[Mesa-dev] [PATCH 1/2] mesa/st: add support for dynamic ubo selection

[Ilia Mirkin]

Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---

With ChrisF's patches to add support for this in core mesa, this generates
code like:

FRAG
DCL OUT[0], COLOR
DCL CONST[0]
DCL CONST[1][0]
DCL CONST[2][0]
DCL CONST[3][0]
DCL CONST[4][0]
DCL TEMP[0], LOCAL
DCL ADDR[0..1]
IMM[0] UINT32 {0, 0, 0, 0}
IMM[1] INT32 {1, 0, 0, 0}
  0: UADD TEMP[0].x, CONST[0].xxxx, IMM[1].xxxx
  1: UARL ADDR[1].x, TEMP[0].xxxx
  2: UARL ADDR[1].x, TEMP[0].xxxx
  3: MOV TEMP[0], CONST[ADDR[1].x][0]
  4: MOV OUT[0], TEMP[0]
  5: END

Not sure what the deal is with the two UARL's, but nouveau's backend removes
one of them pretty easily. I assume others handle this too.

Unfortunately the core patches aren't quite ready yet, but this patch doesn't
regress anything.

 src/mesa/state_tracker/st_glsl_to_tgsi.cpp | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index 9bc7500..3202c56 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -1947,16 +1947,16 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
       break;
 
    case ir_binop_ubo_load: {
-      ir_constant *uniform_block = ir->operands[0]->as_constant();
+      ir_constant *const_uniform_block = ir->operands[0]->as_constant();
       ir_constant *const_offset_ir = ir->operands[1]->as_constant();
       unsigned const_offset = const_offset_ir ? const_offset_ir->value.u[0] : 0;
+      unsigned const_block = const_uniform_block ? const_uniform_block->value.u[0] + 1 : 0;
       st_src_reg index_reg = get_temp(glsl_type::uint_type);
       st_src_reg cbuf;
 
       cbuf.type = glsl_type::vec4_type->base_type;
       cbuf.file = PROGRAM_CONSTANT;
       cbuf.index = 0;
-      cbuf.index2D = uniform_block->value.u[0] + 1;
       cbuf.reladdr = NULL;
       cbuf.negate = 0;
       
@@ -1966,7 +1966,6 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
          /* Constant index into constant buffer */
          cbuf.reladdr = NULL;
          cbuf.index = const_offset / 16;
-         cbuf.has_index2 = true;
       }
       else {
          /* Relative/variable index into constant buffer */
@@ -1976,6 +1975,21 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
          memcpy(cbuf.reladdr, &index_reg, sizeof(index_reg));
       }
 
+      if (const_uniform_block) {
+         /* Constant constant buffer */
+         cbuf.reladdr2 = NULL;
+         cbuf.index2D = const_block;
+         cbuf.has_index2 = true;
+      }
+      else {
+         /* Relative/variable constant buffer */
+         emit(ir, TGSI_OPCODE_UADD, st_dst_reg(index_reg), op[0],
+              st_src_reg_for_int(1));
+         cbuf.reladdr2 = ralloc(mem_ctx, st_src_reg);
+         memcpy(cbuf.reladdr2, &index_reg, sizeof(index_reg));
+         cbuf.has_index2 = true;
+      }
+
       cbuf.swizzle = swizzle_for_size(ir->type->vector_elements);
       cbuf.swizzle += MAKE_SWIZZLE4(const_offset % 16 / 4,
                                     const_offset % 16 / 4,
-- 
1.8.5.5