Mesa (lp-binning): llvmpipe: added comment about lookup-tables vs. computation

[Brian Paul]

Module: Mesa
Branch: lp-binning
Commit: 12ba9e99db51a4a9e2e28a0574ef59f6548d8a84
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=12ba9e99db51a4a9e2e28a0574ef59f6548d8a84

Author: Brian Paul <brianp at vmware.com>
Date:   Fri Jan 15 11:26:35 2010 -0700

llvmpipe: added comment about lookup-tables vs. computation

---

 src/gallium/drivers/llvmpipe/lp_rast_tri.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/src/gallium/drivers/llvmpipe/lp_rast_tri.c b/src/gallium/drivers/llvmpipe/lp_rast_tri.c
index 9c3f699..92769be 100644
--- a/src/gallium/drivers/llvmpipe/lp_rast_tri.c
+++ b/src/gallium/drivers/llvmpipe/lp_rast_tri.c
@@ -40,6 +40,9 @@
  * Map an index in [0,15] to an x,y position, multiplied by 4.
  * This is used to get the position of each subtile in a 4x4
  * grid of edge step values.
+ * Note: we can use some bit twiddling to compute these values instead
+ * of using a look-up table, but there's no measurable performance
+ * difference.
  */
 static const int pos_table4[16][2] = {
    { 0, 0 },