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, 123 insertions, 0 deletions

diff --git a/host/lib/convert/convert_pack_sc12.hpp b/host/lib/convert/convert_pack_sc12.hpp
new file mode 100644
index 000000000..754c47cd2
--- /dev/null
+++ b/host/lib/convert/convert_pack_sc12.hpp
@@ -0,0 +1,123 @@
+//
+// 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 (*towire32_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;
+};
+
+enum item32_sc12_3x_enable {
+    CONVERT12_LINE0 = 0x01,
+    CONVERT12_LINE1 = 0x02,
+    CONVERT12_LINE2 = 0x04,
+    CONVERT12_LINE_ALL = 0x07,
+};
+
+/*
+ * Packed 12-bit converter with selective line enable
+ *
+ * The converter operates on 4 complex inputs and selectively writes to one to
+ * three 32-bit lines. Line selection allows for partial writes of less than
+ * 4 complex samples, or a full 3 x 32-bit struct. Writes are always full 32-bit
+ * lines, so in the case of partial writes, the number of bytes written will
+ * exceed the the number of bytes filled by actual samples.
+ *
+ *  _ _ _ _ _ _ _ _
+ * |_ _ _1_ _ _|_ _| 0
+ * |_2_ _ _|_ _ _3_|
+ * |_ _|_ _ _4_ _ _| 2
+ * 31              0
+ */
+template <towire32_type towire>
+void pack(item32_sc12_3x &output, int enable, const int32_t iq[8])
+{
+    if (enable & CONVERT12_LINE0)
+        output.line0 = towire(iq[0] << 20 | iq[1] <<  8 | iq[2] >> 4);
+    if (enable & CONVERT12_LINE1)
+        output.line1 = towire(iq[2] << 28 | iq[3] << 16 | iq[4] << 4 | iq[5] >> 8);
+    if (enable & CONVERT12_LINE2)
+        output.line2 = towire(iq[5] << 24 | iq[6] << 12 | iq[7] << 0);
+}
+
+template <typename type, towire32_type towire>
+void convert_star_4_to_sc12_item32_3
+(
+    const std::complex<type> &in0,
+    const std::complex<type> &in1,
+    const std::complex<type> &in2,
+    const std::complex<type> &in3,
+    const int enable,
+    item32_sc12_3x &output,
+    const double scalar,
+    typename std::enable_if<std::is_floating_point<type>::value>::type* = NULL
+)
+{
+    int32_t iq[8] {
+        int32_t(in0.real()*scalar) & 0xfff,
+        int32_t(in0.imag()*scalar) & 0xfff,
+        int32_t(in1.real()*scalar) & 0xfff,
+        int32_t(in1.imag()*scalar) & 0xfff,
+
+        int32_t(in2.real()*scalar) & 0xfff,
+        int32_t(in2.imag()*scalar) & 0xfff,
+        int32_t(in3.real()*scalar) & 0xfff,
+        int32_t(in3.imag()*scalar) & 0xfff,
+    };
+    pack<towire>(output, enable, iq);
+}
+
+template <typename type, towire32_type towire>
+void convert_star_4_to_sc12_item32_3
+(
+    const std::complex<type> &in0,
+    const std::complex<type> &in1,
+    const std::complex<type> &in2,
+    const std::complex<type> &in3,
+    const int enable,
+    item32_sc12_3x &output,
+    const double,
+    typename std::enable_if<std::is_same<type, short>::value>::type* = NULL
+)
+{
+    int32_t iq[8] {
+        int32_t(in0.real() >> 4) & 0xfff,
+        int32_t(in0.imag() >> 4) & 0xfff,
+        int32_t(in1.real() >> 4) & 0xfff,
+        int32_t(in1.imag() >> 4) & 0xfff,
+
+        int32_t(in2.real() >> 4) & 0xfff,
+        int32_t(in2.imag() >> 4) & 0xfff,
+        int32_t(in3.real() >> 4) & 0xfff,
+        int32_t(in3.imag() >> 4) & 0xfff,
+    };
+    pack<towire>(output, enable, iq);
+}