src/gallium/drivers/llvmpipe/lp_bld_alpha.c

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/**
 * Alpha testing to LLVM IR translation.
 *
 * @author Jose Fonseca <jfonseca@vmware.com>
 */

#include "pipe/p_state.h"
#include "util/u_format.h"

#include "gallivm/lp_bld_type.h"
#include "gallivm/lp_bld_const.h"
#include "gallivm/lp_bld_arit.h"
#include "gallivm/lp_bld_conv.h"
#include "gallivm/lp_bld_logic.h"
#include "gallivm/lp_bld_flow.h"
#include "gallivm/lp_bld_debug.h"

#include "lp_bld_alpha.h"


void
lp_build_alpha_test(struct gallivm_state *gallivm,
                    unsigned func,
                    struct lp_type type,
                    const struct util_format_description *cbuf_format_desc,
                    struct lp_build_mask_context *mask,
                    LLVMValueRef alpha,
                    LLVMValueRef ref,
                    boolean do_branch)
{
   struct lp_build_context bld;
   LLVMValueRef test;

   lp_build_context_init(&bld, gallivm, type);

   /*
    * Alpha testing needs to be done in the color buffer precision.
    *
    * TODO: Ideally, instead of duplicating the color conversion code, we would do
    * alpha testing after converting the output colors, but that's not very
    * convenient, because it needs to be done before depth testing.  Hopefully
    * LLVM will detect and remove the duplicate expression.
    *
    * FIXME: This should be generalized to formats other than rgba8 variants.
    */
   if (type.floating &&
       util_format_is_rgba8_variant(cbuf_format_desc)) {
      const unsigned dst_width = 8;

      alpha = lp_build_clamp(&bld, alpha, bld.zero, bld.one);
      ref   = lp_build_clamp(&bld, ref,   bld.zero, bld.one);

      alpha = lp_build_clamped_float_to_unsigned_norm(gallivm, type, dst_width, alpha);
      ref   = lp_build_clamped_float_to_unsigned_norm(gallivm, type, dst_width, ref);

      type.floating = 0;
      lp_build_context_init(&bld, gallivm, type);
   }

   test = lp_build_cmp(&bld, func, alpha, ref);

   lp_build_name(test, "alpha_mask");

   lp_build_mask_update(mask, test);

   if (do_branch)
      lp_build_mask_check(mask);
}