glsl: Distribute ir_unop_neg over ir_binop_mul of a constantbool-optimizations-v5

1 files changed, 21 insertions, 0 deletions

diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
index 9a3c10cc2b4..efa955c35fe 100644
--- a/src/glsl/opt_algebraic.cpp
+++ b/src/glsl/opt_algebraic.cpp
@@ -443,6 +443,27 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
       if (op_expr[0]->operation == ir_unop_neg) {
          return op_expr[0]->operands[0];
       }
+
+      /* Replace -(x * constant) with (x * -constant).
+       */
+      if (op_expr[0]->operation == ir_binop_mul) {
+         for (i = 0; i < 2; i++) {
+            if (op_expr[0]->operands[i]->as_constant()) {
+               ir_expression *const tmp_expr =
+                  new(mem_ctx) ir_expression(ir_unop_neg,
+                                             op_expr[0]->operands[i]);
+
+               /* Constant-fold the expression now to (possibly) save an
+                * interation through the optimization loop.
+                */
+               op_expr[0]->operands[i] =
+                  tmp_expr->constant_expression_value();
+
+               assert(op_expr[0]->operands[i] != NULL);
+               return op_expr[0];
+            }
+         }
+      }
       break;
 
    case ir_unop_exp: