[Mesa-dev] [PATCH] st/mesa: fix weird UCMP opcode use for bool ubo load

[sroland at vmware.com]

From: Roland Scheidegger <sroland at vmware.com>

I don't know what this code was trying to do but whatever it was it couldn't
have worked since negation of integer boolean inputs while not specified as
outright illegal (not yet at least) won't do anything since it doesn't affect
the result of comparison with zero at all. In fact it looks like the whole
instruction can just be omitted.
---
 src/mesa/state_tracker/st_glsl_to_tgsi.cpp |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
index f2eb3e7..08b2d7a 100644
--- a/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
+++ b/src/mesa/state_tracker/st_glsl_to_tgsi.cpp
@@ -1945,8 +1945,6 @@ glsl_to_tgsi_visitor::visit(ir_expression *ir)
 
       if (ir->type->base_type == GLSL_TYPE_BOOL) {
          emit(ir, TGSI_OPCODE_USNE, result_dst, cbuf, st_src_reg_for_int(0));
-         result_src.negate = 1;
-         emit(ir, TGSI_OPCODE_UCMP, result_dst, result_src, st_src_reg_for_int(~0), st_src_reg_for_int(0));
       } else {
          emit(ir, TGSI_OPCODE_MOV, result_dst, cbuf);
       }
@@ -2388,8 +2386,8 @@ glsl_to_tgsi_visitor::visit(ir_assignment *ir)
          if (native_integers) {
             /* This is necessary because TGSI's CMP instruction expects the
              * condition to be a float, and we store booleans as integers.
-             * If TGSI had a UCMP instruction or similar, this extra
-             * instruction would not be necessary.
+             * TODO: really want to avoid i2f path and use UCMP. Requires
+             * changes to process_move_condition though too.
              */
             condition_temp = get_temp(glsl_type::vec4_type);
             condition.negate = 0;
-- 
1.7.9.5