nir: Add a pass for lowering copy instructions

Reviewed-by: Connor Abbott <[email protected]>

2 files changed, 226 insertions, 0 deletions

diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 12cac728cff..1faeb02156c 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1461,6 +1461,9 @@ void nir_dump_cfg(nir_shader *shader, FILE *fp);
 
 void nir_split_var_copies(nir_shader *shader);
 
+void nir_lower_var_copy_instr(nir_intrinsic_instr *copy, void *mem_ctx);
+void nir_lower_var_copies(nir_shader *shader);
+
 void nir_lower_global_vars_to_local(nir_shader *shader);
 
 void nir_lower_locals_to_regs(nir_shader *shader);
diff --git a/src/glsl/nir/nir_lower_var_copies.c b/src/glsl/nir/nir_lower_var_copies.c
new file mode 100644
index 00000000000..a9d1a47ea69
--- /dev/null
+++ b/src/glsl/nir/nir_lower_var_copies.c
@@ -0,0 +1,223 @@
+/*
+ * Copyright © 2014 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.
+ *
+ * Authors:
+ *    Jason Ekstrand ([email protected])
+ *
+ */
+
+#include "nir.h"
+#include "nir_types.h"
+
+/*
+ * Lowers all copy intrinsics to sequences of load/store intrinsics.
+ */
+
+/* Walks down the deref chain and returns the next deref in the chain whose
+ * child is a wildcard.  In other words, given the chain  a[1].foo[*].bar,
+ * this function will return the deref to foo.  Calling it a second time
+ * with the [*].bar, it will return NULL.
+ */
+static nir_deref *
+deref_next_wildcard_parent(nir_deref *deref)
+{
+   for (nir_deref *tail = deref; tail->child; tail = tail->child) {
+      if (tail->child->deref_type != nir_deref_type_array)
+         continue;
+
+      nir_deref_array *arr = nir_deref_as_array(tail->child);
+
+      if (arr->deref_array_type == nir_deref_array_type_wildcard)
+         return tail;
+   }
+
+   return NULL;
+}
+
+/* Returns the last deref in the chain.
+ */
+static nir_deref *
+get_deref_tail(nir_deref *deref)
+{
+   while (deref->child)
+      deref = deref->child;
+
+   return deref;
+}
+
+static int
+type_get_length(const struct glsl_type *type)
+{
+   switch (glsl_get_base_type(type)) {
+   case GLSL_TYPE_STRUCT:
+   case GLSL_TYPE_ARRAY:
+      return glsl_get_length(type);
+   case GLSL_TYPE_FLOAT:
+   case GLSL_TYPE_INT:
+   case GLSL_TYPE_UINT:
+   case GLSL_TYPE_BOOL:
+      if (glsl_type_is_matrix(type))
+         return glsl_get_matrix_columns(type);
+      else
+         return glsl_get_vector_elements(type);
+   default:
+      unreachable("Invalid deref base type");
+   }
+}
+
+/* This function recursively walks the given deref chain and replaces the
+ * given copy instruction with an equivalent sequence load/store
+ * operations.
+ *
+ * @copy_instr    The copy instruction to replace; new instructions will be
+ *                inserted before this one
+ *
+ * @dest_head     The head of the destination variable deref chain
+ *
+ * @src_head      The head of the source variable deref chain
+ *
+ * @dest_tail     The current tail of the destination variable deref chain;
+ *                this is used for recursion and external callers of this
+ *                function should call it with tail == head
+ *
+ * @src_tail      The current tail of the source variable deref chain;
+ *                this is used for recursion and external callers of this
+ *                function should call it with tail == head
+ *
+ * @state         The current variable lowering state
+ */
+static void
+emit_copy_load_store(nir_intrinsic_instr *copy_instr,
+                     nir_deref_var *dest_head, nir_deref_var *src_head,
+                     nir_deref *dest_tail, nir_deref *src_tail, void *mem_ctx)
+{
+   /* Find the next pair of wildcards */
+   nir_deref *src_arr_parent = deref_next_wildcard_parent(src_tail);
+   nir_deref *dest_arr_parent = deref_next_wildcard_parent(dest_tail);
+
+   if (src_arr_parent || dest_arr_parent) {
+      /* Wildcards had better come in matched pairs */
+      assert(dest_arr_parent && dest_arr_parent);
+
+      nir_deref_array *src_arr = nir_deref_as_array(src_arr_parent->child);
+      nir_deref_array *dest_arr = nir_deref_as_array(dest_arr_parent->child);
+
+      unsigned length = type_get_length(src_arr_parent->type);
+      /* The wildcards should represent the same number of elements */
+      assert(length == type_get_length(dest_arr_parent->type));
+      assert(length > 0);
+
+      /* Walk over all of the elements that this wildcard refers to and
+       * call emit_copy_load_store on each one of them */
+      src_arr->deref_array_type = nir_deref_array_type_direct;
+      dest_arr->deref_array_type = nir_deref_array_type_direct;
+      for (unsigned i = 0; i < length; i++) {
+         src_arr->base_offset = i;
+         dest_arr->base_offset = i;
+         emit_copy_load_store(copy_instr, dest_head, src_head,
+                              &dest_arr->deref, &src_arr->deref, mem_ctx);
+      }
+      src_arr->deref_array_type = nir_deref_array_type_wildcard;
+      dest_arr->deref_array_type = nir_deref_array_type_wildcard;
+   } else {
+      /* In this case, we have no wildcards anymore, so all we have to do
+       * is just emit the load and store operations. */
+      src_tail = get_deref_tail(src_tail);
+      dest_tail = get_deref_tail(dest_tail);
+
+      assert(src_tail->type == dest_tail->type);
+
+      unsigned num_components = glsl_get_vector_elements(src_tail->type);
+
+      nir_deref *src_deref = nir_copy_deref(mem_ctx, &src_head->deref);
+      nir_deref *dest_deref = nir_copy_deref(mem_ctx, &dest_head->deref);
+
+      nir_intrinsic_instr *load =
+         nir_intrinsic_instr_create(mem_ctx, nir_intrinsic_load_var);
+      load->num_components = num_components;
+      load->variables[0] = nir_deref_as_var(src_deref);
+      load->dest.is_ssa = true;
+      nir_ssa_def_init(&load->instr, &load->dest.ssa, num_components, NULL);
+
+      nir_instr_insert_before(&copy_instr->instr, &load->instr);
+
+      nir_intrinsic_instr *store =
+         nir_intrinsic_instr_create(mem_ctx, nir_intrinsic_store_var);
+      store->num_components = num_components;
+      store->variables[0] = nir_deref_as_var(dest_deref);
+      store->src[0].is_ssa = true;
+      store->src[0].ssa = &load->dest.ssa;
+
+      nir_instr_insert_before(&copy_instr->instr, &store->instr);
+   }
+}
+
+/* Lowers a copy instruction to a sequence of load/store instructions
+ *
+ * The new instructions are placed before the copy instruction in the IR.
+ */
+void
+nir_lower_var_copy_instr(nir_intrinsic_instr *copy, void *mem_ctx)
+{
+   assert(copy->intrinsic == nir_intrinsic_copy_var);
+   emit_copy_load_store(copy, copy->variables[0], copy->variables[1],
+                        &copy->variables[0]->deref,
+                        &copy->variables[1]->deref, mem_ctx);
+}
+
+static bool
+lower_var_copies_block(nir_block *block, void *mem_ctx)
+{
+   nir_foreach_instr_safe(block, instr) {
+      if (instr->type != nir_instr_type_intrinsic)
+         continue;
+
+      nir_intrinsic_instr *copy = nir_instr_as_intrinsic(instr);
+      if (copy->intrinsic != nir_intrinsic_copy_var)
+         continue;
+
+      nir_lower_var_copy_instr(copy, mem_ctx);
+
+      nir_instr_remove(&copy->instr);
+      ralloc_free(copy);
+   }
+
+   return true;
+}
+
+static void
+lower_var_copies_impl(nir_function_impl *impl)
+{
+   nir_foreach_block(impl, lower_var_copies_block, ralloc_parent(impl));
+}
+
+/* Lowers every copy_var instruction in the program to a sequence of
+ * load/store instructions.
+ */
+void
+nir_lower_var_copies(nir_shader *shader)
+{
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl)
+         lower_var_copies_impl(overload->impl);
+   }
+}