Mesa (glsl2): glsl2: Constant-fold assignment conditions.

[Eric Anholt]

Module: Mesa
Branch: glsl2
Commit: 14f8e16132409f38656e4874aa53bc471977f9ad
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=14f8e16132409f38656e4874aa53bc471977f9ad

Author: Eric Anholt <eric at anholt.net>
Date:   Tue Jul 20 11:43:28 2010 -0700

glsl2: Constant-fold assignment conditions.

---

 src/glsl/ir_constant_folding.cpp |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/src/glsl/ir_constant_folding.cpp b/src/glsl/ir_constant_folding.cpp
index 2daa6fd..66a92e9 100644
--- a/src/glsl/ir_constant_folding.cpp
+++ b/src/glsl/ir_constant_folding.cpp
@@ -167,6 +167,19 @@ ir_constant_folding_visitor::visit(ir_assignment *ir)
       ir->rhs = const_val;
    else
       ir->rhs->accept(this);
+
+   if (ir->condition) {
+      /* If the condition is constant, either remove the condition or
+       * remove the never-executed assignment.
+       */
+      const_val = ir->condition->constant_expression_value();
+      if (const_val) {
+	 if (const_val->value.b[0])
+	    ir->condition = NULL;
+	 else
+	    ir->remove();
+      }
+   }
 }