Mesa (master): i965/fs: Add visitor support for nonconstant UBO indices

[Chris Forbes]

Module: Mesa
Branch: master
Commit: ad9fce6811894e53819709a861624b7c642b234d
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=ad9fce6811894e53819709a861624b7c642b234d

Author: Chris Forbes <chrisf at ijw.co.nz>
Date:   Sun May 18 12:38:57 2014 +1200

i965/fs: Add visitor support for nonconstant UBO indices

Signed-off-by: Chris Forbes <chrisf at ijw.co.nz>

---

 src/mesa/drivers/dri/i965/brw_fs_visitor.cpp |   30 +++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
index f72909e..5d439fc 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp
@@ -900,10 +900,34 @@ fs_visitor::visit(ir_expression *ir)
       /* This IR node takes a constant uniform block and a constant or
        * variable byte offset within the block and loads a vector from that.
        */
-      ir_constant *uniform_block = ir->operands[0]->as_constant();
+      ir_constant *const_uniform_block = ir->operands[0]->as_constant();
       ir_constant *const_offset = ir->operands[1]->as_constant();
-      fs_reg surf_index = fs_reg(prog_data->base.binding_table.ubo_start +
-                                 uniform_block->value.u[0]);
+      fs_reg surf_index;
+
+      if (const_uniform_block) {
+         /* The block index is a constant, so just emit the binding table entry
+          * as an immediate.
+          */
+         surf_index = fs_reg(prog_data->base.binding_table.ubo_start +
+                                 const_uniform_block->value.u[0]);
+      } else {
+         /* The block index is not a constant. Evaluate the index expression
+          * per-channel and add the base UBO index; the generator will select
+          * a value from any live channel.
+          */
+         surf_index = fs_reg(this, glsl_type::uint_type);
+         emit(ADD(surf_index, op[0],
+                  fs_reg(prog_data->base.binding_table.ubo_start)))
+            ->force_writemask_all = true;
+
+         /* Assume this may touch any UBO. It would be nice to provide
+          * a tighter bound, but the array information is already lowered away.
+          */
+         brw_mark_surface_used(&prog_data->base,
+                               prog_data->base.binding_table.ubo_start +
+                               shader_prog->NumUniformBlocks - 1);
+      }
+
       if (const_offset) {
          fs_reg packed_consts = fs_reg(this, glsl_type::float_type);
          packed_consts.type = result.type;