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static int

cond_for_alpha_func(GLenum func)

{

   switch(func) {

      case GL_GREATER:

         return BRW_CONDITIONAL_G;

      case GL_GEQUAL:

         return BRW_CONDITIONAL_GE;

      case GL_LESS:

         return BRW_CONDITIONAL_L;

      case GL_LEQUAL:

         return BRW_CONDITIONAL_LE;

      case GL_EQUAL:

         return BRW_CONDITIONAL_EQ;

      case GL_NOTEQUAL:

         return BRW_CONDITIONAL_NEQ;

      default:

         assert(!"Not reached");

         return 0;

   }

}

/**

 * Alpha test support for when we compile it into the shader instead

 * of using the normal fixed-function alpha test.

 */

void

fs_visitor::emit_alpha_test()

{

   this->current_annotation = "Alpha test";

   fs_inst *cmp;

   if (c->key.alpha_test_func == GL_ALWAYS)

      return;

   if (c->key.alpha_test_func == GL_NEVER) {

      /* f0.1 = 0 */

      fs_reg some_reg = fs_reg(retype(brw_vec8_grf(0, 0),

                                      BRW_REGISTER_TYPE_UW));

      cmp = emit(CMP(reg_null_f, some_reg, some_reg,

                     BRW_CONDITIONAL_NEQ));

   } else {

      /* RT0 alpha */

      fs_reg color = outputs[0];

      color.reg_offset += 3;

      /* f0.1 &= func(color, ref) */

      cmp = emit(CMP(reg_null_f, color, fs_reg(c->key.alpha_test_ref),

                     cond_for_alpha_func(c->key.alpha_test_func)));

   }

   cmp->predicate = BRW_PREDICATE_NORMAL;

   cmp->flag_subreg = 1;

}