[Mesa-dev] [PATCH 019/133] nir: add an SSA-based dead code elimination pass
Jason Ekstrand
jason at jlekstrand.net
Mon Dec 15 22:04:29 PST 2014
From: Connor Abbott <connor.abbott at intel.com>
v2: Jason Ekstrand <jason.ekstrand at intel.com>:
whitespace fixes
---
src/glsl/Makefile.sources | 1 +
src/glsl/nir/nir.h | 6 ++
src/glsl/nir/nir_opt_dce.c | 184 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 191 insertions(+)
create mode 100644 src/glsl/nir/nir_opt_dce.c
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index 556648b..eb390fb 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -26,6 +26,7 @@ NIR_FILES = \
$(GLSL_SRCDIR)/nir/nir_opcodes.c \
$(GLSL_SRCDIR)/nir/nir_opcodes.h \
$(GLSL_SRCDIR)/nir/nir_opt_copy_propagate.c \
+ $(GLSL_SRCDIR)/nir/nir_opt_dce.c \
$(GLSL_SRCDIR)/nir/nir_opt_global_to_local.c \
$(GLSL_SRCDIR)/nir/nir_print.c \
$(GLSL_SRCDIR)/nir/nir_remove_dead_variables.c \
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index a5cb5ed..c5500f7 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -397,6 +397,9 @@ typedef struct {
struct exec_node node;
nir_instr_type type;
struct nir_block *block;
+
+ /* flag for dead code elimination (see nir_opt_dce.c) */
+ bool live;
} nir_instr;
#define nir_instr_next(instr) \
@@ -1296,6 +1299,9 @@ bool nir_opt_global_to_local(nir_shader *shader);
bool nir_copy_prop_impl(nir_function_impl *impl);
bool nir_copy_prop(nir_shader *shader);
+bool nir_opt_dce_impl(nir_function_impl *impl);
+bool nir_opt_dce(nir_shader *shader);
+
#ifdef __cplusplus
} /* extern "C" */
#endif
diff --git a/src/glsl/nir/nir_opt_dce.c b/src/glsl/nir/nir_opt_dce.c
new file mode 100644
index 0000000..c18ba32
--- /dev/null
+++ b/src/glsl/nir/nir_opt_dce.c
@@ -0,0 +1,184 @@
+/*
+ * 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:
+ * Connor Abbott (cwabbott0 at gmail.com)
+ *
+ */
+
+#include "nir.h"
+
+/* SSA-based mark-and-sweep dead code elimination */
+
+typedef struct {
+ struct exec_node node;
+ nir_instr *instr;
+} worklist_elem;
+
+static void
+worklist_push(struct exec_list *worklist, nir_instr *instr)
+{
+ worklist_elem *elem = ralloc(worklist, worklist_elem);
+ elem->instr = instr;
+ instr->live = true;
+ exec_list_push_tail(worklist, &elem->node);
+}
+
+static nir_instr *
+worklist_pop(struct exec_list *worklist)
+{
+ struct exec_node *node = exec_list_pop_head(worklist);
+ worklist_elem *elem = exec_node_data(worklist_elem, node, node);
+ return elem->instr;
+}
+
+static bool
+mark_live_cb(nir_src *src, void *_state)
+{
+ struct exec_list *worklist = (struct exec_list *) _state;
+
+ if (src->is_ssa && !src->ssa->parent_instr->live) {
+ worklist_push(worklist, src->ssa->parent_instr);
+ }
+
+ return true;
+}
+
+static void
+init_instr(nir_instr *instr, struct exec_list *worklist)
+{
+ nir_alu_instr *alu_instr;
+ nir_intrinsic_instr *intrin_instr;
+ nir_tex_instr *tex_instr;
+ nir_load_const_instr *load_const_instr;
+
+ instr->live = false;
+
+ switch (instr->type) {
+ case nir_instr_type_call:
+ case nir_instr_type_jump:
+ worklist_push(worklist, instr);
+ break;
+
+ case nir_instr_type_alu:
+ alu_instr = nir_instr_as_alu(instr);
+ if (!alu_instr->dest.dest.is_ssa)
+ worklist_push(worklist, instr);
+ break;
+
+ case nir_instr_type_intrinsic:
+ intrin_instr = nir_instr_as_intrinsic(instr);
+ if (nir_intrinsic_infos[intrin_instr->intrinsic].flags &
+ NIR_INTRINSIC_CAN_ELIMINATE) {
+ if (nir_intrinsic_infos[intrin_instr->intrinsic].has_dest &&
+ !intrin_instr->dest.is_ssa) {
+ worklist_push(worklist, instr);
+ }
+ } else {
+ worklist_push(worklist, instr);
+ }
+ break;
+
+ case nir_instr_type_texture:
+ tex_instr = nir_instr_as_texture(instr);
+ if (!tex_instr->dest.is_ssa)
+ worklist_push(worklist, instr);
+ break;
+
+ case nir_instr_type_load_const:
+ load_const_instr = nir_instr_as_load_const(instr);
+ if (!load_const_instr->dest.is_ssa)
+ worklist_push(worklist, instr);
+ break;
+
+ default:
+ break;
+ }
+}
+
+static bool
+init_block_cb(nir_block *block, void *_state)
+{
+ struct exec_list *worklist = (struct exec_list *) _state;
+
+ nir_foreach_instr(block, instr)
+ init_instr(instr, worklist);
+
+ if (block->cf_node.node.next != NULL && /* check that we aren't the end node */
+ !nir_cf_node_is_last(&block->cf_node) &&
+ nir_cf_node_next(&block->cf_node)->type == nir_cf_node_if) {
+ nir_if *if_stmt = nir_cf_node_as_if(nir_cf_node_next(&block->cf_node));
+ if (if_stmt->condition.is_ssa &&
+ !if_stmt->condition.ssa->parent_instr->live)
+ worklist_push(worklist, if_stmt->condition.ssa->parent_instr);
+ }
+
+ return true;
+}
+
+static bool
+delete_block_cb(nir_block *block, void *_state)
+{
+ bool *progress = (bool *) _state;
+
+ nir_foreach_instr_safe(block, instr) {
+ if (!instr->live) {
+ nir_instr_remove(instr);
+ *progress = true;
+ }
+ }
+
+ return true;
+}
+
+bool
+nir_opt_dce_impl(nir_function_impl *impl)
+{
+ struct exec_list *worklist = ralloc(NULL, struct exec_list);
+ exec_list_make_empty(worklist);
+
+ nir_foreach_block(impl, init_block_cb, worklist);
+
+ while (!exec_list_is_empty(worklist)) {
+ nir_instr *instr = worklist_pop(worklist);
+ nir_foreach_src(instr, mark_live_cb, worklist);
+ }
+
+ ralloc_free(worklist);
+
+ bool progress = false;
+ nir_foreach_block(impl, delete_block_cb, &progress);
+
+ return progress;
+}
+
+bool
+nir_opt_dce(nir_shader *shader)
+{
+ bool progress = false;
+ nir_foreach_overload(shader, overload) {
+ if (overload->impl && nir_opt_dce_impl(overload->impl))
+ progress = true;
+ }
+
+ return progress;
+}
--
2.2.0
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