CELL: fixing stencil bugs

These are the defects found and fixed so far.  Several more have
been observed; I'm working on them.

- Fixed an error in spe_load_uint() that caused incorrect values to be
  loaded if the given unsigned value had the low 18 bits as 0,
  and that caused inefficient code to be emitted if the given value
  had the high 14 bits as 0.

- Fixed a problem in stencil code generation where optional registers
  weren't tracked correctly.

- Fixed a problem that the stencil function NEVER was acting as ALWAYS.

- Fixed several problems that could occur if stenciling were enabled but
  depth was disabled.

- Fixed a problem with two-sided stencil writemask handling that could
  cause a stencil writemask to not be applied.

- Fixed several state permutations that were incorrectly flagged as
  not requiring stencil values to be calculated.

1 files changed, 70 insertions, 18 deletions

diff --git a/src/gallium/drivers/cell/ppu/cell_gen_fragment.c b/src/gallium/drivers/cell/ppu/cell_gen_fragment.c
index de170d1036..4e1e53ecdc 100644
--- a/src/gallium/drivers/cell/ppu/cell_gen_fragment.c
+++ b/src/gallium/drivers/cell/ppu/cell_gen_fragment.c
@@ -247,6 +247,7 @@ setup_optional_register(struct spe_function *f, boolean *is_already_set, unsigne
 {
    if (*is_already_set) return;
    *r = spe_allocate_available_register(f);
+   *is_already_set = true;
 }
 
 static inline void
@@ -1157,7 +1158,6 @@ gen_stencil_test(struct spe_function *f, const struct pipe_stencil_state *state,
       /* stencil_pass = mask & (s == reference) */
       spe_compare_equal_uint(f, stencil_pass_reg, fbS_reg, state->ref_value);
       spe_and(f, stencil_pass_reg, mask_reg, stencil_pass_reg);
-      /* stencil_fail = mask & ~stencil_pass */
       break;
 
    case PIPE_FUNC_NOTEQUAL:
@@ -1207,7 +1207,6 @@ gen_stencil_test(struct spe_function *f, const struct pipe_stencil_state *state,
    case PIPE_FUNC_NEVER:
       /* stencil_pass = mask & 0 = 0 */
       spe_load_uint(f, stencil_pass_reg, 0);
-      spe_move(f, stencil_pass_reg, mask_reg);  /* zmask = mask */
       break;
 
    case PIPE_FUNC_ALWAYS:
@@ -1483,6 +1482,10 @@ gen_get_stencil_values(struct spe_function *f, const struct pipe_depth_stencil_a
    } /* End of calculations for back-facing stencil */
 }
 
+/* Note that fbZ_reg may *not* be set on entry, if in fact
+ * the depth test is not enabled.  This function must not use
+ * the register if depth is not enabled.
+ */
 static boolean
 gen_stencil_depth_test(struct spe_function *f, 
                        const struct pipe_depth_stencil_alpha_state *dsa, 
@@ -1522,6 +1525,7 @@ gen_stencil_depth_test(struct spe_function *f,
     * have to spend the complexity to track the more difficult variant
     * register usage scenarios.
     */
+   spe_comment(f, 0, "Allocating stencil register set");
    spe_allocate_register_set(f);
 
    /* Calculate the writemask.  If the writemask is trivial (either
@@ -1538,7 +1542,7 @@ gen_stencil_depth_test(struct spe_function *f,
       need_to_calculate_stencil_values = false;
       need_to_writemask_stencil_values = false;
    }
-   else if (dsa->stencil[0].write_mask == 0xff && (!dsa->stencil[1].enabled || dsa->stencil[1].write_mask == 0x00)) {
+   else if (dsa->stencil[0].write_mask == 0xff && (!dsa->stencil[1].enabled || dsa->stencil[1].write_mask == 0xff)) {
       /* Still trivial, but a little less so.  We need to write the stencil
        * values, but we don't need to mask them.
        */
@@ -1556,10 +1560,12 @@ gen_stencil_depth_test(struct spe_function *f,
        * writemask, we'll have to generate code that merges the
        * two masks into a single effective mask based on fragment facing.
        */
+      spe_comment(f, 0, "Computing stencil writemask");
       stencil_writemask_reg = spe_allocate_available_register(f);
       spe_load_uint(f, stencil_writemask_reg, dsa->stencil[0].write_mask);
       if (dsa->stencil[1].enabled && dsa->stencil[0].write_mask != dsa->stencil[1].write_mask) {
          unsigned int back_write_mask_reg = spe_allocate_available_register(f);
+         spe_comment(f, 0, "Resolving two-sided stencil writemask");
          spe_load_uint(f, back_write_mask_reg, dsa->stencil[1].write_mask);
          spe_selb(f, stencil_writemask_reg, stencil_writemask_reg, back_write_mask_reg, facing_reg);
          spe_release_register(f, back_write_mask_reg);
@@ -1575,6 +1581,7 @@ gen_stencil_depth_test(struct spe_function *f,
     * This test will *not* change the value in mask_reg (because we don't
     * yet know whether to apply the two-sided stencil or one-sided stencil).
     */
+   spe_comment(f, 0, "Running basic stencil test");
    stencil_pass_reg = spe_allocate_available_register(f);
    gen_stencil_test(f, &dsa->stencil[0], mask_reg, fbS_reg, stencil_pass_reg);
 
@@ -1584,6 +1591,7 @@ gen_stencil_depth_test(struct spe_function *f,
     */
    if (dsa->stencil[1].enabled) {
       unsigned int temp_reg = spe_allocate_available_register(f);
+      spe_comment(f, 0, "Running backface stencil test");
       gen_stencil_test(f, &dsa->stencil[1], mask_reg, fbS_reg, temp_reg);
       spe_selb(f, stencil_pass_reg, stencil_pass_reg, temp_reg, facing_reg);
       spe_release_register(f, temp_reg);
@@ -1597,6 +1605,7 @@ gen_stencil_depth_test(struct spe_function *f,
     * stencil test, and because the depth test will update the 
     * mask of valid fragments based on the results of the depth test).
     */
+   spe_comment(f, 0, "Computing stencil fail mask and updating fragment mask");
    stencil_fail_reg = spe_allocate_available_register(f);
    spe_andc(f, stencil_fail_reg, mask_reg, stencil_pass_reg);
    /* Now remove the stenciled-out pixels from the valid fragment mask,
@@ -1623,6 +1632,7 @@ gen_stencil_depth_test(struct spe_function *f,
        * This function will allocate a variant number of registers that
        * will be released as part of the register set.
        */
+      spe_comment(f, 0, "Computing stencil values");
       gen_get_stencil_values(f, dsa, fbS_reg, 
          &front_stencil_fail_values, &front_stencil_pass_depth_fail_values, 
          &front_stencil_pass_depth_pass_values, &back_stencil_fail_values, 
@@ -1652,6 +1662,7 @@ gen_stencil_depth_test(struct spe_function *f,
          stencil_pass_depth_pass_values = front_stencil_pass_depth_pass_values;
       }
       else { /* two-sided stencil enabled */
+         spe_comment(f, 0, "Resolving backface stencil values");
          /* Allocate new registers for the needed merged values */
          stencil_fail_values = spe_allocate_available_register(f);
          spe_selb(f, stencil_fail_values, front_stencil_fail_values, back_stencil_fail_values, facing_reg);
@@ -1678,11 +1689,13 @@ gen_stencil_depth_test(struct spe_function *f,
     * on the results of the test.
     */
    if (dsa->depth.enabled) {
+      spe_comment(f, 0, "Running stencil depth test");
       zmask_reg = spe_allocate_available_register(f);
       modified_buffers |= gen_depth_test(f, dsa, mask_reg, fragZ_reg, fbZ_reg, zmask_reg);
    }
 
    if (need_to_calculate_stencil_values) {
+
       /* If we need to writemask the stencil values before going into
        * the stencil buffer, we'll have to use a new register to
        * hold the new values.  If not, we can just keep using the
@@ -1690,8 +1703,8 @@ gen_stencil_depth_test(struct spe_function *f,
        */
       if (need_to_writemask_stencil_values) {
          newS_reg = spe_allocate_available_register(f);
+         spe_comment(f, 0, "Saving current stencil values for writemasking");
          spe_move(f, newS_reg, fbS_reg);
-         modified_buffers = true;
       }
       else {
          newS_reg = fbS_reg;
@@ -1699,7 +1712,9 @@ gen_stencil_depth_test(struct spe_function *f,
 
       /* Merge in the selected stencil fail values */
       if (stencil_fail_values != fbS_reg) {
+         spe_comment(f, 0, "Loading stencil fail values");
          spe_selb(f, newS_reg, newS_reg, stencil_fail_values, stencil_fail_reg);
+         modified_buffers = true;
       }
 
       /* Same for the stencil pass/depth fail values.  If this calculation
@@ -1714,20 +1729,36 @@ gen_stencil_depth_test(struct spe_function *f,
           * set above if we're here.
           */
          unsigned int stencil_pass_depth_fail_mask = spe_allocate_available_register(f);
+         spe_comment(f, 0, "Loading stencil pass/depth fail values");
          spe_andc(f, stencil_pass_depth_fail_mask, stencil_pass_reg, zmask_reg);
 
          spe_selb(f, newS_reg, newS_reg, stencil_pass_depth_fail_values, stencil_pass_depth_fail_mask);
 
          spe_release_register(f, stencil_pass_depth_fail_mask);
+         modified_buffers = true;
       }
 
-      /* Same for the stencil pass/depth pass mask */
+      /* Same for the stencil pass/depth pass mask.  Note that we
+       * *can* get here with zmask_reg being unset (if the depth
+       * test is off but the stencil test is on).  In this case,
+       * we assume the depth test passes, and don't need to mask
+       * the stencil pass mask with the Z mask.
+       */
       if (stencil_pass_depth_pass_values != fbS_reg) {
-         unsigned int stencil_pass_depth_pass_mask = spe_allocate_available_register(f);
-         spe_and(f, stencil_pass_depth_pass_mask, stencil_pass_reg, zmask_reg);
-
-         spe_selb(f, newS_reg, newS_reg, stencil_pass_depth_pass_values, stencil_pass_depth_pass_mask);
-         spe_release_register(f, stencil_pass_depth_pass_mask);
+         if (dsa->depth.enabled) {
+            unsigned int stencil_pass_depth_pass_mask = spe_allocate_available_register(f);
+            /* We'll need a separate register */
+            spe_comment(f, 0, "Loading stencil pass/depth pass values");
+            spe_and(f, stencil_pass_depth_pass_mask, stencil_pass_reg, zmask_reg);
+            spe_selb(f, newS_reg, newS_reg, stencil_pass_depth_pass_values, stencil_pass_depth_pass_mask);
+            spe_release_register(f, stencil_pass_depth_pass_mask);
+         }
+         else {
+            /* We can use the same stencil-pass register */
+            spe_comment(f, 0, "Loading stencil pass values");
+            spe_selb(f, newS_reg, newS_reg, stencil_pass_depth_pass_values, stencil_pass_reg);
+         }
+         modified_buffers = true;
       }
 
       /* Almost done.  If we need to writemask, do it now, leaving the
@@ -1736,14 +1767,16 @@ gen_stencil_depth_test(struct spe_function *f,
        * so there's nothing more to do.
        */
 
-      if (need_to_writemask_stencil_values) {
+      if (need_to_writemask_stencil_values && modified_buffers) {
          /* The Select Bytes command makes a fine writemask.  Where
           * the mask is 0, the first (original) values are retained,
           * effectively masking out changes.  Where the mask is 1, the
           * second (new) values are retained, incorporating changes.
           */
+         spe_comment(f, 0, "Writemasking new stencil values");
          spe_selb(f, fbS_reg, fbS_reg, newS_reg, stencil_writemask_reg);
       }
+
    } /* done calculating stencil values */
 
    /* The stencil and/or depth values have been applied, and the
@@ -1752,6 +1785,7 @@ gen_stencil_depth_test(struct spe_function *f,
     * of registers that we didn't bother tracking.  Release all
     * those registers as part of the register set, and go home.
     */
+   spe_comment(f, 0, "Releasing stencil register set");
    spe_release_register_set(f);
 
    /* Return true if we could have modified the stencil and/or
@@ -1869,7 +1903,7 @@ cell_gen_fragment_function(struct cell_context *cell, struct spe_function *f)
       boolean fbS_reg_set = false, fbZ_reg_set = false;
       unsigned int fbS_reg, fbZ_reg = 0;
 
-      spe_comment(f, 0, "Fetch quad's Z/stencil values from tile");
+      spe_comment(f, 0, "Fetching Z/stencil quad from tile");
 
       /* fetch quad of depth/stencil values from tile at (x,y) */
       /* Load: fbZS_reg = memory[depth_tile_reg + offset_reg] */
@@ -1973,13 +2007,18 @@ cell_gen_fragment_function(struct cell_context *cell, struct spe_function *f)
           * tests.
           */
          ASSERT(fbS_reg_set);
-         ASSERT(fbZ_reg_set);
          spe_comment(f, 0, "Perform stencil test");
 
+         /* Note that fbZ_reg may not be set on entry, if stenciling
+          * is enabled but there's no Z-buffer.  The 
+          * gen_stencil_depth_test() function must ignore the
+          * fbZ_reg register if depth is not enabled.
+          */
          write_depth_stencil = gen_stencil_depth_test(f, dsa, facing_reg, mask_reg, fragZ_reg, fbZ_reg, fbS_reg);
       }
       else if (dsa->depth.enabled) {
          int zmask_reg = spe_allocate_available_register(f);
+         ASSERT(fbZ_reg_set);
          spe_comment(f, 0, "Perform depth test");
          write_depth_stencil = gen_depth_test(f, dsa, mask_reg, fragZ_reg, fbZ_reg, zmask_reg);
          spe_release_register(f, zmask_reg);
@@ -1996,26 +2035,39 @@ cell_gen_fragment_function(struct cell_context *cell, struct spe_function *f)
          spe_comment(f, 0, "Store quad's depth/stencil values in tile");
          if (zs_format == PIPE_FORMAT_S8Z24_UNORM ||
              zs_format == PIPE_FORMAT_X8Z24_UNORM) {
-            if (fbS_reg_set) {
+            if (fbS_reg_set && fbZ_reg_set) {
                spe_shli(f, fbS_reg, fbS_reg, 24); /* fbS = fbS << 24 */
                spe_or(f, fbZS_reg, fbS_reg, fbZ_reg); /* fbZS = fbS | fbZ */
             }
+            else if (fbS_reg_set) {
+               spe_shli(f, fbZS_reg, fbS_reg, 24); /* fbS = fbS << 24 */
+            }
             else {
                spe_move(f, fbZS_reg, fbZ_reg);
             }
          }
          else if (zs_format == PIPE_FORMAT_Z24S8_UNORM ||
                   zs_format == PIPE_FORMAT_Z24X8_UNORM) {
-            spe_shli(f, fbZ_reg, fbZ_reg, 8); /* fbZ = fbZ << 8 */
-            if (fbS_reg_set) {
+            if (fbS_reg_set && fbZ_reg_set) {
+               spe_shli(f, fbZ_reg, fbZ_reg, 8); /* fbZ = fbZ << 8 */
                spe_or(f, fbZS_reg, fbS_reg, fbZ_reg); /* fbZS = fbS | fbZ */
             }
+            else if (fbS_reg_set) {
+               spe_move(f, fbZS_reg, fbS_reg);
+            }
+            else {
+               spe_shli(f, fbZ_reg, fbZ_reg, 8); /* fbZ = fbZ << 8 */
+            }
          }
          else if (zs_format == PIPE_FORMAT_Z32_UNORM) {
-            spe_move(f, fbZS_reg, fbZ_reg); /* fbZS = fbZ */
+            if (fbZ_reg_set) {
+               spe_move(f, fbZS_reg, fbZ_reg); /* fbZS = fbZ */
+            }
          }
          else if (zs_format == PIPE_FORMAT_Z16_UNORM) {
-            spe_move(f, fbZS_reg, fbZ_reg); /* fbZS = fbZ */
+            if (fbZ_reg_set) {
+               spe_move(f, fbZS_reg, fbZ_reg); /* fbZS = fbZ */
+            }
          }
          else if (zs_format == PIPE_FORMAT_S8_UNORM) {
             ASSERT(0);   /* XXX to do */