[Mesa-dev] [RFC 12/12] nir: Add a pass to inline functions

[Jason Ekstrand]

This commit adds a new NIR pass that lowers all function calls away by
inlining the functions.
---

There are still two things missing here:

 1) We really shouldn't do the inline recursively.  We should keep a
    hash-table of inlined versions or something.

 2) It doesn't properly handle things like samplers as parameters.  Since
    those can only be "in" parameters, I had thought about treating the
    variable as a "proxy" and going through and rewriting all of the derefs
    that use it.  We could do the same thing for regular parameters when a
    shadow isn't needed.

Still, I thought it was worth sending out because it does work for most
cases.

 src/glsl/Makefile.sources           |   1 +
 src/glsl/nir/nir.h                  |   3 +
 src/glsl/nir/nir_inline_functions.c | 138 ++++++++++++++++++++++++++++++++++++
 3 files changed, 142 insertions(+)
 create mode 100644 src/glsl/nir/nir_inline_functions.c

diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index fa3868c..c271afd 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -35,6 +35,7 @@ NIR_FILES = \
 	nir/nir_dominance.c \
 	nir/nir_from_ssa.c \
 	nir/nir_gs_count_vertices.c \
+	nir/nir_inline_functions.c \
 	nir/nir_intrinsics.c \
 	nir/nir_intrinsics.h \
 	nir/nir_instr_set.c \
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index 2e29617..437f63a 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1938,6 +1938,9 @@ bool nir_split_var_copies(nir_shader *shader);
 bool nir_lower_returns_impl(nir_function_impl *impl);
 bool nir_lower_returns(nir_shader *shader);
 
+bool nir_inline_functions_impl(nir_function_impl *impl);
+bool nir_inline_functions(nir_shader *shader);
+
 void nir_lower_var_copy_instr(nir_intrinsic_instr *copy, void *mem_ctx);
 void nir_lower_var_copies(nir_shader *shader);
 
diff --git a/src/glsl/nir/nir_inline_functions.c b/src/glsl/nir/nir_inline_functions.c
new file mode 100644
index 0000000..e7e17ca
--- /dev/null
+++ b/src/glsl/nir/nir_inline_functions.c
@@ -0,0 +1,138 @@
+/*
+ * Copyright © 2015 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_control_flow.h"
+
+struct inline_functions_state {
+   nir_function_impl *impl;
+   nir_builder builder;
+   bool progress;
+};
+
+static bool
+inline_functions_block(nir_block *block, void *void_state)
+{
+   struct inline_functions_state *state = void_state;
+
+   nir_builder *b = &state->builder;
+
+   /* This is tricky.  We're iterating over instructions in a block but, as
+    * we go, the block and its instruction list are being split into
+    * pieces.  However, this *should* be safe since foreach_safe always
+    * stashes the next thing in the iteration.  That next thing will
+    * properly get moved to the next block when it gets split, and we
+    * continue iterating there.
+    */
+   nir_foreach_instr_safe(block, instr) {
+      if (instr->type != nir_instr_type_call)
+         continue;
+
+      state->progress = true;
+
+      nir_call_instr *call = nir_instr_as_call(instr);
+      assert(call->callee->impl);
+
+      nir_function_impl *callee_copy =
+         nir_function_impl_clone(call->callee->impl);
+
+      exec_list_append(&state->impl->locals, &callee_copy->locals);
+      exec_list_append(&state->impl->registers, &callee_copy->registers);
+
+      b->cursor = nir_before_instr(&call->instr);
+
+      /* Add copies of all in parameters */
+      assert(call->num_params == callee_copy->num_params);
+      for (unsigned i = 0; i < callee_copy->num_params; i++) {
+         /* Only in or inout parameters */
+         if (call->callee->params[i].param_type == nir_parameter_out)
+            continue;
+
+         nir_copy_deref_var(b, nir_deref_var_create(b->shader,
+                                                    callee_copy->params[i]),
+                               call->params[i]);
+      }
+
+      /* Pluck the body out of the function and place it here */
+      nir_cf_list body;
+      nir_cf_list_extract(&body, &callee_copy->body);
+      nir_cf_reinsert(&body, b->cursor);
+
+      b->cursor = nir_before_instr(&call->instr);
+
+      /* Add copies of all out parameters and the return */
+      assert(call->num_params == callee_copy->num_params);
+      for (unsigned i = 0; i < callee_copy->num_params; i++) {
+         /* Only out or inout parameters */
+         if (call->callee->params[i].param_type == nir_parameter_in)
+            continue;
+
+         nir_copy_deref_var(b, call->params[i],
+                               nir_deref_var_create(b->shader,
+                                                    callee_copy->params[i]));
+      }
+      if (!glsl_type_is_void(call->callee->return_type)) {
+         nir_copy_deref_var(b, call->return_deref,
+                               nir_deref_var_create(b->shader,
+                                                    callee_copy->return_var));
+      }
+
+      nir_instr_remove(&call->instr);
+   }
+
+   return true;
+}
+
+bool
+nir_inline_functions_impl(nir_function_impl *impl)
+{
+   struct inline_functions_state state;
+
+   state.progress = false;
+   state.impl = impl;
+   nir_builder_init(&state.builder, impl);
+
+   nir_foreach_block(impl, inline_functions_block, &state);
+
+   /* SSA and register indices are completely messed up now */
+   nir_index_ssa_defs(impl);
+   nir_index_local_regs(impl);
+
+   nir_metadata_preserve(impl, nir_metadata_none);
+
+   return state.progress;
+}
+
+bool
+nir_inline_functions(nir_shader *shader)
+{
+   bool progress = false;
+
+   nir_foreach_function(shader, function) {
+      if (function->impl)
+         progress = nir_inline_functions_impl(function->impl) || progress;
+   }
+
+   return progress;
+}
-- 
2.5.0.400.gff86faf