Add a backend function for creating symbolic values representing larg…

…e integers (#155)

* add _sym_build_integer_arbitrary_length function
* simplify _sym_build_integer_from_buffer function

runtime/RuntimeCommon.h

@@ -51,6 +51,7 @@ void _sym_initialize(void);
  */
 SymExpr _sym_build_integer(uint64_t value, uint8_t bits);
 SymExpr _sym_build_integer128(uint64_t high, uint64_t low);
+SymExpr _sym_build_integer_from_buffer(void *buffer, unsigned num_bits);
 SymExpr _sym_build_float(double value, int is_double);
 SymExpr _sym_build_null_pointer(void);
 SymExpr _sym_build_true(void);

runtime/qsym_backend/Runtime.cpp

@@ -215,6 +215,12 @@ SymExpr _sym_build_integer128(uint64_t high, uint64_t low) {
   return registerExpression(g_expr_builder->createConstant({128, words}, 128));
 }
 
+SymExpr _sym_build_integer_from_buffer(void *buffer, unsigned num_bits) {
+  assert(num_bits % 64 == 0);
+  return registerExpression(g_expr_builder->createConstant(
+      {num_bits, num_bits / 64, (uint64_t *)buffer}, num_bits));
+}
+
 SymExpr _sym_build_null_pointer() {
   return registerExpression(
       g_expr_builder->createConstant(0, sizeof(uintptr_t) * 8));