nir: Add a lowering pass for texture projectors.

Not much hardware wants them these days, and it might give us a chance to
do CSE or algebraic at the NIR level.

Reviewed-by: Jason Ekstrand <[email protected]>

2 files changed, 143 insertions, 0 deletions

diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 24deb82d2e7..6e2aa97d498 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1601,6 +1601,7 @@ void nir_lower_samplers(nir_shader *shader,
                         struct gl_program *prog);
 
 void nir_lower_system_values(nir_shader *shader);
+void nir_lower_tex_projector(nir_shader *shader);
 
 void nir_lower_atomics(nir_shader *shader);
 void nir_lower_to_source_mods(nir_shader *shader);
diff --git a/src/glsl/nir/nir_lower_tex_projector.c b/src/glsl/nir/nir_lower_tex_projector.c
new file mode 100644
index 00000000000..6327b23f6a5
--- /dev/null
+++ b/src/glsl/nir/nir_lower_tex_projector.c
@@ -0,0 +1,142 @@
+/*
+ * Copyright © 2015 Broadcom
+ *
+ * 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 (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 NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS 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.
+ */
+
+/*
+ * This lowering pass converts the coordinate division for texture projection
+ * to be done in ALU instructions instead of asking the texture operation to
+ * do so.
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+static nir_ssa_def *
+channel(nir_builder *b, nir_ssa_def *def, int c)
+{
+   return nir_swizzle(b, def, (unsigned[4]){c, c, c, c}, 1, false);
+}
+
+static bool
+nir_lower_tex_projector_block(nir_block *block, void *void_state)
+{
+   nir_builder *b = void_state;
+
+   nir_foreach_instr_safe(block, instr) {
+      if (instr->type != nir_instr_type_tex)
+         continue;
+
+      nir_tex_instr *tex = nir_instr_as_tex(instr);
+      nir_builder_insert_before_instr(b, &tex->instr);
+
+      /* Find the projector in the srcs list, if present. */
+      int proj_index;
+      for (proj_index = 0; proj_index < tex->num_srcs; proj_index++) {
+         if (tex->src[proj_index].src_type == nir_tex_src_projector)
+            break;
+      }
+      if (proj_index == tex->num_srcs)
+         continue;
+      nir_ssa_def *inv_proj =
+         nir_frcp(b, nir_ssa_for_src(b, tex->src[proj_index].src, 1));
+
+      /* Walk through the sources projecting the arguments. */
+      for (int i = 0; i < tex->num_srcs; i++) {
+         switch (tex->src[i].src_type) {
+         case nir_tex_src_coord:
+         case nir_tex_src_comparitor:
+            break;
+         default:
+            continue;
+         }
+         nir_ssa_def *unprojected =
+            nir_ssa_for_src(b, tex->src[i].src, nir_tex_instr_src_size(tex, i));
+         nir_ssa_def *projected = nir_fmul(b, unprojected, inv_proj);
+
+         /* Array indices don't get projected, so make an new vector with the
+          * coordinate's array index untouched.
+          */
+         if (tex->is_array && tex->src[i].src_type == nir_tex_src_coord) {
+            switch (tex->coord_components) {
+            case 4:
+               projected = nir_vec4(b,
+                                    channel(b, projected, 0),
+                                    channel(b, projected, 1),
+                                    channel(b, projected, 2),
+                                    channel(b, unprojected, 3));
+               break;
+            case 3:
+               projected = nir_vec3(b,
+                                    channel(b, projected, 0),
+                                    channel(b, projected, 1),
+                                    channel(b, unprojected, 2));
+               break;
+            case 2:
+               projected = nir_vec2(b,
+                                    channel(b, projected, 0),
+                                    channel(b, unprojected, 1));
+               break;
+            default:
+               unreachable("bad texture coord count for array");
+               break;
+            }
+         }
+
+         nir_instr_rewrite_src(&tex->instr,
+                               &tex->src[i].src,
+                               nir_src_for_ssa(projected));
+      }
+
+      /* Now move the later tex sources down the array so that the projector
+       * disappears.
+       */
+      nir_src dead = {.is_ssa = false, .ssa = NULL};
+      nir_instr_rewrite_src(&tex->instr, &tex->src[proj_index].src, dead);
+      memmove(&tex->src[proj_index],
+              &tex->src[proj_index + 1],
+              (tex->num_srcs - proj_index) * sizeof(*tex->src));
+      tex->num_srcs--;
+   }
+
+   return true;
+}
+
+static void
+nir_lower_tex_projector_impl(nir_function_impl *impl)
+{
+   nir_builder b;
+   nir_builder_init(&b, impl);
+
+   nir_foreach_block(impl, nir_lower_tex_projector_block, &b);
+
+   nir_metadata_preserve(impl, nir_metadata_block_index |
+                               nir_metadata_dominance);
+}
+
+void
+nir_lower_tex_projector(nir_shader *shader)
+{
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl)
+         nir_lower_tex_projector_impl(overload->impl);
+   }
+}