImage + glMapBufferRange  with patch 1.45 msec
glGetTexImage + glMapBufferRange without patch 4.68 msec

v3: (by Kenneth Graunke)
 - Fix compile after Eric's change to drop the tiling argument
   to intel_miptree_create_for_bo.
 - Add GL_TEXTURE_3D to blacklisted texture targets to prevent Piglit
   regressions.
 - Squash in several whitespace and coding style fixes.

src/mesa/drivers/dri/i965/intel_tex_image.c

@@ -15,6 +15,8 @@
 #include "main/teximage.h"
 #include "main/texstore.h"
 
+#include "drivers/common/meta.h"
+
 #include "intel_mipmap_tree.h"
 #include "intel_buffer_objects.h"
 #include "intel_batchbuffer.h"
@@ -413,10 +415,118 @@ intel_image_target_texture_2d(struct gl_context *ctx, GLenum target,
                               image->tile_x, image->tile_y);
 }
 
+static bool
+blit_texture_to_pbo(struct gl_context *ctx,
+                    GLenum format, GLenum type,
+                    GLvoid * pixels, struct gl_texture_image *texImage)
+{
+   struct intel_texture_image *intelImage = intel_texture_image(texImage);
+   struct brw_context *brw = brw_context(ctx);
+   const struct gl_pixelstore_attrib *pack = &ctx->Pack;
+   struct intel_buffer_object *dst = intel_buffer_object(pack->BufferObj);
+   GLuint dst_offset;
+   drm_intel_bo *dst_buffer;
+   GLenum target = texImage->TexObject->Target;
+
+   /* Check if we can use GPU blit to copy from the hardware texture
+    * format to the user's format/type.
+    * Note that GL's pixel transfer ops don't apply to glGetTexImage()
+    */
+
+   if (!_mesa_format_matches_format_and_type(intelImage->mt->format, format,
+                                             type, false))
+   {
+      perf_debug("%s: unsupported format, fallback to CPU mapping for PBO\n",
+                 __FUNCTION__);
+
+      return false;
+   }
+
+   if (ctx->_ImageTransferState) {
+      perf_debug("%s: bad transfer state, fallback to CPU mapping for PBO\n",
+                 __FUNCTION__);
+      return false;
+   }
+
+   if (pack->SwapBytes || pack->LsbFirst) {
+      perf_debug("%s: unsupported pack swap params\n",
+                 __FUNCTION__);
+      return false;
+   }
+
+   if (target == GL_TEXTURE_1D_ARRAY ||
+       target == GL_TEXTURE_2D_ARRAY ||
+       target == GL_TEXTURE_CUBE_MAP_ARRAY ||
+       target == GL_TEXTURE_3D) {
+      perf_debug("%s: no support for multiple slices, fallback to CPU mapping "
+                 "for PBO\n", __FUNCTION__);
+      return false;
+   }
+
+   int dst_stride = _mesa_image_row_stride(pack, texImage->Width, format, type);
+   bool dst_flip = false;
+   /* Mesa flips the dst_stride for ctx->Pack.Invert, our mt must have a
+    * normal dst_stride.
+    */
+   struct gl_pixelstore_attrib uninverted_pack = *pack;
+   if (ctx->Pack.Invert) {
+      dst_stride = -dst_stride;
+      dst_flip = true;
+      uninverted_pack.Invert = false;
+   }
+   dst_offset = (GLintptr) pixels;
+   dst_offset += _mesa_image_offset(2, &uninverted_pack, texImage->Width,
+                                    texImage->Height, format, type, 0, 0, 0);
+   dst_buffer = intel_bufferobj_buffer(brw, dst, dst_offset,
+                                       texImage->Height * dst_stride);
+
+   struct intel_mipmap_tree *pbo_mt =
+      intel_miptree_create_for_bo(brw,
+                                  dst_buffer,
+                                  intelImage->mt->format,
+                                  dst_offset,
+                                  texImage->Width, texImage->Height,
+                                  dst_stride);
+
+   if (!pbo_mt)
+      return false;
+
+   if (!intel_miptree_blit(brw,
+                           intelImage->mt, texImage->Level, texImage->Face,
+                           0, 0, false,
+                           pbo_mt, 0, 0,
+                           0, 0, dst_flip,
+                           texImage->Width, texImage->Height, GL_COPY))
+      return false;
+
+   intel_miptree_release(&pbo_mt);
+
+   return true;
+}
+
+static void
+intel_get_tex_image(struct gl_context *ctx,
+                    GLenum format, GLenum type, GLvoid *pixels,
+                    struct gl_texture_image *texImage) {
+   DBG("%s\n", __FUNCTION__);
+
+   if (_mesa_is_bufferobj(ctx->Pack.BufferObj)) {
+      /* Using PBOs, so try the BLT based path. */
+      if (blit_texture_to_pbo(ctx, format, type, pixels, texImage))
+         return;
+
+   }
+
+   _mesa_meta_GetTexImage(ctx, format, type, pixels, texImage);
+
+   DBG("%s - DONE\n", __FUNCTION__);
+}
+
 void
 intelInitTextureImageFuncs(struct dd_function_table *functions)
 {
    functions->TexImage = intelTexImage;
    functions->EGLImageTargetTexture2D = intel_image_target_texture_2d;
    functions->BindRenderbufferTexImage = intel_bind_renderbuffer_tex_image;
+   functions->GetTexImage = intel_get_tex_image;
 }