nir: Add a passes for nir_intrinsic_convert_alu_types

This adds primarily two passes:  One is a lowering pass which turns
these conversion intrinsics into a series of ALU ops.  The other is an
optimization pass which attempt to simplify the conversion whenever
possible in the hopes that we can turn it into a "normal" conversion op
which doesn't need special treatment.

Reviewed-by: Jesse Natalie <jenatali@microsoft.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6945>

src/compiler/Makefile.sources

@@ -250,6 +250,7 @@ NIR_FILES = \
 	nir/nir_lower_clip_cull_distance_arrays.c \
 	nir/nir_lower_clip_disable.c \
 	nir/nir_lower_clip_halfz.c \
+	nir/nir_lower_convert_alu_types.c \
 	nir/nir_lower_variable_initializers.c \
 	nir/nir_lower_discard_to_demote.c \
 	nir/nir_lower_double_ops.c \

src/compiler/nir/meson.build

@@ -129,6 +129,7 @@ files_libnir = files(
   'nir_lower_clip_cull_distance_arrays.c',
   'nir_lower_clip_disable.c',
   'nir_lower_clip_halfz.c',
+  'nir_lower_convert_alu_types.c',
   'nir_lower_variable_initializers.c',
   'nir_lower_discard_to_demote.c',
   'nir_lower_double_ops.c',

src/compiler/nir/nir.h

@@ -4384,6 +4384,10 @@ bool nir_lower_alu_to_scalar(nir_shader *shader, nir_instr_filter_cb cb, const v
 bool nir_lower_bool_to_bitsize(nir_shader *shader);
 bool nir_lower_bool_to_float(nir_shader *shader);
 bool nir_lower_bool_to_int32(nir_shader *shader);
+bool nir_opt_simplify_convert_alu_types(nir_shader *shader);
+bool nir_lower_convert_alu_types(nir_shader *shader,
+                                 bool (*should_lower)(nir_intrinsic_instr *));
+bool nir_lower_constant_convert_alu_types(nir_shader *shader);
 bool nir_lower_int_to_float(nir_shader *shader);
 bool nir_lower_load_const_to_scalar(nir_shader *shader);
 bool nir_lower_read_invocation_to_scalar(nir_shader *shader);

src/compiler/nir/nir_lower_convert_alu_types.c

@@ -0,0 +1,182 @@
+/*
+ * Copyright © 2020 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"
+#include "nir_conversion_builder.h"
+
+static bool
+try_simplify_convert_intrin(nir_intrinsic_instr *conv)
+{
+   bool progress = false;
+
+   nir_alu_type src_type = nir_intrinsic_src_type(conv);
+   nir_alu_type dest_type = nir_intrinsic_dest_type(conv);
+
+   nir_rounding_mode rounding = nir_intrinsic_rounding_mode(conv);
+   nir_rounding_mode simple_rounding =
+      nir_simplify_conversion_rounding(src_type, dest_type, rounding);
+   if (rounding != simple_rounding) {
+      nir_intrinsic_set_rounding_mode(conv, simple_rounding);
+      progress = true;
+   }
+
+   if (nir_intrinsic_saturate(conv) &&
+       nir_alu_type_range_contains_type_range(dest_type, src_type)) {
+      nir_intrinsic_set_saturate(conv, false);
+      progress = true;
+   }
+
+   return progress;
+}
+
+static void
+lower_convert_alu_types_instr(nir_builder *b, nir_intrinsic_instr *conv)
+{
+   assert(conv->intrinsic == nir_intrinsic_convert_alu_types);
+         assert(conv->src[0].is_ssa && conv->dest.is_ssa);
+
+   b->cursor = nir_instr_remove(&conv->instr);
+   nir_ssa_def *val =
+      nir_convert_with_rounding(b, conv->src[0].ssa,
+                                nir_intrinsic_src_type(conv),
+                                nir_intrinsic_dest_type(conv),
+                                nir_intrinsic_rounding_mode(conv),
+                                nir_intrinsic_saturate(conv));
+   nir_ssa_def_rewrite_uses(&conv->dest.ssa, nir_src_for_ssa(val));
+}
+
+static bool
+opt_simplify_convert_alu_types_impl(nir_function_impl *impl)
+{
+   bool progress = false;
+   bool lowered_instr = 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 *conv = nir_instr_as_intrinsic(instr);
+         if (conv->intrinsic != nir_intrinsic_convert_alu_types)
+            continue;
+
+         if (try_simplify_convert_intrin(conv))
+            progress = true;
+
+         if (nir_intrinsic_rounding_mode(conv) == nir_rounding_mode_undef &&
+             !nir_intrinsic_saturate(conv)) {
+            lower_convert_alu_types_instr(&b, conv);
+            lowered_instr = true;
+         }
+      }
+   }
+
+   if (lowered_instr) {
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+   } else {
+      nir_metadata_preserve(impl, nir_metadata_all);
+   }
+
+   return progress;
+}
+
+bool
+nir_opt_simplify_convert_alu_types(nir_shader *shader)
+{
+   bool progress = false;
+
+   nir_foreach_function(func, shader) {
+      if (func->impl && opt_simplify_convert_alu_types_impl(func->impl))
+         progress = true;
+   }
+
+   return progress;
+}
+
+static bool
+lower_convert_alu_types_impl(nir_function_impl *impl,
+                             bool (*should_lower)(nir_intrinsic_instr *))
+{
+   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 *conv = nir_instr_as_intrinsic(instr);
+         if (conv->intrinsic != nir_intrinsic_convert_alu_types)
+            continue;
+
+         if (should_lower != NULL && !should_lower(conv))
+            continue;
+
+         lower_convert_alu_types_instr(&b, conv);
+         progress = true;
+      }
+   }
+
+   if (progress) {
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+   } else {
+      nir_metadata_preserve(impl, nir_metadata_all);
+   }
+
+   return progress;
+}
+
+bool
+nir_lower_convert_alu_types(nir_shader *shader,
+                            bool (*should_lower)(nir_intrinsic_instr *))
+{
+   bool progress = false;
+
+   nir_foreach_function(func, shader) {
+      if (func->impl && lower_convert_alu_types_impl(func->impl, should_lower))
+         progress = true;
+   }
+
+   return progress;
+}
+
+static bool
+is_constant(nir_intrinsic_instr *conv)
+{
+   assert(conv->intrinsic == nir_intrinsic_convert_alu_types);
+   return nir_src_is_const(conv->src[0]);
+}
+
+bool
+nir_lower_constant_convert_alu_types(nir_shader *shader)
+{
+   return nir_lower_convert_alu_types(shader, is_constant);
+}