+/*
+ * Combined log2 and brilinear lod computation.
+ *
+ * It's in all identical to calling lp_build_fast_log2() and
+ * lp_build_brilinear_lod() above, but by combining we can compute the interger
+ * and fractional part independently.
+ */
+static void
+lp_build_brilinear_rho(struct lp_build_context *bld,
+ LLVMValueRef rho,
+ double factor,
+ LLVMValueRef *out_lod_ipart,
+ LLVMValueRef *out_lod_fpart)
+{
+ LLVMValueRef lod_ipart;
+ LLVMValueRef lod_fpart;
+
+ const double pre_factor = (2*factor - 0.5)/(M_SQRT2*factor);
+ const double post_offset = 1 - 2*factor;
+
+ assert(bld->type.floating);
+
+ assert(lp_check_value(bld->type, rho));
+
+ /*
+ * The pre factor will make the intersections with the exact powers of two
+ * happen precisely where we want then to be, which means that the integer
+ * part will not need any post adjustments.
+ */
+ rho = lp_build_mul(bld, rho,
+ lp_build_const_vec(bld->type, pre_factor));
+
+ /* ipart = ifloor(log2(rho)) */
+ lod_ipart = lp_build_extract_exponent(bld, rho, 0);
+
+ /* fpart = rho / 2**ipart */
+ lod_fpart = lp_build_extract_mantissa(bld, rho);
+
+ lod_fpart = lp_build_mul(bld, lod_fpart,
+ lp_build_const_vec(bld->type, factor));
+
+ lod_fpart = lp_build_add(bld, lod_fpart,
+ lp_build_const_vec(bld->type, post_offset));
+
+ /*
+ * Like lp_build_brilinear_lod, it's not necessary to clamp lod_fpart since:
+ * - the above expression will never produce numbers greater than one.
+ * - the mip filtering branch is only taken if lod_fpart is positive
+ */
+
+ *out_lod_ipart = lod_ipart;
+ *out_lod_fpart = lod_fpart;
+}
+
+