i965/vec4: Simplify opt_reduce_swizzle() using the swizzle utils.
[mesa.git] / src / mesa / drivers / dri / i965 / intel_mipmap_tree.c
index 411e721ce353eaeb807838f8481be722241b703e..eb226d516177af679dcf1a377d4bf87fd1079232 100644 (file)
@@ -29,7 +29,6 @@
 #include <GL/internal/dri_interface.h>
 
 #include "intel_batchbuffer.h"
-#include "intel_chipset.h"
 #include "intel_mipmap_tree.h"
 #include "intel_resolve_map.h"
 #include "intel_tex.h"
@@ -232,7 +231,8 @@ intel_miptree_create_layout(struct brw_context *brw,
                             GLuint height0,
                             GLuint depth0,
                             bool for_bo,
-                            GLuint num_samples)
+                            GLuint num_samples,
+                            bool force_all_slices_at_each_lod)
 {
    struct intel_mipmap_tree *mt = calloc(sizeof(*mt), 1);
    if (!mt)
@@ -290,7 +290,28 @@ intel_miptree_create_layout(struct brw_context *brw,
       /* Adjust width/height/depth for MSAA */
       mt->msaa_layout = compute_msaa_layout(brw, format, mt->target);
       if (mt->msaa_layout == INTEL_MSAA_LAYOUT_IMS) {
-         /* In the Sandy Bridge PRM, volume 4, part 1, page 31, it says:
+         /* From the Ivybridge PRM, Volume 1, Part 1, page 108:
+          * "If the surface is multisampled and it is a depth or stencil
+          *  surface or Multisampled Surface StorageFormat in SURFACE_STATE is
+          *  MSFMT_DEPTH_STENCIL, WL and HL must be adjusted as follows before
+          *  proceeding:
+          *
+          *  +----------------------------------------------------------------+
+          *  | Num Multisamples |        W_l =         |        H_l =         |
+          *  +----------------------------------------------------------------+
+          *  |         2        | ceiling(W_l / 2) * 4 | H_l (no adjustment)  |
+          *  |         4        | ceiling(W_l / 2) * 4 | ceiling(H_l / 2) * 4 |
+          *  |         8        | ceiling(W_l / 2) * 8 | ceiling(H_l / 2) * 4 |
+          *  |        16        | ceiling(W_l / 2) * 8 | ceiling(H_l / 2) * 8 |
+          *  +----------------------------------------------------------------+
+          * "
+          *
+          * Note that MSFMT_DEPTH_STENCIL just means the IMS (interleaved)
+          * format rather than UMS/CMS (array slices).  The Sandybridge PRM,
+          * Volume 1, Part 1, Page 111 has the same formula for 4x MSAA.
+          *
+          * Another more complicated explanation for these adjustments comes
+          * from the Sandybridge PRM, volume 4, part 1, page 31:
           *
           *     "Any of the other messages (sample*, LOD, load4) used with a
           *      (4x) multisampled surface will in-effect sample a surface with
@@ -378,6 +399,7 @@ intel_miptree_create_layout(struct brw_context *brw,
        _mesa_get_format_base_format(format) == GL_DEPTH_STENCIL &&
        (brw->must_use_separate_stencil ||
        (brw->has_separate_stencil && brw_is_hiz_depth_format(brw, format)))) {
+      const bool force_all_slices_at_each_lod = brw->gen == 6;
       mt->stencil_mt = intel_miptree_create(brw,
                                             mt->target,
                                             MESA_FORMAT_S_UINT8,
@@ -388,7 +410,8 @@ intel_miptree_create_layout(struct brw_context *brw,
                                             mt->logical_depth0,
                                             true,
                                             num_samples,
-                                            INTEL_MIPTREE_TILING_ANY);
+                                            INTEL_MIPTREE_TILING_ANY,
+                                            force_all_slices_at_each_lod);
       if (!mt->stencil_mt) {
         intel_miptree_release(&mt);
         return NULL;
@@ -406,6 +429,9 @@ intel_miptree_create_layout(struct brw_context *brw,
       }
    }
 
+   if (force_all_slices_at_each_lod)
+      mt->array_layout = ALL_SLICES_AT_EACH_LOD;
+
    brw_miptree_layout(brw, mt);
 
    return mt;
@@ -462,6 +488,13 @@ intel_miptree_choose_tiling(struct brw_context *brw,
        base_format == GL_DEPTH_STENCIL_EXT)
       return I915_TILING_Y;
 
+   /* 1D textures (and 1D array textures) don't get any benefit from tiling,
+    * in fact it leads to a less efficient use of memory space and bandwidth
+    * due to tile alignment.
+    */
+   if (mt->logical_height0 == 1)
+      return I915_TILING_NONE;
+
    int minimum_pitch = mt->total_width * mt->cpp;
 
    /* If the width is much smaller than a tile, don't bother tiling. */
@@ -482,10 +515,10 @@ intel_miptree_choose_tiling(struct brw_context *brw,
    /* From the Sandybridge PRM, Volume 1, Part 2, page 32:
     * "NOTE: 128BPE Format Color Buffer ( render target ) MUST be either TileX
     *  or Linear."
-    * 128 bits per pixel translates to 16 bytes per pixel.  This is necessary
-    * all the way back to 965, but is explicitly permitted on Gen7.
+    * 128 bits per pixel translates to 16 bytes per pixel. This is necessary
+    * all the way back to 965, but is permitted on Gen7+.
     */
-   if (brw->gen != 7 && mt->cpp >= 16)
+   if (brw->gen < 7 && mt->cpp >= 16)
       return I915_TILING_X;
 
    /* From the Ivy Bridge PRM, Vol4 Part1 2.12.2.1 (SURFACE_STATE for most
@@ -560,7 +593,8 @@ intel_miptree_create(struct brw_context *brw,
                     GLuint depth0,
                     bool expect_accelerated_upload,
                      GLuint num_samples,
-                     enum intel_miptree_tiling_mode requested_tiling)
+                     enum intel_miptree_tiling_mode requested_tiling,
+                     bool force_all_slices_at_each_lod)
 {
    struct intel_mipmap_tree *mt;
    mesa_format tex_format = format;
@@ -574,7 +608,8 @@ intel_miptree_create(struct brw_context *brw,
    mt = intel_miptree_create_layout(brw, target, format,
                                      first_level, last_level, width0,
                                      height0, depth0,
-                                     false, num_samples);
+                                    false, num_samples,
+                                    force_all_slices_at_each_lod);
    /*
     * pitch == 0 || height == 0  indicates the null texture
     */
@@ -614,10 +649,10 @@ intel_miptree_create(struct brw_context *brw,
    mt->pitch = pitch;
 
    /* If the BO is too large to fit in the aperture, we need to use the
-    * BLT engine to support it.  The BLT paths can't currently handle Y-tiling,
-    * so we need to fall back to X.
+    * BLT engine to support it.  Prior to Sandybridge, the BLT paths can't
+    * handle Y-tiling, so we need to fall back to X.
     */
-   if (y_or_x && mt->bo->size >= brw->max_gtt_map_object_size) {
+   if (brw->gen < 6 && y_or_x && mt->bo->size >= brw->max_gtt_map_object_size) {
       perf_debug("%dx%d miptree larger than aperture; falling back to X-tiled\n",
                  mt->total_width, mt->total_height);
 
@@ -664,10 +699,12 @@ intel_miptree_create_for_bo(struct brw_context *brw,
                             uint32_t offset,
                             uint32_t width,
                             uint32_t height,
+                            uint32_t depth,
                             int pitch)
 {
    struct intel_mipmap_tree *mt;
    uint32_t tiling, swizzle;
+   GLenum target;
 
    drm_intel_bo_get_tiling(bo, &tiling, &swizzle);
 
@@ -682,10 +719,12 @@ intel_miptree_create_for_bo(struct brw_context *brw,
     */
    assert(pitch >= 0);
 
-   mt = intel_miptree_create_layout(brw, GL_TEXTURE_2D, format,
+   target = depth > 1 ? GL_TEXTURE_2D_ARRAY : GL_TEXTURE_2D;
+
+   mt = intel_miptree_create_layout(brw, target, format,
                                     0, 0,
-                                    width, height, 1,
-                                    true, 0 /* num_samples */);
+                                    width, height, depth,
+                                    true, 0, false);
    if (!mt) {
       free(mt);
       return mt;
@@ -735,6 +774,7 @@ intel_update_winsys_renderbuffer_miptree(struct brw_context *intel,
                                                  0,
                                                  width,
                                                  height,
+                                                 1,
                                                  pitch);
    if (!singlesample_mt)
       goto fail;
@@ -794,7 +834,7 @@ intel_miptree_create_for_renderbuffer(struct brw_context *brw,
 
    mt = intel_miptree_create(brw, target, format, 0, 0,
                             width, height, depth, true, num_samples,
-                             INTEL_MIPTREE_TILING_ANY);
+                             INTEL_MIPTREE_TILING_ANY, false);
    if (!mt)
       goto fail;
 
@@ -843,7 +883,13 @@ intel_miptree_release(struct intel_mipmap_tree **mt)
 
       drm_intel_bo_unreference((*mt)->bo);
       intel_miptree_release(&(*mt)->stencil_mt);
-      intel_miptree_release(&(*mt)->hiz_mt);
+      if ((*mt)->hiz_buf) {
+         if ((*mt)->hiz_buf->mt)
+            intel_miptree_release(&(*mt)->hiz_buf->mt);
+         else
+            drm_intel_bo_unreference((*mt)->hiz_buf->bo);
+         free((*mt)->hiz_buf);
+      }
       intel_miptree_release(&(*mt)->mcs_mt);
       intel_resolve_map_clear(&(*mt)->hiz_map);
 
@@ -1104,7 +1150,7 @@ intel_miptree_copy_slice_sw(struct brw_context *brw,
                             int height)
 {
    void *src, *dst;
-   int src_stride, dst_stride;
+   ptrdiff_t src_stride, dst_stride;
    int cpp = dst_mt->cpp;
 
    intel_miptree_map(brw, src_mt,
@@ -1122,7 +1168,7 @@ intel_miptree_copy_slice_sw(struct brw_context *brw,
                      BRW_MAP_DIRECT_BIT,
                      &dst, &dst_stride);
 
-   DBG("sw blit %s mt %p %p/%d -> %s mt %p %p/%d (%dx%d)\n",
+   DBG("sw blit %s mt %p %p/%"PRIdPTR" -> %s mt %p %p/%"PRIdPTR" (%dx%d)\n",
        _mesa_get_format_name(src_mt->format),
        src_mt, src, src_stride,
        _mesa_get_format_name(dst_mt->format),
@@ -1237,7 +1283,12 @@ intel_miptree_copy_teximage(struct brw_context *brw,
       intel_texture_object(intelImage->base.Base.TexObject);
    int level = intelImage->base.Base.Level;
    int face = intelImage->base.Base.Face;
-   GLuint depth = intelImage->base.Base.Depth;
+
+   GLuint depth;
+   if (intel_obj->base.Target == GL_TEXTURE_1D_ARRAY)
+      depth = intelImage->base.Base.Height;
+   else
+      depth = intelImage->base.Base.Depth;
 
    if (!invalidate) {
       for (int slice = 0; slice < depth; slice++) {
@@ -1295,7 +1346,8 @@ intel_miptree_alloc_mcs(struct brw_context *brw,
                                      mt->logical_depth0,
                                      true,
                                      0 /* num_samples */,
-                                     INTEL_MIPTREE_TILING_Y);
+                                     INTEL_MIPTREE_TILING_Y,
+                                     false);
 
    /* From the Ivy Bridge PRM, Vol 2 Part 1 p326:
     *
@@ -1352,7 +1404,8 @@ intel_miptree_alloc_non_msrt_mcs(struct brw_context *brw,
                                      mt->logical_depth0,
                                      true,
                                      0 /* num_samples */,
-                                     INTEL_MIPTREE_TILING_Y);
+                                     INTEL_MIPTREE_TILING_Y,
+                                     false);
 
    return mt->mcs_mt;
 }
@@ -1368,7 +1421,7 @@ intel_miptree_level_enable_hiz(struct brw_context *brw,
                                struct intel_mipmap_tree *mt,
                                uint32_t level)
 {
-   assert(mt->hiz_mt);
+   assert(mt->hiz_buf);
 
    if (brw->gen >= 8 || brw->is_haswell) {
       uint32_t width = minify(mt->physical_width0, level);
@@ -1392,25 +1445,253 @@ intel_miptree_level_enable_hiz(struct brw_context *brw,
 }
 
 
+/**
+ * Helper for intel_miptree_alloc_hiz() that determines the required hiz
+ * buffer dimensions and allocates a bo for the hiz buffer.
+ */
+static struct intel_miptree_aux_buffer *
+intel_gen7_hiz_buf_create(struct brw_context *brw,
+                          struct intel_mipmap_tree *mt)
+{
+   unsigned z_width = mt->logical_width0;
+   unsigned z_height = mt->logical_height0;
+   const unsigned z_depth = MAX2(mt->logical_depth0, 1);
+   unsigned hz_width, hz_height;
+   struct intel_miptree_aux_buffer *buf = calloc(sizeof(*buf), 1);
+
+   if (!buf)
+      return NULL;
+
+   /* Gen7 PRM Volume 2, Part 1, 11.5.3 "Hierarchical Depth Buffer" documents
+    * adjustments required for Z_Height and Z_Width based on multisampling.
+    */
+   switch (mt->num_samples) {
+   case 0:
+   case 1:
+      break;
+   case 2:
+   case 4:
+      z_width *= 2;
+      z_height *= 2;
+      break;
+   case 8:
+      z_width *= 4;
+      z_height *= 2;
+      break;
+   default:
+      unreachable("unsupported sample count");
+   }
+
+   const unsigned vertical_align = 8; /* 'j' in the docs */
+   const unsigned H0 = z_height;
+   const unsigned h0 = ALIGN(H0, vertical_align);
+   const unsigned h1 = ALIGN(minify(H0, 1), vertical_align);
+   const unsigned Z0 = z_depth;
+
+   /* HZ_Width (bytes) = ceiling(Z_Width / 16) * 16 */
+   hz_width = ALIGN(z_width, 16);
+
+   if (mt->target == GL_TEXTURE_3D) {
+      unsigned H_i = H0;
+      unsigned Z_i = Z0;
+      hz_height = 0;
+      for (int level = mt->first_level; level <= mt->last_level; ++level) {
+         unsigned h_i = ALIGN(H_i, vertical_align);
+         /* sum(i=0 to m; h_i * max(1, floor(Z_Depth/2**i))) */
+         hz_height += h_i * Z_i;
+         H_i = minify(H_i, 1);
+         Z_i = minify(Z_i, 1);
+      }
+      /* HZ_Height =
+       *    (1/2) * sum(i=0 to m; h_i * max(1, floor(Z_Depth/2**i)))
+       */
+      hz_height = DIV_ROUND_UP(hz_height, 2);
+   } else {
+      const unsigned hz_qpitch = h0 + h1 + (12 * vertical_align);
+      if (mt->target == GL_TEXTURE_CUBE_MAP_ARRAY ||
+          mt->target == GL_TEXTURE_CUBE_MAP) {
+         /* HZ_Height (rows) = Ceiling ( ( Q_pitch * Z_depth * 6/2) /8 ) * 8 */
+         hz_height = DIV_ROUND_UP(hz_qpitch * Z0 * 6, 2 * 8) * 8;
+      } else {
+         /* HZ_Height (rows) = Ceiling ( ( Q_pitch * Z_depth/2) /8 ) * 8 */
+         hz_height = DIV_ROUND_UP(hz_qpitch * Z0, 2 * 8) * 8;
+      }
+   }
+
+   unsigned long pitch;
+   uint32_t tiling = I915_TILING_Y;
+   buf->bo = drm_intel_bo_alloc_tiled(brw->bufmgr, "hiz",
+                                      hz_width, hz_height, 1,
+                                      &tiling, &pitch,
+                                      BO_ALLOC_FOR_RENDER);
+   if (!buf->bo) {
+      free(buf);
+      return NULL;
+   } else if (tiling != I915_TILING_Y) {
+      drm_intel_bo_unreference(buf->bo);
+      free(buf);
+      return NULL;
+   }
+
+   buf->pitch = pitch;
+
+   return buf;
+}
+
+
+/**
+ * Helper for intel_miptree_alloc_hiz() that determines the required hiz
+ * buffer dimensions and allocates a bo for the hiz buffer.
+ */
+static struct intel_miptree_aux_buffer *
+intel_gen8_hiz_buf_create(struct brw_context *brw,
+                          struct intel_mipmap_tree *mt)
+{
+   unsigned z_width = mt->logical_width0;
+   unsigned z_height = mt->logical_height0;
+   const unsigned z_depth = MAX2(mt->logical_depth0, 1);
+   unsigned hz_width, hz_height;
+   struct intel_miptree_aux_buffer *buf = calloc(sizeof(*buf), 1);
+
+   if (!buf)
+      return NULL;
+
+   /* Gen7 PRM Volume 2, Part 1, 11.5.3 "Hierarchical Depth Buffer" documents
+    * adjustments required for Z_Height and Z_Width based on multisampling.
+    */
+   switch (mt->num_samples) {
+   case 0:
+   case 1:
+      break;
+   case 2:
+   case 4:
+      z_width *= 2;
+      z_height *= 2;
+      break;
+   case 8:
+      z_width *= 4;
+      z_height *= 2;
+      break;
+   default:
+      unreachable("unsupported sample count");
+   }
+
+   const unsigned vertical_align = 8; /* 'j' in the docs */
+   const unsigned H0 = z_height;
+   const unsigned h0 = ALIGN(H0, vertical_align);
+   const unsigned h1 = ALIGN(minify(H0, 1), vertical_align);
+   const unsigned Z0 = z_depth;
+
+   /* HZ_Width (bytes) = ceiling(Z_Width / 16) * 16 */
+   hz_width = ALIGN(z_width, 16);
+
+   unsigned H_i = H0;
+   unsigned Z_i = Z0;
+   unsigned sum_h_i = 0;
+   unsigned hz_height_3d_sum = 0;
+   for (int level = mt->first_level; level <= mt->last_level; ++level) {
+      unsigned i = level - mt->first_level;
+      unsigned h_i = ALIGN(H_i, vertical_align);
+      /* sum(i=2 to m; h_i) */
+      if (i >= 2) {
+         sum_h_i += h_i;
+      }
+      /* sum(i=0 to m; h_i * max(1, floor(Z_Depth/2**i))) */
+      hz_height_3d_sum += h_i * Z_i;
+      H_i = minify(H_i, 1);
+      Z_i = minify(Z_i, 1);
+   }
+   /* HZ_QPitch = h0 + max(h1, sum(i=2 to m; h_i)) */
+   buf->qpitch = h0 + MAX2(h1, sum_h_i);
+
+   if (mt->target == GL_TEXTURE_3D) {
+      /* (1/2) * sum(i=0 to m; h_i * max(1, floor(Z_Depth/2**i))) */
+      hz_height = DIV_ROUND_UP(hz_height_3d_sum, 2);
+   } else {
+      /* HZ_Height (rows) = ceiling( (HZ_QPitch/2)/8) *8 * Z_Depth */
+      hz_height = DIV_ROUND_UP(buf->qpitch, 2 * 8) * 8 * Z0;
+      if (mt->target == GL_TEXTURE_CUBE_MAP_ARRAY ||
+          mt->target == GL_TEXTURE_CUBE_MAP) {
+         /* HZ_Height (rows) = ceiling( (HZ_QPitch/2)/8) *8 * 6 * Z_Depth
+          *
+          * We can can just take our hz_height calculation from above, and
+          * multiply by 6 for the cube map and cube map array types.
+          */
+         hz_height *= 6;
+      }
+   }
+
+   unsigned long pitch;
+   uint32_t tiling = I915_TILING_Y;
+   buf->bo = drm_intel_bo_alloc_tiled(brw->bufmgr, "hiz",
+                                      hz_width, hz_height, 1,
+                                      &tiling, &pitch,
+                                      BO_ALLOC_FOR_RENDER);
+   if (!buf->bo) {
+      free(buf);
+      return NULL;
+   } else if (tiling != I915_TILING_Y) {
+      drm_intel_bo_unreference(buf->bo);
+      free(buf);
+      return NULL;
+   }
+
+   buf->pitch = pitch;
+
+   return buf;
+}
+
+
+static struct intel_miptree_aux_buffer *
+intel_hiz_miptree_buf_create(struct brw_context *brw,
+                             struct intel_mipmap_tree *mt)
+{
+   struct intel_miptree_aux_buffer *buf = calloc(sizeof(*buf), 1);
+   const bool force_all_slices_at_each_lod = brw->gen == 6;
+
+   if (!buf)
+      return NULL;
+
+   buf->mt = intel_miptree_create(brw,
+                                  mt->target,
+                                  mt->format,
+                                  mt->first_level,
+                                  mt->last_level,
+                                  mt->logical_width0,
+                                  mt->logical_height0,
+                                  mt->logical_depth0,
+                                  true,
+                                  mt->num_samples,
+                                  INTEL_MIPTREE_TILING_ANY,
+                                  force_all_slices_at_each_lod);
+   if (!buf->mt) {
+      free(buf);
+      return NULL;
+   }
+
+   buf->bo = buf->mt->bo;
+   buf->pitch = buf->mt->pitch;
+   buf->qpitch = buf->mt->qpitch;
+
+   return buf;
+}
+
 
 bool
 intel_miptree_alloc_hiz(struct brw_context *brw,
                        struct intel_mipmap_tree *mt)
 {
-   assert(mt->hiz_mt == NULL);
-   mt->hiz_mt = intel_miptree_create(brw,
-                                     mt->target,
-                                     mt->format,
-                                     mt->first_level,
-                                     mt->last_level,
-                                     mt->logical_width0,
-                                     mt->logical_height0,
-                                     mt->logical_depth0,
-                                     true,
-                                     mt->num_samples,
-                                     INTEL_MIPTREE_TILING_ANY);
+   assert(mt->hiz_buf == NULL);
+
+   if (brw->gen == 7) {
+      mt->hiz_buf = intel_gen7_hiz_buf_create(brw, mt);
+   } else if (brw->gen >= 8) {
+      mt->hiz_buf = intel_gen8_hiz_buf_create(brw, mt);
+   } else {
+      mt->hiz_buf = intel_hiz_miptree_buf_create(brw, mt);
+   }
 
-   if (!mt->hiz_mt)
+   if (!mt->hiz_buf)
       return false;
 
    /* Mark that all slices need a HiZ resolve. */
@@ -1665,8 +1946,8 @@ intel_miptree_updownsample(struct brw_context *brw,
 {
    if (brw->gen < 8) {
       brw_blorp_blit_miptrees(brw,
-                              src, 0 /* level */, 0 /* layer */,
-                              dst, 0 /* level */, 0 /* layer */,
+                              src, 0 /* level */, 0 /* layer */, src->format,
+                              dst, 0 /* level */, 0 /* layer */, dst->format,
                               0, 0,
                               src->logical_width0, src->logical_height0,
                               0, 0,
@@ -1686,7 +1967,9 @@ intel_miptree_updownsample(struct brw_context *brw,
 
       brw_blorp_blit_miptrees(brw,
                               src->stencil_mt, 0 /* level */, 0 /* layer */,
+                              src->stencil_mt->format,
                               dst->stencil_mt, 0 /* level */, 0 /* layer */,
+                              dst->stencil_mt->format,
                               0, 0,
                               src->logical_width0, src->logical_height0,
                               0, 0,
@@ -1732,8 +2015,8 @@ intel_miptree_map_gtt(struct brw_context *brw,
    unsigned int bw, bh;
    void *base;
    unsigned int image_x, image_y;
-   int x = map->x;
-   int y = map->y;
+   intptr_t x = map->x;
+   intptr_t y = map->y;
 
    /* For compressed formats, the stride is the number of bytes per
     * row of blocks.  intel_miptree_get_image_offset() already does
@@ -1759,7 +2042,8 @@ intel_miptree_map_gtt(struct brw_context *brw,
       map->ptr = base + y * map->stride + x * mt->cpp;
    }
 
-   DBG("%s: %d,%d %dx%d from mt %p (%s) %d,%d = %p/%d\n", __FUNCTION__,
+   DBG("%s: %d,%d %dx%d from mt %p (%s) "
+       "%"PRIiPTR",%"PRIiPTR" = %p/%d\n", __FUNCTION__,
        map->x, map->y, map->w, map->h,
        mt, _mesa_get_format_name(mt->format),
        x, y, map->ptr, map->stride);
@@ -1785,21 +2069,29 @@ intel_miptree_map_blit(struct brw_context *brw,
                                   0, 0,
                                   map->w, map->h, 1,
                                   false, 0,
-                                  INTEL_MIPTREE_TILING_NONE);
+                                  INTEL_MIPTREE_TILING_NONE,
+                                  false);
    if (!map->mt) {
       fprintf(stderr, "Failed to allocate blit temporary\n");
       goto fail;
    }
    map->stride = map->mt->pitch;
 
-   if (!intel_miptree_blit(brw,
-                           mt, level, slice,
-                           map->x, map->y, false,
-                           map->mt, 0, 0,
-                           0, 0, false,
-                           map->w, map->h, GL_COPY)) {
-      fprintf(stderr, "Failed to blit\n");
-      goto fail;
+   /* One of either READ_BIT or WRITE_BIT or both is set.  READ_BIT implies no
+    * INVALIDATE_RANGE_BIT.  WRITE_BIT needs the original values read in unless
+    * invalidate is set, since we'll be writing the whole rectangle from our
+    * temporary buffer back out.
+    */
+   if (!(map->mode & GL_MAP_INVALIDATE_RANGE_BIT)) {
+      if (!intel_miptree_blit(brw,
+                              mt, level, slice,
+                              map->x, map->y, false,
+                              map->mt, 0, 0,
+                              0, 0, false,
+                              map->w, map->h, GL_COPY)) {
+         fprintf(stderr, "Failed to blit\n");
+         goto fail;
+      }
    }
 
    map->ptr = intel_miptree_map_raw(brw, map->mt);
@@ -2238,12 +2530,52 @@ can_blit_slice(struct intel_mipmap_tree *mt,
    if (image_x >= 32768 || image_y >= 32768)
       return false;
 
+   /* See intel_miptree_blit() for details on the 32k pitch limit. */
    if (mt->pitch >= 32768)
       return false;
 
    return true;
 }
 
+static bool
+use_intel_mipree_map_blit(struct brw_context *brw,
+                          struct intel_mipmap_tree *mt,
+                          GLbitfield mode,
+                          unsigned int level,
+                          unsigned int slice)
+{
+   if (brw->has_llc &&
+      /* It's probably not worth swapping to the blit ring because of
+       * all the overhead involved.
+       */
+       !(mode & GL_MAP_WRITE_BIT) &&
+       !mt->compressed &&
+       (mt->tiling == I915_TILING_X ||
+        /* Prior to Sandybridge, the blitter can't handle Y tiling */
+        (brw->gen >= 6 && mt->tiling == I915_TILING_Y)) &&
+       can_blit_slice(mt, level, slice))
+      return true;
+
+   if (mt->tiling != I915_TILING_NONE &&
+       mt->bo->size >= brw->max_gtt_map_object_size) {
+      assert(can_blit_slice(mt, level, slice));
+      return true;
+   }
+
+   return false;
+}
+
+/**
+ * Parameter \a out_stride has type ptrdiff_t not because the buffer stride may
+ * exceed 32 bits but to diminish the likelihood subtle bugs in pointer
+ * arithmetic overflow.
+ *
+ * If you call this function and use \a out_stride, then you're doing pointer
+ * arithmetic on \a out_ptr. The type of \a out_stride doesn't prevent all
+ * bugs.  The caller must still take care to avoid 32-bit overflow errors in
+ * all arithmetic expressions that contain buffer offsets and pixel sizes,
+ * which usually have type uint32_t or GLuint.
+ */
 void
 intel_miptree_map(struct brw_context *brw,
                   struct intel_mipmap_tree *mt,
@@ -2255,7 +2587,7 @@ intel_miptree_map(struct brw_context *brw,
                   unsigned int h,
                   GLbitfield mode,
                   void **out_ptr,
-                  int *out_stride)
+                  ptrdiff_t *out_stride)
 {
    struct intel_miptree_map *map;
 
@@ -2280,18 +2612,7 @@ intel_miptree_map(struct brw_context *brw,
       intel_miptree_map_etc(brw, mt, map, level, slice);
    } else if (mt->stencil_mt && !(mode & BRW_MAP_DIRECT_BIT)) {
       intel_miptree_map_depthstencil(brw, mt, map, level, slice);
-   }
-   /* See intel_miptree_blit() for details on the 32k pitch limit. */
-   else if (brw->has_llc &&
-            !(mode & GL_MAP_WRITE_BIT) &&
-            !mt->compressed &&
-            (mt->tiling == I915_TILING_X ||
-             (brw->gen >= 6 && mt->tiling == I915_TILING_Y)) &&
-            can_blit_slice(mt, level, slice)) {
-      intel_miptree_map_blit(brw, mt, map, level, slice);
-   } else if (mt->tiling != I915_TILING_NONE &&
-              mt->bo->size >= brw->max_gtt_map_object_size) {
-      assert(can_blit_slice(mt, level, slice));
+   } else if (use_intel_mipree_map_blit(brw, mt, mode, level, slice)) {
       intel_miptree_map_blit(brw, mt, map, level, slice);
 #if defined(USE_SSE41)
    } else if (!(mode & GL_MAP_WRITE_BIT) && !mt->compressed && cpu_has_sse4_1) {