[Mesa-dev] [PATCH RFC 10/11] glsl: add a pass to convert out of SSA form
Connor Abbott
cwabbott0 at gmail.com
Wed Jan 22 09:16:57 PST 2014
Right now we are being basically as naive as possible, and inserting
more copies than necessary. It is possible to implement a more
sophisticated algorithm later, although extending the current copy
propagation pass to support loops better and/or relying on backends to
do copy propagation may make this unecessary.
---
src/glsl/Makefile.sources | 1 +
src/glsl/ir_optimization.h | 1 +
src/glsl/opt_from_ssa.cpp | 198 +++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 200 insertions(+)
create mode 100644 src/glsl/opt_from_ssa.cpp
diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index 961784b..55859ed 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -94,6 +94,7 @@ LIBGLSL_FILES = \
$(GLSL_SRCDIR)/opt_dead_functions.cpp \
$(GLSL_SRCDIR)/opt_flatten_nested_if_blocks.cpp \
$(GLSL_SRCDIR)/opt_flip_matrices.cpp \
+ $(GLSL_SRCDIR)/opt_from_ssa.cpp \
$(GLSL_SRCDIR)/opt_function_inlining.cpp \
$(GLSL_SRCDIR)/opt_if_simplification.cpp \
$(GLSL_SRCDIR)/opt_noop_swizzle.cpp \
diff --git a/src/glsl/ir_optimization.h b/src/glsl/ir_optimization.h
index 92c8b57..9c0ff31 100644
--- a/src/glsl/ir_optimization.h
+++ b/src/glsl/ir_optimization.h
@@ -66,6 +66,7 @@ enum lower_packing_builtins_op {
};
void convert_to_ssa(exec_list *instructions);
+void convert_from_ssa(exec_list *instructions);
bool do_common_optimization(exec_list *ir, bool linked,
bool uniform_locations_assigned,
diff --git a/src/glsl/opt_from_ssa.cpp b/src/glsl/opt_from_ssa.cpp
new file mode 100644
index 0000000..6071c45
--- /dev/null
+++ b/src/glsl/opt_from_ssa.cpp
@@ -0,0 +1,198 @@
+/*
+ * Copyright © 2013 Connor Abbott (connor at abbott.cx)
+ *
+ * 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 "ir.h"
+#include "ir_builder.h"
+
+/**
+ * \file opt_from_ssa.cpp
+ *
+ * This file removes all the SSA temporaries and phi nodes from a program. It
+ * immplements Method I of the paper "Translating out of Single Static
+ * Assignment Form" by Sreedhar et. al., a naive method that inserts many more
+ * copies than necessary; it is assumed that later copy propagation passes will
+ * clean up the result of this pass.
+ */
+
+using namespace ir_builder;
+
+static ir_variable *
+insert_decl(exec_list *instrs, const glsl_type *type, void *mem_ctx)
+{
+ ir_variable *var = new(mem_ctx) ir_variable(type, "phi_temp",
+ ir_var_temporary);
+ instrs->push_head(var);
+ return var;
+}
+
+static void
+eliminate_phi_if(ir_phi_if *phi, ir_if *ir, exec_list *instrs)
+{
+ ir_variable *var = insert_decl(instrs, phi->dest->type, ralloc_parent(ir));
+
+ /*
+ * This converts the destination of the phi node into a non-SSA variable,
+ * which ir_from_ssa_visitor::visit(ir_dereference_variable *) would normally
+ * do. We need to do this here because otherwise, the assignment we're
+ * inserting here will get skipped by the list visitor macro and it won't
+ * get converted.
+ */
+
+ ir->insert_after(phi->dest);
+ phi->dest->insert_after(assign(phi->dest, var));
+ phi->dest->data.mode = ir_var_temporary;
+
+ if (phi->if_src != NULL)
+ ir->then_instructions.push_tail(assign(var, phi->if_src));
+
+ if (phi->else_src != NULL)
+ ir->else_instructions.push_tail(assign(var, phi->else_src));
+
+ phi->remove();
+}
+
+static void
+eliminate_phi_loop_begin(ir_phi_loop_begin *phi, ir_loop *ir, exec_list *instrs)
+{
+ ir_variable *var = insert_decl(instrs, phi->dest->type, ralloc_parent(ir));
+ ir->body_instructions.push_head(phi->dest);
+ phi->dest->insert_after(assign(phi->dest, var));
+ phi->dest->data.mode = ir_var_temporary;
+
+ if (phi->enter_src != NULL)
+ ir->insert_before(assign(var, phi->enter_src));
+
+ if (phi->repeat_src != NULL)
+ ir->body_instructions.push_tail(assign(var, phi->repeat_src));
+
+ foreach_list(n, &phi->continue_srcs) {
+ ir_phi_jump_src *src = (ir_phi_jump_src *) n;
+
+ if (src->src != NULL)
+ src->jump->insert_before(assign(var, src->src));
+ }
+
+ phi->remove();
+}
+
+static void
+eliminate_phi_loop_end(ir_phi_loop_end *phi, ir_loop *ir, exec_list *instrs)
+{
+ ir_variable *var = insert_decl(instrs, phi->dest->type, ralloc_parent(ir));
+ ir->insert_after(phi->dest);
+ phi->dest->insert_after(assign(phi->dest, var));
+ phi->dest->data.mode = ir_var_temporary;
+
+ foreach_list(n, &phi->break_srcs) {
+ ir_phi_jump_src *src = (ir_phi_jump_src *) n;
+
+ if (src->src != NULL)
+ src->jump->insert_before(assign(var, src->src));
+ }
+
+ phi->remove();
+}
+
+namespace {
+
+class ir_from_ssa_visitor : public ir_hierarchical_visitor
+{
+public:
+ ir_from_ssa_visitor(exec_list *base_instrs) : base_instrs(base_instrs)
+ {
+ }
+
+ virtual ir_visitor_status visit_leave(ir_if *);
+ virtual ir_visitor_status visit_enter(ir_loop *);
+ virtual ir_visitor_status visit_leave(ir_loop *);
+ virtual ir_visitor_status visit(ir_dereference_variable *);
+
+private:
+ exec_list *base_instrs;
+};
+
+};
+
+ir_visitor_status
+ir_from_ssa_visitor::visit_leave(ir_if *ir)
+{
+ foreach_list_safe(n, &ir->phi_nodes) {
+ eliminate_phi_if((ir_phi_if *) n, ir, this->base_instrs);
+ }
+
+ return visit_continue;
+}
+
+ir_visitor_status
+ir_from_ssa_visitor::visit_enter(ir_loop *ir)
+{
+ foreach_list_safe(n, &ir->begin_phi_nodes) {
+ eliminate_phi_loop_begin((ir_phi_loop_begin *) n, ir, this->base_instrs);
+ }
+
+ return visit_continue;
+}
+
+ir_visitor_status
+ir_from_ssa_visitor::visit_leave(ir_loop *ir)
+{
+ foreach_list_safe(n, &ir->end_phi_nodes) {
+ eliminate_phi_loop_end((ir_phi_loop_end *) n, ir, this->base_instrs);
+ }
+
+ return visit_continue;
+}
+
+ir_visitor_status
+ir_from_ssa_visitor::visit(ir_dereference_variable *ir)
+{
+ if (this->in_assignee && ir->var->data.mode == ir_var_temporary_ssa) {
+ this->base_ir->insert_before(ir->var);
+ ir->var->data.mode = ir_var_temporary;
+ }
+
+ return visit_continue;
+}
+
+static void
+convert_from_ssa_function(exec_list *instructions)
+{
+ ir_from_ssa_visitor v(instructions);
+ v.run(instructions);
+}
+
+void
+convert_from_ssa(exec_list *instructions)
+{
+ foreach_list(node, instructions) {
+ ir_instruction *ir = (ir_instruction *) node;
+ ir_function *f = ir->as_function();
+ if (f) {
+ foreach_list(sig_node, &f->signatures) {
+ ir_function_signature *sig = (ir_function_signature *) sig_node;
+
+ convert_from_ssa_function(&sig->body);
+ }
+ }
+ }
+}
--
1.8.3.1
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