From: Thomas Helland <thomashellan...@gmail.com>
Since we lower A - B to A + neg(B) on some architectures
lets add a optimization for this pattern.
This yields some gains in a shader-db run with extra shaders
added from Team Fortress 2 and Portal.
helped: shaders/tf2/1684.shader_test fs16: 62 -> 60 (-3.23%)
helped: shaders/tf2/1684.shader_test fs8: 62 -> 60 (-3.23%)
helped: shaders/tf2/5861.shader_test fs16: 68 -> 66 (-2.94%)
helped: shaders/tf2/5861.shader_test fs8: 68 -> 66 (-2.94%)
helped: shaders/tf2/5986.shader_test fs16: 68 -> 66 (-2.94%)
helped: shaders/tf2/5986.shader_test fs8: 68 -> 66 (-2.94%)
helped: shaders/tf2/6926.shader_test fs16: 62 -> 60 (-3.23%)
helped: shaders/tf2/6926.shader_test fs8: 62 -> 60 (-3.23%)
total instructions in shared programs: 731050 -> 731034 (-0.00%)
instructions in affected programs: 520 -> 504 (-3.08%)
GAINED: 0
LOST: 0
Signed-off-by: Thomas Helland <thomashelland90 at gmail.com>
---
src/glsl/opt_algebraic.cpp | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
index 4008fe7..21bf332 100644
--- a/src/glsl/opt_algebraic.cpp
+++ b/src/glsl/opt_algebraic.cpp
@@ -364,6 +364,15 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
if (is_vec_zero(op_const[1]))
return ir->operands[0];
+ /* X + neg(X) == 0 */
+ if (op_expr[1] && op_expr[1]->operation == ir_unop_neg &&
+ ir->operands[0]->equals(op_expr[1]->operands[0]))
+ return ir_constant::zero(ir, ir->type);
+ /* neg(X) + X == 0 */
+ if (op_expr[0] && op_expr[0]->operation == ir_unop_neg &&
+ ir->operands[1]->equals(op_expr[0]->operands[0]))
+ return ir_constant::zero(ir, ir->type);
+
/* Reassociate addition of constants so that we can do constant
* folding.
*/
--
2.0.3
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