ir_constant_expression: Add support for the "step" builtin.

diff --git a/src/glsl/ir_constant_expression.cpp b/src/glsl/ir_constant_expression.cpp
index c939690129a25a5fd16bbb9b7fb8ec474554e73f..5485d79a88f1a4c2f4e36226cf23adaaf72be59c 100644 (file)
--- a/src/glsl/ir_constant_expression.cpp
+++ b/src/glsl/ir_constant_expression.cpp
@@ -1045,7 +1045,11 @@ ir_call::constant_expression_value()
    } else if (strcmp(callee, "sqrt") == 0) {
       expr = new(mem_ctx) ir_expression(ir_unop_sqrt, type, op[0], NULL);
    } else if (strcmp(callee, "step") == 0) {
-      return NULL; /* FINISHME: implement this */
+      assert(op[0]->type->is_float() && op[1]->type->is_float());
+      /* op[0] (edge) may be either a scalar or a vector */
+      const unsigned c0_inc = op[0]->type->is_scalar() ? 0 : 1;
+      for (unsigned c = 0, c0 = 0; c < type->components(); c0 += c0_inc, c++)
+        data.f[c] = (op[1]->value.f[c] < op[0]->value.f[c0]) ? 0.0 : 1.0;
    } else if (strcmp(callee, "tan") == 0) {
       assert(op[0]->type->is_float());
       for (unsigned c = 0; c < op[0]->type->components(); c++)