nir: Add pass to scalarize read_invocation/read_first_invocation

i965 will want these to be scalar operations.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/Makefile.sources

@@ -229,6 +229,7 @@ NIR_FILES = \
 	nir/nir_lower_passthrough_edgeflags.c \
 	nir/nir_lower_patch_vertices.c \
 	nir/nir_lower_phis_to_scalar.c \
+	nir/nir_lower_read_invocation_to_scalar.c \
 	nir/nir_lower_regs_to_ssa.c \
 	nir/nir_lower_returns.c \
 	nir/nir_lower_samplers.c \

src/compiler/nir/nir.h

@@ -2432,7 +2432,7 @@ bool nir_move_vec_src_uses_to_dest(nir_shader *shader);
 bool nir_lower_vec_to_movs(nir_shader *shader);
 bool nir_lower_alu_to_scalar(nir_shader *shader);
 bool nir_lower_load_const_to_scalar(nir_shader *shader);
-
+bool nir_lower_read_invocation_to_scalar(nir_shader *shader);
 bool nir_lower_phis_to_scalar(nir_shader *shader);
 void nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask);
 

src/compiler/nir/nir_lower_read_invocation_to_scalar.c

@@ -0,0 +1,112 @@
+/*
+ * Copyright © 2017 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"
+
+/** @file nir_lower_read_invocation_to_scalar.c
+ *
+ * Replaces nir_intrinsic_read_invocation/nir_intrinsic_read_first_invocation
+ * operations with num_components != 1 with individual per-channel operations.
+ */
+
+static void
+lower_read_invocation_to_scalar(nir_builder *b, nir_intrinsic_instr *intrin)
+{
+   b->cursor = nir_before_instr(&intrin->instr);
+
+   nir_ssa_def *value = nir_ssa_for_src(b, intrin->src[0], intrin->num_components);
+   nir_ssa_def *reads[4];
+
+   for (unsigned i = 0; i < intrin->num_components; i++) {
+      nir_intrinsic_instr *chan_intrin =
+         nir_intrinsic_instr_create(b->shader, intrin->intrinsic);
+      nir_ssa_dest_init(&chan_intrin->instr, &chan_intrin->dest,
+                        1, intrin->dest.ssa.bit_size, NULL);
+      chan_intrin->num_components = 1;
+
+      /* value */
+      chan_intrin->src[0] = nir_src_for_ssa(nir_channel(b, value, i));
+      /* invocation */
+      if (intrin->intrinsic == nir_intrinsic_read_invocation)
+         nir_src_copy(&chan_intrin->src[1], &intrin->src[1], chan_intrin);
+
+      nir_builder_instr_insert(b, &chan_intrin->instr);
+
+      reads[i] = &chan_intrin->dest.ssa;
+   }
+
+   nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
+                            nir_src_for_ssa(nir_vec(b, reads,
+                                                    intrin->num_components)));
+   nir_instr_remove(&intrin->instr);
+}
+
+static bool
+nir_lower_read_invocation_to_scalar_impl(nir_function_impl *impl)
+{
+   bool progress = false;
+   nir_builder b;
+   nir_builder_init(&b, impl);
+
+   nir_foreach_block(block, impl) {
+      nir_foreach_instr_safe(instr, block) {
+         if (instr->type != nir_instr_type_intrinsic)
+            continue;
+
+         nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+
+         if (intrin->num_components == 1)
+            continue;
+
+         switch (intrin->intrinsic) {
+         case nir_intrinsic_read_invocation:
+         case nir_intrinsic_read_first_invocation:
+            lower_read_invocation_to_scalar(&b, intrin);
+            progress = true;
+            break;
+         default:
+            break;
+         }
+      }
+   }
+
+   if (progress) {
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+   }
+   return progress;
+}
+
+bool
+nir_lower_read_invocation_to_scalar(nir_shader *shader)
+{
+   bool progress = false;
+
+   nir_foreach_function(function, shader) {
+      if (function->impl)
+         progress |= nir_lower_read_invocation_to_scalar_impl(function->impl);
+   }
+
+   return progress;
+}