[Mesa-dev] [PATCH 09/15] glsl/standalone: Optimize add-of-neg to subtract

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

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

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
---
 src/compiler/glsl/standalone.cpp | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/src/compiler/glsl/standalone.cpp b/src/compiler/glsl/standalone.cpp
index 6b1c2ce..c4b6854 100644
--- a/src/compiler/glsl/standalone.cpp
+++ b/src/compiler/glsl/standalone.cpp
@@ -38,6 +38,37 @@
 #include "standalone.h"
 #include "util/string_to_uint_map.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[i] = op->operands[0];
+            break;
+         }
+      }
+
+      return visit_continue;
+   }
+};
+
 static const struct standalone_options *options;
 
 static void
@@ -437,6 +468,9 @@ 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);
       }
-- 
2.5.5