[Mesa-dev] [PATCH 22/22] glsl: Remove useless abs based on range analysis

[Thomas Helland]

---
 src/glsl/opt_minmax.cpp | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/glsl/opt_minmax.cpp b/src/glsl/opt_minmax.cpp
index 8cf0fe5..3d3cfff 100644
--- a/src/glsl/opt_minmax.cpp
+++ b/src/glsl/opt_minmax.cpp
@@ -80,6 +80,8 @@ public:
 
    ir_rvalue *opt_compare(ir_expression *expr, minmax_range baserange);
 
+   ir_rvalue *opt_abs(ir_expression *expr, minmax_range baserange);
+
    ir_rvalue *opt_undefined_behaviour(ir_expression *expr, minmax_range baserange);
 
    void handle_rvalue(ir_rvalue **rvalue);
@@ -598,6 +600,25 @@ ir_minmax_visitor::opt_undefined_behaviour(ir_expression *expr, minmax_range bas
 }
 
 /**
+ * Removes useless abs.
+ *
+ * @param baserange the range of this expression that will be used by its
+ * parents, if this is applicable
+ */
+ir_rvalue *
+ir_minmax_visitor::opt_abs(ir_expression *expr, minmax_range baserange)
+{
+   // Get the range for the operand
+   minmax_range r0 = get_range(expr->operands[0]);
+
+   // Operand >= 0.0 lets us eliminate the abs
+   if (IS_CONSTANT(r0.low, >=, 0.0f))
+      return expr->operands[0];
+
+   return expr;
+}
+
+/**
  * Eliminates saturate-operations that are defined to either
  * 0 or 1 based on the operand being less than zero, or larger than 1.
  *
@@ -863,6 +884,9 @@ ir_minmax_visitor::handle_rvalue(ir_rvalue **rvalue)
    if (expr->operation == ir_unop_saturate)
       new_rvalue = opt_saturate(expr, minmax_range());
 
+   if (expr->operation == ir_unop_abs)
+      new_rvalue = opt_abs(expr, minmax_range());
+
    if (expr->operation == ir_binop_equal ||
        expr->operation == ir_binop_lequal ||
        expr->operation == ir_binop_gequal ||
-- 
2.2.1