src/gallium/drivers/llvmpipe/lp_bld_alpha.c

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  27
  28 /**
  29  * Alpha testing to LLVM IR translation.
  30  *
  31  * @author Jose Fonseca <jfonseca@vmware.com>
  32  */
  33
  34 #include "pipe/p_state.h"
  35 #include "util/format/u_format.h"
  36
  37 #include "gallivm/lp_bld_type.h"
  38 #include "gallivm/lp_bld_const.h"
  39 #include "gallivm/lp_bld_arit.h"
  40 #include "gallivm/lp_bld_conv.h"
  41 #include "gallivm/lp_bld_logic.h"
  42 #include "gallivm/lp_bld_flow.h"
  43 #include "gallivm/lp_bld_debug.h"
  44
  45 #include "lp_bld_alpha.h"
  46
  47
  48 void
  49 lp_build_alpha_test(struct gallivm_state *gallivm,
  50                     unsigned func,
  51                     struct lp_type type,
  52                     const struct util_format_description *cbuf_format_desc,
  53                     struct lp_build_mask_context *mask,
  54                     LLVMValueRef alpha,
  55                     LLVMValueRef ref,
  56                     boolean do_branch)
  57 {
  58    struct lp_build_context bld;
  59    LLVMValueRef test;
  60
  61    lp_build_context_init(&bld, gallivm, type);
  62
  63    /*
  64     * Alpha testing needs to be done in the color buffer precision.
  65     *
  66     * TODO: Ideally, instead of duplicating the color conversion code, we would do
  67     * alpha testing after converting the output colors, but that's not very
  68     * convenient, because it needs to be done before depth testing.  Hopefully
  69     * LLVM will detect and remove the duplicate expression.
  70     *
  71     * FIXME: This should be generalized to formats other than rgba8 variants.
  72     */
  73    if (type.floating &&
  74        util_format_is_rgba8_variant(cbuf_format_desc)) {
  75       const unsigned dst_width = 8;
  76
  77       alpha = lp_build_clamp(&bld, alpha, bld.zero, bld.one);
  78       ref   = lp_build_clamp(&bld, ref,   bld.zero, bld.one);
  79
  80       alpha = lp_build_clamped_float_to_unsigned_norm(gallivm, type, dst_width, alpha);
  81       ref   = lp_build_clamped_float_to_unsigned_norm(gallivm, type, dst_width, ref);
  82
  83       type.floating = 0;
  84       lp_build_context_init(&bld, gallivm, type);
  85    }
  86
  87    test = lp_build_cmp(&bld, func, alpha, ref);
  88
  89    lp_build_name(test, "alpha_mask");
  90
  91    lp_build_mask_update(mask, test);
  92
  93    if (do_branch)
  94       lp_build_mask_check(mask);
  95 }