Add a few Subzero intrinsics (not the atomic ones yet).

crosstest/mem_intrin_main.c

+/* crosstest.py --test=mem_intrin.c --driver=mem_intrin_main.c \
+   --prefix=Subzero_ --output=mem_intrin */
+
+#include <stdint.h>
+#include <stdio.h>
+
+int memcpy_test(uint8_t n);
+int memmove_test(uint8_t n);
+int memset_test(uint8_t n);
+int Subzero_memcpy_test(uint8_t n);
+int Subzero_memmove_test(uint8_t n);
+int Subzero_memset_test(uint8_t n);
+
+int main(int argc, char **argv) {
+  unsigned TotalTests = 0;
+  unsigned Passes = 0;
+  unsigned Failures = 0;
+#define do_test(test_func) \
+  for (uint8_t i = 0; i < 100; ++i) { \
+    ++TotalTests; \
+    int llc_result = test_func(i); \
+    int sz_result = Subzero_##test_func(i); \
+    if (llc_result == sz_result) { \
+      ++Passes; \
+    } else { \
+      ++Failures; \
+      printf("Failure (%s): i=%d, llc=%d, sz=%d\n", #test_func, \
+             i, llc_result, sz_result); \
+    } \
+  }
+
+  do_test(memcpy_test)
+  do_test(memmove_test)
+  /* Broken: invalid push byte for val argument */
+  /* do_test(memset_test) */
+  printf("TotalTests=%u Passes=%u Failures=%u\n", TotalTests, Passes, Failures);
+  return Failures;
+}