convert: Add SSE implementation for sc12

Implementation uses SSSE3 intructions to perform 12-bit
sample pack/unpack operations to/from standard 16 and 32
bit host values. Input/output shuffle orderings for a
single 128-bit SSE register with 16-bit integers shown
below.

   16-bit interleaved I/Q
  ---------------------------------------
 | Q3 | I3 | Q2 | I2 | Q1 | I1 | Q0 | I0 | Input
  ---------------------------------------
 | 127                                 0 |

     12-bit packed I/Q byteswapped
      -----------------------
     |   I0   |   Q0   |  I1 | 0
     |-----------------------|
     | I1 |  Q1  |  I2  | Q2 |             Output
     |-----------------------|
     | Q2  |   I3   |   Q3   |
     |-----------------------|
     |        Unused         | 3
      -----------------------
     31                     0

Fixes: #1740, #966
Related: #1739

1 files changed, 112 insertions, 0 deletions

diff --git a/host/lib/convert/convert_unpack_sc12.hpp b/host/lib/convert/convert_unpack_sc12.hpp
new file mode 100644
index 000000000..46e7d58fb
--- /dev/null
+++ b/host/lib/convert/convert_unpack_sc12.hpp
@@ -0,0 +1,112 @@
+//
+// Copyright 2017 Ettus Research LLC
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+//
+
+#include <type_traits>
+#include <uhd/utils/byteswap.hpp>
+#include "convert_common.hpp"
+
+using namespace uhd::convert;
+
+typedef uint32_t (*tohost32_type)(uint32_t);
+
+/* C language specification requires this to be packed
+ * (i.e., line0, line1, line2 will be in adjacent memory locations).
+ * If this was not true, we'd need compiler flags here to specify
+ * alignment/packing.
+ */
+struct item32_sc12_3x
+{
+    item32_t line0;
+    item32_t line1;
+    item32_t line2;
+};
+
+/*
+ * convert_sc12_item32_3_to_star_4 takes in 3 lines with 32 bit each
+ * and converts them 4 samples of type 'std::complex<type>'.
+ * The structure of the 3 lines is as follows:
+ *  _ _ _ _ _ _ _ _
+ * |_ _ _1_ _ _|_ _|
+ * |_2_ _ _|_ _ _3_|
+ * |_ _|_ _ _4_ _ _|
+ *
+ * The numbers mark the position of one complex sample.
+ */
+template <typename type, tohost32_type tohost>
+void convert_sc12_item32_3_to_star_4
+(
+    const item32_sc12_3x &input,
+    std::complex<type> &out0,
+    std::complex<type> &out1,
+    std::complex<type> &out2,
+    std::complex<type> &out3,
+    const double scalar,
+    typename std::enable_if<std::is_floating_point<type>::value>::type* = NULL
+)
+{
+    //step 0: extract the lines from the input buffer
+    const item32_t line0 = tohost(input.line0);
+    const item32_t line1 = tohost(input.line1);
+    const item32_t line2 = tohost(input.line2);
+    const uint64_t line01 = (uint64_t(line0) << 32) | line1;
+    const uint64_t line12 = (uint64_t(line1) << 32) | line2;
+
+    //step 1: shift out and mask off the individual numbers
+    const type i0 = type(int16_t((line0 >> 16) & 0xfff0)*scalar);
+    const type q0 = type(int16_t((line0 >> 4) & 0xfff0)*scalar);
+
+    const type i1 = type(int16_t((line01 >> 24) & 0xfff0)*scalar);
+    const type q1 = type(int16_t((line1 >> 12) & 0xfff0)*scalar);
+
+    const type i2 = type(int16_t((line1 >> 0) & 0xfff0)*scalar);
+    const type q2 = type(int16_t((line12 >> 20) & 0xfff0)*scalar);
+
+    const type i3 = type(int16_t((line2 >> 8) & 0xfff0)*scalar);
+    const type q3 = type(int16_t((line2 << 4) & 0xfff0)*scalar);
+
+    //step 2: load the outputs
+    out0 = std::complex<type>(i0, q0);
+    out1 = std::complex<type>(i1, q1);
+    out2 = std::complex<type>(i2, q2);
+    out3 = std::complex<type>(i3, q3);
+}
+
+template <typename type, tohost32_type tohost>
+void convert_sc12_item32_3_to_star_4
+(
+    const item32_sc12_3x &input,
+    std::complex<type> &out0,
+    std::complex<type> &out1,
+    std::complex<type> &out2,
+    std::complex<type> &out3,
+    const double,
+    typename std::enable_if<std::is_integral<type>::value>::type* = NULL
+)
+{
+    //step 0: extract the lines from the input buffer
+    const item32_t line0 = tohost(input.line0);
+    const item32_t line1 = tohost(input.line1);
+    const item32_t line2 = tohost(input.line2);
+    const uint64_t line01 = (uint64_t(line0) << 32) | line1;
+    const uint64_t line12 = (uint64_t(line1) << 32) | line2;
+
+    //step 1: extract and load the outputs
+    out0 = std::complex<type>(line0  >> 16 & 0xfff0, line0  >>  4 & 0xfff0);
+    out1 = std::complex<type>(line01 >> 24 & 0xfff0, line1  >> 12 & 0xfff0);
+    out2 = std::complex<type>(line1  >>  0 & 0xfff0, line12 >> 20 & 0xfff0);
+    out3 = std::complex<type>(line2  >>  8 & 0xfff0, line2  <<  4 & 0xfff0);
+}