[Mesa-dev] [PATCH 9/9] glsl: optimize (0 cmp x + y) into (-x cmp y).

[Eduardo Lima Mitev]

From: Samuel Iglesias Gonsalvez <siglesias at igalia.com>

The optimization done by commit 34ec1a24d did not take it into account.

Fixes:

dEQP-GLES3.functional.shaders.random.all_features.fragment.20

Signed-off-by: Samuel Iglesias Gonsalvez <siglesias at igalia.com>
---
 src/glsl/opt_algebraic.cpp | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/src/glsl/opt_algebraic.cpp b/src/glsl/opt_algebraic.cpp
index c6f4a9c..8183d57 100644
--- a/src/glsl/opt_algebraic.cpp
+++ b/src/glsl/opt_algebraic.cpp
@@ -578,9 +578,18 @@ ir_algebraic_visitor::handle_expression(ir_expression *ir)
          if (!is_vec_zero(zero))
             continue;
 
-         return new(mem_ctx) ir_expression(ir->operation,
-                                           add->operands[0],
-                                           neg(add->operands[1]));
+         /* Depending of the zero position we want to optimize
+          * (0 cmp x+y) into (-x cmp y) or (x+y cmp 0) into (x cmp -y)
+          */
+         if (add_pos == 1) {
+            return new(mem_ctx) ir_expression(ir->operation,
+                                              neg(add->operands[0]),
+                                              add->operands[1]);
+         } else {
+            return new(mem_ctx) ir_expression(ir->operation,
+                                              add->operands[0],
+                                              neg(add->operands[1]));
+         }
       }
       break;
 
-- 
2.1.3