nir: Add pass to optimize intrinsics

Specifically, constant fold intrinsics from ARB_shader_group_vote, but I
suspect it'll be useful for other things in the future.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/compiler/Makefile.sources

@@ -254,6 +254,7 @@ NIR_FILES = \
 	nir/nir_opt_gcm.c \
 	nir/nir_opt_global_to_local.c \
 	nir/nir_opt_if.c \
+	nir/nir_opt_intrinsics.c \
 	nir/nir_opt_loop_unroll.c \
 	nir/nir_opt_move_comparisons.c \
 	nir/nir_opt_peephole_select.c \

src/compiler/nir/nir.h

@@ -2644,6 +2644,8 @@ bool nir_opt_gcm(nir_shader *shader, bool value_number);
 
 bool nir_opt_if(nir_shader *shader);
 
+bool nir_opt_intrinsics(nir_shader *shader);
+
 bool nir_opt_loop_unroll(nir_shader *shader, nir_variable_mode indirect_mask);
 
 bool nir_opt_move_comparisons(nir_shader *shader);

src/compiler/nir/nir_opt_intrinsics.c

@@ -0,0 +1,95 @@
+/*
+ * 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_opt_intrinsics.c
+ */
+
+static bool
+opt_intrinsics_impl(nir_function_impl *impl)
+{
+   nir_builder b;
+   nir_builder_init(&b, impl);
+   bool progress = false;
+
+   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);
+         nir_ssa_def *replacement = NULL;
+         b.cursor = nir_before_instr(instr);
+
+         switch (intrin->intrinsic) {
+         case nir_intrinsic_vote_any:
+         case nir_intrinsic_vote_all: {
+            nir_const_value *val = nir_src_as_const_value(intrin->src[0]);
+            if (!val)
+               continue;
+
+            replacement = nir_ssa_for_src(&b, intrin->src[0], 1);
+            break;
+         }
+         case nir_intrinsic_vote_eq: {
+            nir_const_value *val = nir_src_as_const_value(intrin->src[0]);
+            if (!val)
+               continue;
+
+            replacement = nir_imm_int(&b, NIR_TRUE);
+            break;
+         }
+         default:
+            break;
+         }
+
+         if (!replacement)
+            continue;
+
+         nir_ssa_def_rewrite_uses(&intrin->dest.ssa,
+                                  nir_src_for_ssa(replacement));
+         nir_instr_remove(instr);
+         nir_metadata_preserve(impl, nir_metadata_block_index |
+                                     nir_metadata_dominance);
+         progress = true;
+      }
+   }
+
+   return progress;
+}
+
+bool
+nir_opt_intrinsics(nir_shader *shader)
+{
+   bool progress = false;
+
+   nir_foreach_function(function, shader) {
+      if (function->impl)
+         progress |= opt_intrinsics_impl(function->impl);
+   }
+
+   return false;
+}

src/intel/compiler/brw_nir.c

@@ -553,6 +553,7 @@ nir_optimize(nir_shader *nir, const struct brw_compiler *compiler,
       OPT(nir_opt_dce);
       OPT(nir_opt_cse);
       OPT(nir_opt_peephole_select, 0);
+      OPT(nir_opt_intrinsics);
       OPT(nir_opt_algebraic);
       OPT(nir_opt_constant_folding);
       OPT(nir_opt_dead_cf);