From: Matt Turner <mattst88@gmail.com>
Date: Mon, 24 Feb 2014 23:00:45 +0000 (-0800)
Subject: glsl: Optimize lrp(x, 0, a) into x - (x * a).
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=d5fa8a956211692441b9c3ffc97b7486599ab3a3;p=mesa.git

glsl: Optimize lrp(x, 0, a) into x - (x * a).

Helps one program in shader-db:

instructions in affected programs:     96 -> 92 (-4.17%)

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
---

diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
index 28f95a44c7f..778638cf261 100644
--- a/src/glsl/opt_algebraic.cpp
+++ b/src/glsl/opt_algebraic.cpp
@@ -570,6 +570,8 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
          return ir->operands[0];
       } else if (is_vec_zero(op_const[0])) {
          return mul(ir->operands[1], ir->operands[2]);
+      } else if (is_vec_zero(op_const[1])) {
+         return add(ir->operands[0], neg(mul(ir->operands[0], ir->operands[2])));
       }
       break;