From: Ian Romanick <ian.d.roman...@intel.com>
Since our logic values are 0.0 (false) and 1.0 (true), 1.0 - x
accurately implements logical not.
---
src/mesa/program/ir_to_mesa.cpp | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/src/mesa/program/ir_to_mesa.cpp b/src/mesa/program/ir_to_mesa.cpp
index c76dc8d..57e7d67 100644
--- a/src/mesa/program/ir_to_mesa.cpp
+++ b/src/mesa/program/ir_to_mesa.cpp
@@ -1135,7 +1135,13 @@ ir_to_mesa_visitor::visit(ir_expression *ir)
switch (ir->operation) {
case ir_unop_logic_not:
- emit(ir, OPCODE_SEQ, result_dst, op[0], src_reg_for_float(0.0));
+ /* Previously 'SEQ dst, src, 0.0' was used for this. However, many
+ * older GPUs implement SEQ using multiple instructions (i915 uses two
+ * SGE instructions and a MUL instruction). Since our logic values are
+ * 0.0 and 1.0, 1-x also implements !x.
+ */
+ op[0].negate = ~op[0].negate;
+ emit(ir, OPCODE_ADD, result_dst, op[0], src_reg_for_float(1.0));
break;
case ir_unop_neg:
op[0].negate = ~op[0].negate;
--
1.7.4.4
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