bitops.h: Implement half-shuffle and half-unshuffle ops

A half-shuffle operation takes a word with zeros in the high half:
 0000 0000 0000 0000 ABCD EFGH IJKL MNOP
and spreads the bits out so they are in every other bit of the word:
 0A0B 0C0D 0E0F 0G0H 0I0J 0K0L 0M0N 0O0P
A half-unshuffle performs the reverse operation.

Provide functions in bitops.h which implement these operations
for 32-bit and 64-bit inputs, and add tests for them.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Shannon Zhao <shannon.zhao@linaro.org>
Tested-by: Shannon Zhao <shannon.zhao@linaro.org>
Message-id: 1465915112-29272-3-git-send-email-peter.maydell@linaro.org

1 files changed, 72 insertions, 0 deletions

diff --git a/tests/test-bitops.c b/tests/test-bitops.c
index eb19a36..5a791d2 100644
--- a/tests/test-bitops.c
+++ b/tests/test-bitops.c
@@ -65,10 +65,82 @@ static void test_sextract64(void)
     }
 }
 
+typedef struct {
+    uint32_t unshuffled;
+    uint32_t shuffled;
+} Shuffle32Test;
+
+typedef struct {
+    uint64_t unshuffled;
+    uint64_t shuffled;
+} Shuffle64Test;
+
+static const Shuffle32Test test_shuffle32_data[] = {
+    { 0x0000FFFF, 0x55555555 },
+    { 0x000081C5, 0x40015011 },
+};
+
+static const Shuffle64Test test_shuffle64_data[] = {
+    { 0x00000000FFFFFFFFULL, 0x5555555555555555ULL },
+    { 0x00000000493AB02CULL, 0x1041054445000450ULL },
+};
+
+static void test_half_shuffle32(void)
+{
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(test_shuffle32_data); i++) {
+        const Shuffle32Test *test = &test_shuffle32_data[i];
+        uint32_t r = half_shuffle32(test->unshuffled);
+
+        g_assert_cmpint(r, ==, test->shuffled);
+    }
+}
+
+static void test_half_shuffle64(void)
+{
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(test_shuffle64_data); i++) {
+        const Shuffle64Test *test = &test_shuffle64_data[i];
+        uint64_t r = half_shuffle64(test->unshuffled);
+
+        g_assert_cmpint(r, ==, test->shuffled);
+    }
+}
+
+static void test_half_unshuffle32(void)
+{
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(test_shuffle32_data); i++) {
+        const Shuffle32Test *test = &test_shuffle32_data[i];
+        uint32_t r = half_unshuffle32(test->shuffled);
+
+        g_assert_cmpint(r, ==, test->unshuffled);
+    }
+}
+
+static void test_half_unshuffle64(void)
+{
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(test_shuffle64_data); i++) {
+        const Shuffle64Test *test = &test_shuffle64_data[i];
+        uint64_t r = half_unshuffle64(test->shuffled);
+
+        g_assert_cmpint(r, ==, test->unshuffled);
+    }
+}
+
 int main(int argc, char **argv)
 {
     g_test_init(&argc, &argv, NULL);
     g_test_add_func("/bitops/sextract32", test_sextract32);
     g_test_add_func("/bitops/sextract64", test_sextract64);
+    g_test_add_func("/bitops/half_shuffle32", test_half_shuffle32);
+    g_test_add_func("/bitops/half_shuffle64", test_half_shuffle64);
+    g_test_add_func("/bitops/half_unshuffle32", test_half_unshuffle32);
+    g_test_add_func("/bitops/half_unshuffle64", test_half_unshuffle64);
     return g_test_run();
 }