Mesa (master): intel: Simplify stencil detiling arithmetic

[Chad Versace]

Module: Mesa
Branch: master
Commit: dc4c3a31c64aae2c3d76ccbd5bf54d04a1d5d041
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=dc4c3a31c64aae2c3d76ccbd5bf54d04a1d5d041

Author: Chad Versace <chad.versace at linux.intel.com>
Date:   Tue Nov 15 07:10:18 2011 -0800

intel: Simplify stencil detiling arithmetic

When calculating the y offset needed for detiling window system stencil
buffers, replace the term
   region->height * 2 + region->height % 2 - 1
with
   rb->Height - 1 .

The two terms are incidentally equivalent due to some out-of-date,
incorrect code in the Intel DRI2 glue for DDX. (See
intel_process_dri2_buffer_with_separate_stencil(), line ``buffer_height /=
2;``).

Note: This is a candidate for the 7.11 branch (only the intel_span.c hunk).
Signed-off-by: Chad Versace <chad.versace at linux.intel.com>

---

 src/mesa/drivers/dri/intel/intel_fbo.c  |    6 ++----
 src/mesa/drivers/dri/intel/intel_span.c |    3 +--
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/src/mesa/drivers/dri/intel/intel_fbo.c b/src/mesa/drivers/dri/intel/intel_fbo.c
index dbd5163..a724f1d 100644
--- a/src/mesa/drivers/dri/intel/intel_fbo.c
+++ b/src/mesa/drivers/dri/intel/intel_fbo.c
@@ -267,9 +267,8 @@ intel_map_renderbuffer_s8(struct gl_context *ctx,
    irb->map_h = h;
 
    /* Flip the Y axis for the default framebuffer. */
-   int region_h = irb->region->height;
    int y_flip = (rb->Name == 0) ? -1 : 1;
-   int y_bias = (rb->Name == 0) ? (region_h * 2 + region_h % 2 - 1) : 0;
+   int y_bias = (rb->Name == 0) ? (rb->Height - 1) : 0;
 
    irb->map_buffer = malloc(w * h);
    untiled_s8_map = irb->map_buffer;
@@ -442,9 +441,8 @@ intel_unmap_renderbuffer_s8(struct gl_context *ctx,
       uint8_t *tiled_s8_map = irb->region->bo->virtual;
 
       /* Flip the Y axis for the default framebuffer. */
-      int region_h = irb->region->height;
       int y_flip = (rb->Name == 0) ? -1 : 1;
-      int y_bias = (rb->Name == 0) ? (region_h * 2 + region_h % 2 - 1) : 0;
+      int y_bias = (rb->Name == 0) ? (rb->Height - 1) : 0;
 
       for (uint32_t pix_y = 0; pix_y < irb->map_h; pix_y++) {
 	 for (uint32_t pix_x = 0; pix_x < irb->map_w; pix_x++) {
diff --git a/src/mesa/drivers/dri/intel/intel_span.c b/src/mesa/drivers/dri/intel/intel_span.c
index 271d2e1..31f2828 100644
--- a/src/mesa/drivers/dri/intel/intel_span.c
+++ b/src/mesa/drivers/dri/intel/intel_span.c
@@ -141,10 +141,9 @@ intel_set_span_functions(struct intel_context *intel,
    struct intel_renderbuffer *irb = intel_renderbuffer(rb);		\
    uint8_t *buf = irb->region->bo->virtual;				\
    unsigned stride = irb->region->pitch;				\
-   unsigned height = irb->region->height;				\
    bool flip = rb->Name == 0;						\
    int y_scale = flip ? -1 : 1;						\
-   int y_bias = flip ? (height * 2 + height % 2 - 1) : 0;		\
+   int y_bias = flip ? (rb->Height - 1) : 0;				\
 
 #undef Y_FLIP
 #define Y_FLIP(y) (y_scale * (y) + y_bias)