nir: Add a cubemap normalizing pass

This commit adds a pass to L1-normalize cube-map coordinates.  Some hardware
such as i965 requires that largest cube-map coordinate is +-1.  We had a
pass to perform this normalization in GLSL IR but we need it in NIR for
cube maps on ARB programs to work correctly.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

v2 (Suggested by Eric):
 - Do a vector fabs and split into components later
 - Move to core NIR

Reviewed-by: Eric Anholt <eric@anholt.net>

src/glsl/Makefile.sources

@@ -43,6 +43,7 @@ NIR_FILES = \
 	nir/nir_lower_var_copies.c \
 	nir/nir_lower_vec_to_movs.c \
 	nir/nir_metadata.c \
+	nir/nir_normalize_cubemap_coords.c \
 	nir/nir_opt_constant_folding.c \
 	nir/nir_opt_copy_propagate.c \
 	nir/nir_opt_cse.c \

src/glsl/nir/nir.h

@@ -1616,6 +1616,8 @@ void nir_lower_tex_projector(nir_shader *shader);
 void nir_lower_atomics(nir_shader *shader);
 void nir_lower_to_source_mods(nir_shader *shader);
 
+void nir_normalize_cubemap_coords(nir_shader *shader);
+
 void nir_live_variables_impl(nir_function_impl *impl);
 bool nir_ssa_defs_interfere(nir_ssa_def *a, nir_ssa_def *b);
 

src/glsl/nir/nir_normalize_cubemap_coords.c

@@ -0,0 +1,110 @@
+/*
+ * Copyright © 2015 Intel Corporation
+ *
+ * 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.
+ *
+ * Authors:
+ *    Jason Ekstrand <jason@jlekstrand.net>
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+/**
+ * This file implements a NIR lowering pass to perform the normalization of
+ * the cubemap coordinates to have the largest magnitude component be -1.0
+ * or 1.0.  This is based on the old GLSL IR based pass by Eric.
+ */
+
+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
+normalize_cubemap_coords_block(nir_block *block, void *void_state)
+{
+   nir_builder *b = void_state;
+
+   nir_foreach_instr(block, instr) {
+      if (instr->type != nir_instr_type_tex)
+         continue;
+
+      nir_tex_instr *tex = nir_instr_as_tex(instr);
+      if (tex->sampler_dim != GLSL_SAMPLER_DIM_CUBE)
+         continue;
+
+      nir_builder_insert_before_instr(b, &tex->instr);
+
+      for (unsigned i = 0; i < tex->num_srcs; i++) {
+         if (tex->src[i].src_type != nir_tex_src_coord)
+            continue;
+
+         nir_ssa_def *orig_coord =
+            nir_ssa_for_src(b, tex->src[i].src, nir_tex_instr_src_size(tex, i));
+         assert(orig_coord->num_components >= 3);
+
+         nir_ssa_def *abs = nir_fabs(b, orig_coord);
+         nir_ssa_def *norm = nir_fmax(b, channel(b, abs, 0),
+                                         nir_fmax(b, channel(b, abs, 1),
+                                                     channel(b, abs, 2)));
+
+         nir_ssa_def *normalized = nir_fmul(b, orig_coord, nir_frcp(b, norm));
+
+         /* Array indices don't have to be normalized, so make a new vector
+          * with the coordinate's array index untouched.
+          */
+         if (tex->coord_components == 4) {
+            normalized = nir_vec4(b,
+                                  channel(b, normalized, 0),
+                                  channel(b, normalized, 1),
+                                  channel(b, normalized, 2),
+                                  channel(b, orig_coord, 3));
+         }
+
+         nir_instr_rewrite_src(&tex->instr,
+                               &tex->src[i].src,
+                               nir_src_for_ssa(normalized));
+      }
+   }
+
+   return true;
+}
+
+static void
+normalize_cubemap_coords_impl(nir_function_impl *impl)
+{
+   nir_builder b;
+   nir_builder_init(&b, impl);
+
+   nir_foreach_block(impl, normalize_cubemap_coords_block, &b);
+
+   nir_metadata_preserve(impl, nir_metadata_block_index |
+                               nir_metadata_dominance);
+}
+
+void
+nir_normalize_cubemap_coords(nir_shader *shader)
+{
+   nir_foreach_overload(shader, overload)
+      if (overload->impl)
+         normalize_cubemap_coords_impl(overload->impl);
+}