i965/fs: Factor out texture offset bitfield computation.

We'll want to reuse this for the VS, and it's complex enough that I'd
rather not cut and paste it.

Signed-off-by: Kenneth Graunke <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>

1 files changed, 23 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_shader.cpp b/src/mesa/drivers/dri/i965/brw_shader.cpp
index 33c9ae57ac2..1845c3d7618 100644
--- a/src/mesa/drivers/dri/i965/brw_shader.cpp
+++ b/src/mesa/drivers/dri/i965/brw_shader.cpp
@@ -239,3 +239,26 @@ brw_math_function(enum opcode op)
       return 0;
    }
 }
+
+uint32_t
+brw_texture_offset(ir_constant *offset)
+{
+   assert(offset != NULL);
+
+   signed char offsets[3];
+   for (unsigned i = 0; i < offset->type->vector_elements; i++)
+      offsets[i] = (signed char) offset->value.i[i];
+
+   /* Combine all three offsets into a single unsigned dword:
+    *
+    *    bits 11:8 - U Offset (X component)
+    *    bits  7:4 - V Offset (Y component)
+    *    bits  3:0 - R Offset (Z component)
+    */
+   unsigned offset_bits = 0;
+   for (unsigned i = 0; i < offset->type->vector_elements; i++) {
+      const unsigned shift = 4 * (2 - i);
+      offset_bits |= (offsets[i] << shift) & (0xF << shift);
+   }
+   return offset_bits;
+}