nir: add a pass for lowering (un)pack_double_2x32

v2: Undo unintended change to the signature of
    nir_normalize_cubemap_coords (Iago).

v3: Move to compiler/nir (Iago)

v4: Remove Authors from copyright header (Michael Schellenberger)

v5 (Sam):
- Use nir_channel() and nir_ssa_for_alu_src() helpers (Jason)
- Inline lower_double_pack_instr() code into lower_double_pack_block()
  (Jason).
- Initialize nir_builder at lower_double_pack_impl() (Jason).

Signed-off-by: Iago Toral Quiroga <itoral@igalia.com>
Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/Makefile.sources

@@ -187,6 +187,7 @@ NIR_FILES = \
 	nir/nir_lower_alu_to_scalar.c \
 	nir/nir_lower_atomics.c \
 	nir/nir_lower_clip.c \
+	nir/nir_lower_double_packing.c \
 	nir/nir_lower_global_vars_to_local.c \
 	nir/nir_lower_gs_intrinsics.c \
 	nir/nir_lower_load_const_to_scalar.c \

src/compiler/glsl/Makefile.sources

@@ -38,6 +38,7 @@ NIR_FILES = \
 	nir/nir_lower_alu_to_scalar.c \
 	nir/nir_lower_atomics.c \
 	nir/nir_lower_clip.c \
+	nir/nir_lower_double_packing.c \
 	nir/nir_lower_global_vars_to_local.c \
 	nir/nir_lower_gs_intrinsics.c \
 	nir/nir_lower_load_const_to_scalar.c \

src/compiler/nir/Makefile.sources

@@ -30,6 +30,7 @@ NIR_FILES = \
 	nir_lower_alu_to_scalar.c \
 	nir_lower_atomics.c \
 	nir_lower_clip.c \
+	nir_lower_double_packing.c \
 	nir_lower_global_vars_to_local.c \
 	nir_lower_gs_intrinsics.c \
 	nir_lower_load_const_to_scalar.c \

src/compiler/nir/nir.h

@@ -2279,6 +2279,8 @@ void nir_lower_to_source_mods(nir_shader *shader);
 
 bool nir_lower_gs_intrinsics(nir_shader *shader);
 
+void nir_lower_double_pack(nir_shader *shader);
+
 bool nir_normalize_cubemap_coords(nir_shader *shader);
 
 void nir_live_ssa_defs_impl(nir_function_impl *impl);

src/compiler/nir/nir_lower_double_packing.c

@@ -0,0 +1,95 @@
+/*
+ * 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.
+ *
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+/*
+ * lowers:
+ *
+ * packDouble2x32(foo) -> packDouble2x32Split(foo.x, foo.y)
+ * unpackDouble2x32(foo) -> vec2(unpackDouble2x32_x(foo), unpackDouble2x32_y(foo))
+ */
+
+static nir_ssa_def *
+lower_pack_double(nir_builder *b, nir_ssa_def *src)
+{
+   return nir_pack_double_2x32_split(b, nir_channel(b, src, 0),
+                                        nir_channel(b, src, 1));
+}
+
+static nir_ssa_def *
+lower_unpack_double(nir_builder *b, nir_ssa_def *src)
+{
+   return nir_vec2(b, nir_unpack_double_2x32_split_x(b, src),
+                      nir_unpack_double_2x32_split_y(b, src));
+}
+
+static bool
+lower_double_pack_block(nir_block *block, void *ctx)
+{
+   nir_builder *b = (nir_builder *) ctx;
+
+   nir_foreach_instr_safe(block, instr) {
+      if (instr->type != nir_instr_type_alu)
+         continue;
+
+      nir_alu_instr *alu_instr = (nir_alu_instr *) instr;
+
+      if (alu_instr->op != nir_op_pack_double_2x32 &&
+          alu_instr->op != nir_op_unpack_double_2x32)
+         continue;
+
+      b->cursor = nir_before_instr(&alu_instr->instr);
+
+      nir_ssa_def *src = nir_ssa_for_alu_src(b, alu_instr, 0);
+      nir_ssa_def *dest =
+         alu_instr->op == nir_op_pack_double_2x32 ?
+         lower_pack_double(b, src) :
+         lower_unpack_double(b, src);
+
+      nir_ssa_def_rewrite_uses(&alu_instr->dest.dest.ssa, nir_src_for_ssa(dest));
+      nir_instr_remove(&alu_instr->instr);
+   }
+
+   return true;
+}
+
+static void
+lower_double_pack_impl(nir_function_impl *impl)
+{
+   nir_builder b;
+   nir_builder_init(&b, impl);
+   nir_foreach_block(impl, lower_double_pack_block, &b);
+}
+
+void
+nir_lower_double_pack(nir_shader *shader)
+{
+   nir_foreach_function(shader, function) {
+      if (function->impl)
+         lower_double_pack_impl(function->impl);
+   }
+}
+