[Mesa-dev] [PATCH v2 5/5] i965: Shrink brw_vue_map struct.

[Paul Berry]

This patch changes the arrays in brw_vue_map (which only ever contain
values from -1 to 58) from ints to signed chars.  This reduces the
size of the struct from 488 bytes to 136 bytes.
---
 src/mesa/drivers/dri/i965/brw_context.h | 4 ++--
 src/mesa/drivers/dri/i965/brw_vs.c      | 6 ++++++
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_context.h b/src/mesa/drivers/dri/i965/brw_context.h
index 11722e7..506a957 100644
--- a/src/mesa/drivers/dri/i965/brw_context.h
+++ b/src/mesa/drivers/dri/i965/brw_context.h
@@ -368,7 +368,7 @@ struct brw_vue_map {
     * additional processing is applied before storing them in the VUE), the
     * value is -1.
     */
-   int vert_result_to_slot[BRW_VARYING_SLOT_MAX];
+   signed char vert_result_to_slot[BRW_VARYING_SLOT_MAX];
 
    /**
     * Map from VUE slot to gl_varying_slot value.  For slots that do not
@@ -379,7 +379,7 @@ struct brw_vue_map {
     * simplifies code that uses the value stored in slot_to_vert_result to
     * create a bit mask).
     */
-   int slot_to_vert_result[BRW_VARYING_SLOT_MAX];
+   signed char slot_to_vert_result[BRW_VARYING_SLOT_MAX];
 
    /**
     * Total number of VUE slots in use
diff --git a/src/mesa/drivers/dri/i965/brw_vs.c b/src/mesa/drivers/dri/i965/brw_vs.c
index c8ca018..7e941dd 100644
--- a/src/mesa/drivers/dri/i965/brw_vs.c
+++ b/src/mesa/drivers/dri/i965/brw_vs.c
@@ -66,6 +66,12 @@ brw_compute_vue_map(struct brw_context *brw, struct brw_vs_compile *c,
    vue_map->slots_valid = slots_valid;
    int i;
 
+   /* Make sure that the values we store in vue_map->vert_result_to_slot and
+    * vue_map->slot_to_vert_result won't overflow the signed chars that are
+    * used to store them.
+    */
+   STATIC_ASSERT(BRW_VARYING_SLOT_MAX <= 128);
+
    vue_map->num_slots = 0;
    for (i = 0; i < BRW_VARYING_SLOT_MAX; ++i) {
       vue_map->vert_result_to_slot[i] = -1;
-- 
1.8.2