nir: split nir_opt_shrink_stores from nir_opt_shrink_vectors

This patch moves the shrinking of store sources into
a separate pass.
The reasoning behind this is that this pass usually only
needs to be called once while nir_shrink_vectors might
better be called several times. This allows to move
the pass(es) out of the optimization loops.

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14480>

src/compiler/nir/meson.build

@@ -245,6 +245,7 @@ files_libnir = files(
   'nir_opt_ray_queries.c',
   'nir_opt_rematerialize_compares.c',
   'nir_opt_remove_phis.c',
+  'nir_opt_shrink_stores.c',
   'nir_opt_shrink_vectors.c',
   'nir_opt_sink.c',
   'nir_opt_trivial_continues.c',

src/compiler/nir/nir.h

@@ -5281,6 +5281,8 @@ bool nir_opt_remove_phis_block(nir_block *block);
 
 bool nir_opt_phi_precision(nir_shader *shader);
 
+bool nir_opt_shrink_stores(nir_shader *shader, bool shrink_image_store);
+
 bool nir_opt_shrink_vectors(nir_shader *shader, bool shrink_image_store);
 
 bool nir_opt_trivial_continues(nir_shader *shader);

src/compiler/nir/nir_opt_shrink_stores.c

@@ -0,0 +1,130 @@
+/*
+ * Copyright © 2020 Google LLC
+ *
+ * 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.
+ */
+
+/**
+ * @file
+ *
+ * Removes unused trailing components from store data.
+ *
+ */
+
+#include "nir.h"
+#include "nir_builder.h"
+
+static bool
+opt_shrink_vectors_image_store(nir_builder *b, nir_intrinsic_instr *instr)
+{
+   enum pipe_format format;
+   if (instr->intrinsic == nir_intrinsic_image_deref_store) {
+      nir_deref_instr *deref = nir_src_as_deref(instr->src[0]);
+      format = nir_deref_instr_get_variable(deref)->data.image.format;
+   } else {
+      format = nir_intrinsic_format(instr);
+   }
+   if (format == PIPE_FORMAT_NONE)
+      return false;
+
+   unsigned components = util_format_get_nr_components(format);
+   if (components >= instr->num_components)
+      return false;
+
+   nir_ssa_def *data = nir_channels(b, instr->src[3].ssa, BITSET_MASK(components));
+   nir_instr_rewrite_src(&instr->instr, &instr->src[3], nir_src_for_ssa(data));
+   instr->num_components = components;
+
+   return true;
+}
+
+static bool
+opt_shrink_store_instr(nir_builder *b, nir_intrinsic_instr *instr, bool shrink_image_store)
+{
+   b->cursor = nir_before_instr(&instr->instr);
+
+   switch (instr->intrinsic) {
+   case nir_intrinsic_store_output:
+   case nir_intrinsic_store_per_vertex_output:
+   case nir_intrinsic_store_ssbo:
+   case nir_intrinsic_store_shared:
+   case nir_intrinsic_store_global:
+   case nir_intrinsic_store_scratch:
+      break;
+   case nir_intrinsic_bindless_image_store:
+   case nir_intrinsic_image_deref_store:
+   case nir_intrinsic_image_store:
+      return shrink_image_store && opt_shrink_vectors_image_store(b, instr);
+   default:
+      return false;
+   }
+
+   /* Must be a vectorized intrinsic that we can resize. */
+   assert(instr->num_components != 0);
+
+   /* Trim the num_components stored according to the write mask. */
+   unsigned write_mask = nir_intrinsic_write_mask(instr);
+   unsigned last_bit = util_last_bit(write_mask);
+   if (last_bit < instr->num_components && instr->src[0].is_ssa) {
+      nir_ssa_def *def = nir_channels(b, instr->src[0].ssa,
+                                      BITSET_MASK(last_bit));
+      nir_instr_rewrite_src(&instr->instr,
+                            &instr->src[0],
+                            nir_src_for_ssa(def));
+      instr->num_components = last_bit;
+
+      return true;
+   }
+
+   return false;
+}
+
+bool
+nir_opt_shrink_stores(nir_shader *shader, bool shrink_image_store)
+{
+   bool progress = false;
+
+   nir_foreach_function(function, shader) {
+      if (!function->impl)
+         continue;
+
+      nir_builder b;
+      nir_builder_init(&b, function->impl);
+
+      nir_foreach_block(block, function->impl) {
+         nir_foreach_instr(instr, block) {
+            if (instr->type != nir_instr_type_intrinsic)
+               continue;
+            nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
+            progress |= opt_shrink_store_instr(&b, intrin, shrink_image_store);
+         }
+      }
+
+      if (progress) {
+         nir_metadata_preserve(function->impl,
+                               nir_metadata_block_index |
+                               nir_metadata_dominance);
+      } else {
+         nir_metadata_preserve(function->impl, nir_metadata_all);
+      }
+   }
+
+   return progress;
+}