glsl/standalone: Optimize add-of-neg to subtract

This just makes the output of the standalone compiler a little more
compact.

v2: Fix indexing typo noticed by Iago.  Move the add_neg_to_sub_visitor
to it's own header file.  Add a unit test that exercises the visitor.
Both the neg_a_plus_b and neg_a_plus_neg_b tests reproduced the bug that
Iago discovered.

Signed-off-by: Ian Romanick <[email protected]>
Reviewed-by: Nicolai Hähnle <[email protected]>

4 files changed, 276 insertions, 0 deletions

diff --git a/src/compiler/Makefile.glsl.am b/src/compiler/Makefile.glsl.am
index 8bfb902f11b..3eac677de0d 100644
--- a/src/compiler/Makefile.glsl.am
+++ b/src/compiler/Makefile.glsl.am
@@ -72,6 +72,7 @@ glsl_tests_general_ir_test_SOURCES =			\
 	glsl/tests/builtin_variable_test.cpp		\
 	glsl/tests/invalidate_locations_test.cpp	\
 	glsl/tests/general_ir_test.cpp			\
+	glsl/tests/opt_add_neg_to_sub_test.cpp		\
 	glsl/tests/varyings_test.cpp
 glsl_tests_general_ir_test_CFLAGS =			\
 	$(PTHREAD_CFLAGS)
diff --git a/src/compiler/glsl/opt_add_neg_to_sub.h b/src/compiler/glsl/opt_add_neg_to_sub.h
new file mode 100644
index 00000000000..9f970710a57
--- /dev/null
+++ b/src/compiler/glsl/opt_add_neg_to_sub.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright © 2016 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.
+ */
+
+#ifndef OPT_ADD_NEG_TO_SUB_H
+#define OPT_ADD_NEG_TO_SUB_H
+
+#include "ir.h"
+#include "ir_hierarchical_visitor.h"
+
+class add_neg_to_sub_visitor : public ir_hierarchical_visitor {
+public:
+   add_neg_to_sub_visitor()
+   {
+      /* empty */
+   }
+
+   ir_visitor_status visit_leave(ir_expression *ir)
+   {
+      if (ir->operation != ir_binop_add)
+         return visit_continue;
+
+      for (unsigned i = 0; i < 2; i++) {
+         ir_expression *const op = ir->operands[i]->as_expression();
+
+         if (op != NULL && op->operation == ir_unop_neg) {
+            ir->operation = ir_binop_sub;
+
+            /* This ensures that -a + b becomes b - a. */
+            if (i == 0)
+               ir->operands[0] = ir->operands[1];
+
+            ir->operands[1] = op->operands[0];
+            break;
+         }
+      }
+
+      return visit_continue;
+   }
+};
+
+#endif /* OPT_ADD_NEG_TO_SUB_H */
diff --git a/src/compiler/glsl/standalone.cpp b/src/compiler/glsl/standalone.cpp
index f0964900938..efc6da9d004 100644
--- a/src/compiler/glsl/standalone.cpp
+++ b/src/compiler/glsl/standalone.cpp
@@ -37,6 +37,7 @@
 #include "standalone_scaffolding.h"
 #include "standalone.h"
 #include "util/string_to_uint_map.h"
+#include "opt_add_neg_to_sub.h"
 
 static const struct standalone_options *options;
 
@@ -441,6 +442,9 @@ standalone_compile_shader(const struct standalone_options *_options,
          if (!shader)
             continue;
 
+         add_neg_to_sub_visitor v;
+         visit_list_elements(&v, shader->ir);
+
          shader->Program = rzalloc(shader, gl_program);
          init_gl_program(shader->Program, shader->Stage);
       }
diff --git a/src/compiler/glsl/tests/opt_add_neg_to_sub_test.cpp b/src/compiler/glsl/tests/opt_add_neg_to_sub_test.cpp
new file mode 100644
index 00000000000..b82e47ffb23
--- /dev/null
+++ b/src/compiler/glsl/tests/opt_add_neg_to_sub_test.cpp
@@ -0,0 +1,210 @@
+/*
+ * Copyright © 2016 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 <gtest/gtest.h>
+#include "ir.h"
+#include "ir_builder.h"
+#include "opt_add_neg_to_sub.h"
+
+using namespace ir_builder;
+
+class add_neg_to_sub : public ::testing::Test {
+public:
+   virtual void SetUp();
+   virtual void TearDown();
+
+   exec_list instructions;
+   ir_factory *body;
+   void *mem_ctx;
+   ir_variable *var_a;
+   ir_variable *var_b;
+   ir_variable *var_c;
+   add_neg_to_sub_visitor v;
+};
+
+void
+add_neg_to_sub::SetUp()
+{
+   mem_ctx = ralloc_context(NULL);
+
+   instructions.make_empty();
+   body = new ir_factory(&instructions, mem_ctx);
+
+   var_a = new(mem_ctx) ir_variable(glsl_type::float_type,
+                                    "a",
+                                    ir_var_temporary);
+
+   var_b = new(mem_ctx) ir_variable(glsl_type::float_type,
+                                    "b",
+                                    ir_var_temporary);
+
+   var_c = new(mem_ctx) ir_variable(glsl_type::float_type,
+                                    "c",
+                                    ir_var_temporary);
+}
+
+void
+add_neg_to_sub::TearDown()
+{
+   delete body;
+   body = NULL;
+
+   ralloc_free(mem_ctx);
+   mem_ctx = NULL;
+}
+
+TEST_F(add_neg_to_sub, a_plus_b)
+{
+   body->emit(assign(var_c, add(var_a, var_b)));
+
+   visit_list_elements(&v, &instructions);
+
+   ASSERT_FALSE(instructions.is_empty());
+
+   ir_instruction *const ir = (ir_instruction *) instructions.pop_head();
+
+   EXPECT_TRUE(instructions.is_empty());
+
+   /* The resulting instruction should be 'c = a + b'. */
+   ir_assignment *const assign = ir->as_assignment();
+   ASSERT_NE((void *)0, assign);
+
+   EXPECT_EQ(var_c, assign->lhs->variable_referenced());
+
+   ir_expression *const expr = assign->rhs->as_expression();
+   ASSERT_NE((void *)0, expr);
+   EXPECT_EQ(ir_binop_add, expr->operation);
+
+   ir_dereference_variable *const deref_a =
+      expr->operands[0]->as_dereference_variable();
+   ir_dereference_variable *const deref_b =
+      expr->operands[1]->as_dereference_variable();
+
+   ASSERT_NE((void *)0, deref_a);
+   EXPECT_EQ(var_a, deref_a->var);
+   ASSERT_NE((void *)0, deref_b);
+   EXPECT_EQ(var_b, deref_b->var);
+}
+
+TEST_F(add_neg_to_sub, a_plus_neg_b)
+{
+   body->emit(assign(var_c, add(var_a, neg(var_b))));
+
+   visit_list_elements(&v, &instructions);
+
+   ASSERT_FALSE(instructions.is_empty());
+
+   ir_instruction *const ir = (ir_instruction *) instructions.pop_head();
+
+   EXPECT_TRUE(instructions.is_empty());
+
+   /* The resulting instruction should be 'c = a - b'. */
+   ir_assignment *const assign = ir->as_assignment();
+   ASSERT_NE((void *)0, assign);
+
+   EXPECT_EQ(var_c, assign->lhs->variable_referenced());
+
+   ir_expression *const expr = assign->rhs->as_expression();
+   ASSERT_NE((void *)0, expr);
+   EXPECT_EQ(ir_binop_sub, expr->operation);
+
+   ir_dereference_variable *const deref_a =
+      expr->operands[0]->as_dereference_variable();
+   ir_dereference_variable *const deref_b =
+      expr->operands[1]->as_dereference_variable();
+
+   ASSERT_NE((void *)0, deref_a);
+   EXPECT_EQ(var_a, deref_a->var);
+   ASSERT_NE((void *)0, deref_b);
+   EXPECT_EQ(var_b, deref_b->var);
+}
+
+TEST_F(add_neg_to_sub, neg_a_plus_b)
+{
+   body->emit(assign(var_c, add(neg(var_a), var_b)));
+
+   visit_list_elements(&v, &instructions);
+
+   ASSERT_FALSE(instructions.is_empty());
+
+   ir_instruction *const ir = (ir_instruction *) instructions.pop_head();
+
+   EXPECT_TRUE(instructions.is_empty());
+
+   /* The resulting instruction should be 'c = b - a'. */
+   ir_assignment *const assign = ir->as_assignment();
+   ASSERT_NE((void *)0, assign);
+
+   EXPECT_EQ(var_c, assign->lhs->variable_referenced());
+
+   ir_expression *const expr = assign->rhs->as_expression();
+   ASSERT_NE((void *)0, expr);
+   EXPECT_EQ(ir_binop_sub, expr->operation);
+
+   ir_dereference_variable *const deref_b =
+      expr->operands[0]->as_dereference_variable();
+   ir_dereference_variable *const deref_a =
+      expr->operands[1]->as_dereference_variable();
+
+   ASSERT_NE((void *)0, deref_a);
+   EXPECT_EQ(var_a, deref_a->var);
+   ASSERT_NE((void *)0, deref_b);
+   EXPECT_EQ(var_b, deref_b->var);
+}
+
+TEST_F(add_neg_to_sub, neg_a_plus_neg_b)
+{
+   body->emit(assign(var_c, add(neg(var_a), neg(var_b))));
+
+   visit_list_elements(&v, &instructions);
+
+   ASSERT_FALSE(instructions.is_empty());
+
+   ir_instruction *const ir = (ir_instruction *) instructions.pop_head();
+
+   EXPECT_TRUE(instructions.is_empty());
+
+   /* The resulting instruction should be 'c = -b - a'. */
+   ir_assignment *const assign = ir->as_assignment();
+   ASSERT_NE((void *)0, assign);
+
+   EXPECT_EQ(var_c, assign->lhs->variable_referenced());
+
+   ir_expression *const expr = assign->rhs->as_expression();
+   ASSERT_NE((void *)0, expr);
+   EXPECT_EQ(ir_binop_sub, expr->operation);
+
+   ir_expression *const neg_b = expr->operands[0]->as_expression();
+   ir_dereference_variable *const deref_a =
+      expr->operands[1]->as_dereference_variable();
+
+   ASSERT_NE((void *)0, deref_a);
+   EXPECT_EQ(var_a, deref_a->var);
+
+   ASSERT_NE((void *)0, neg_b);
+
+   ir_dereference_variable *const deref_b =
+      neg_b->operands[0]->as_dereference_variable();
+
+   ASSERT_NE((void *)0, deref_b);
+   EXPECT_EQ(var_b, deref_b->var);
+}