nir: add nir_lower_uniforms_to_ubo pass

This is a further lowering of default-block uniform loads that transforms
load_uniform intrinsics into load_ubo intrinsics. This simplifies the rest
of the backend.

v2: transform from load_uniform instead of straight from variables

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

src/compiler/Makefile.sources

@@ -238,6 +238,7 @@ NIR_FILES = \
 	nir/nir_lower_tex.c \
 	nir/nir_lower_to_source_mods.c \
 	nir/nir_lower_two_sided_color.c \
+	nir/nir_lower_uniforms_to_ubo.c \
 	nir/nir_lower_vars_to_ssa.c \
 	nir/nir_lower_var_copies.c \
 	nir/nir_lower_vec_to_movs.c \

src/compiler/nir/nir.h

@@ -2581,6 +2581,7 @@ void nir_lower_bitmap(nir_shader *shader, const nir_lower_bitmap_options *option
 bool nir_lower_atomics(nir_shader *shader,
                        const struct gl_shader_program *shader_program);
 bool nir_lower_atomics_to_ssbo(nir_shader *shader, unsigned ssbo_offset);
+bool nir_lower_uniforms_to_ubo(nir_shader *shader);
 bool nir_lower_to_source_mods(nir_shader *shader);
 
 bool nir_lower_gs_intrinsics(nir_shader *shader);

src/compiler/nir/nir_lower_uniforms_to_ubo.c

@@ -0,0 +1,97 @@
+/*
+ * Copyright 2017 Advanced Micro Devices, Inc.
+ *
+ * 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
+ * on the rights to use, copy, modify, merge, publish, distribute, sub
+ * license, 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 NON-INFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHOR(S) AND/OR THEIR SUPPLIERS 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.
+ */
+
+/*
+ * Remap load_uniform intrinsics to UBO accesses of UBO binding point 0. Both
+ * the base and the offset are interpreted as 16-byte units.
+ *
+ * Simultaneously, remap existing UBO accesses by increasing their binding
+ * point by 1.
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+static bool
+lower_instr(nir_intrinsic_instr *instr, nir_builder *b)
+{
+   b->cursor = nir_before_instr(&instr->instr);
+
+   if (instr->intrinsic == nir_intrinsic_load_ubo) {
+      nir_ssa_def *old_idx = nir_ssa_for_src(b, instr->src[0], 1);
+      nir_ssa_def *new_idx = nir_iadd(b, old_idx, nir_imm_int(b, 1));
+      nir_instr_rewrite_src(&instr->instr, &instr->src[0],
+                            nir_src_for_ssa(new_idx));
+      return true;
+   }
+
+   if (instr->intrinsic == nir_intrinsic_load_uniform) {
+      nir_ssa_def *ubo_idx = nir_imm_int(b, 0);
+      nir_ssa_def *ubo_offset =
+         nir_imul(b, nir_imm_int(b, 16),
+                  nir_iadd(b, nir_imm_int(b, nir_intrinsic_base(instr)),
+                           nir_ssa_for_src(b, instr->src[0], 1)));
+
+      nir_intrinsic_instr *load =
+         nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_ubo);
+      load->num_components = instr->num_components;
+      load->src[0] = nir_src_for_ssa(ubo_idx);
+      load->src[1] = nir_src_for_ssa(ubo_offset);
+      nir_ssa_dest_init(&load->instr, &load->dest,
+                        load->num_components, instr->dest.ssa.bit_size,
+                        instr->dest.ssa.name);
+      nir_builder_instr_insert(b, &load->instr);
+      nir_ssa_def_rewrite_uses(&instr->dest.ssa, nir_src_for_ssa(&load->dest.ssa));
+
+      nir_instr_remove(&instr->instr);
+      return true;
+   }
+
+   return false;
+}
+
+bool
+nir_lower_uniforms_to_ubo(nir_shader *shader)
+{
+   bool progress = false;
+
+   nir_foreach_function(function, shader) {
+      if (function->impl) {
+         nir_builder builder;
+         nir_builder_init(&builder, function->impl);
+         nir_foreach_block(block, function->impl) {
+            nir_foreach_instr_safe(instr, block) {
+               if (instr->type == nir_instr_type_intrinsic)
+                  progress |= lower_instr(nir_instr_as_intrinsic(instr),
+                                          &builder);
+            }
+         }
+
+         nir_metadata_preserve(function->impl, nir_metadata_block_index |
+                                               nir_metadata_dominance);
+      }
+   }
+
+   return progress;
+}
+