[Mesa-dev] [PATCH] glsl: Optimize logic operation A || (A && B) v2

[thomashelland90 at gmail.com]

From: Thomas Helland <thomashelland90 at gmail.com>

Let's cut the needless A && B here.
Gives some effect on a clean shader-db with
some extra shaders from TF2 and portal.

helped: shaders/tf2/2042.shader_test fs16:        23 -> 21 (-8.70%)
helped: shaders/tf2/2042.shader_test fs8:         23 -> 21 (-8.70%)
helped: shaders/tf2/4624.shader_test fs16:        21 -> 19 (-9.52%)
helped: shaders/tf2/4624.shader_test fs8:         21 -> 19 (-9.52%)
helped: shaders/tf2/763.shader_test fs16:         23 -> 21 (-8.70%)
helped: shaders/tf2/763.shader_test fs8:          23 -> 21 (-8.70%)

HURT:   shaders/orbital_explorer.shader_test vs:  1049 -> 1052 (0.29%)

total instructions in shared programs: 758979 -> 758970 (-0.00%)
instructions in affected programs:     1183 -> 1174 (-0.76%)
GAINED:                                0
LOST:                                  0

v1 -> v2: Correct the comments, return A instead of A && B

Interestingly, returning A instead of A && B does not improve
the results in shader-db like I would've expected.
I would've expected it to cut of another instruction or so.

Signed-off-by: Thomas Helland <thomashelland90 at gmail.com>
---
 src/glsl/opt_algebraic.cpp | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
index ac7514a..fe7166d 100644
--- a/src/glsl/opt_algebraic.cpp
+++ b/src/glsl/opt_algebraic.cpp
@@ -588,7 +588,18 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
       } else if (ir->operands[0]->equals(ir->operands[1])) {
          /* (a || a) == a */
          return ir->operands[0];
+      } else if (op_expr[0] && op_expr[0]->operation == ir_binop_logic_and &&
+                    (op_expr[0]->operands[0]->equals(op_expr[1]) || 
+                     op_expr[0]->operands[1]->equals(op_expr[1]))) {
+         /* (A && B) || A == A or (B && A) || A == A */
+         return ir->operands[1];
+      } else if (op_expr[1] && op_expr[1]->operation == ir_binop_logic_and &&
+                    (op_expr[1]->operands[0]->equals(op_expr[0]) || 
+                     op_expr[1]->operands[1]->equals(op_expr[0]))) {
+         /* A || (A && B) == A or A || (B && A) == A */
+         return ir->operands[0];
       }
+
       break;
 
    case ir_binop_pow:
-- 
2.0.0