[Mesa-dev] [PATCH 01/13] i965: Simplify Broadwell's 3DSTATE_MULTISAMPLE sample count handling.

[Kenneth Graunke]

These enumerations are simply log2 of the number of multisamples shifted
by a bit, so we can calculate them using ffs() in a lot less code.

Suggested by Eric Anholt.

Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/mesa/drivers/dri/i965/gen8_multisample_state.c | 26 +++-------------------
 1 file changed, 3 insertions(+), 23 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/gen8_multisample_state.c b/src/mesa/drivers/dri/i965/gen8_multisample_state.c
index 64c7208..bfe0d5b 100644
--- a/src/mesa/drivers/dri/i965/gen8_multisample_state.c
+++ b/src/mesa/drivers/dri/i965/gen8_multisample_state.c
@@ -33,33 +33,13 @@
 void
 gen8_emit_3dstate_multisample(struct brw_context *brw, unsigned num_samples)
 {
-   uint32_t number_of_multisamples = 0;
+   assert(num_samples <= 16);
 
-   switch (num_samples) {
-   case 0:
-   case 1:
-      number_of_multisamples = MS_NUMSAMPLES_1;
-      break;
-   case 2:
-      number_of_multisamples = MS_NUMSAMPLES_2;
-      break;
-   case 4:
-      number_of_multisamples = MS_NUMSAMPLES_4;
-      break;
-   case 8:
-      number_of_multisamples = MS_NUMSAMPLES_8;
-      break;
-   case 16:
-      number_of_multisamples = MS_NUMSAMPLES_16;
-      break;
-   default:
-      assert(!"Unrecognized num_samples in gen8_emit_3dstate_multisample");
-      break;
-   }
+   unsigned log2_samples = ffs(MAX2(num_samples, 1)) - 1;
 
    BEGIN_BATCH(2);
    OUT_BATCH(GEN8_3DSTATE_MULTISAMPLE << 16 | (2 - 2));
-   OUT_BATCH(MS_PIXEL_LOCATION_CENTER | number_of_multisamples);
+   OUT_BATCH(MS_PIXEL_LOCATION_CENTER | log2_samples << 1);
    ADVANCE_BATCH();
 }
 
-- 
1.8.4.2