[compiler] support 128-bit bitfields (#500)

* support setting and accessing fields of a 128-bit bitfield

* remove print

* rework static constants

* support 128-bit bitfields as part of static structures

* dynamic construction

common/util/BitUtils.cpp

@@ -0,0 +1,37 @@
+#include "BitUtils.h"
+
+#include <cstring>
+
+bool integer_fits(s64 in, int size, bool is_signed) {
+  switch (size) {
+    case 1:
+      if (is_signed) {
+        return in >= INT8_MIN && in <= INT8_MAX;
+      } else {
+        return in >= 0 && in <= UINT8_MAX;
+      }
+    case 2:
+      if (is_signed) {
+        return in >= INT16_MIN && in <= INT16_MAX;
+      } else {
+        return in >= 0 && in <= UINT16_MAX;
+      }
+    case 4:
+      if (is_signed) {
+        return in >= INT32_MIN && in <= INT32_MAX;
+      } else {
+        return in >= 0 && in <= UINT32_MAX;
+      }
+    case 8:
+      return true;
+    default:
+      assert(false);
+      return false;
+  }
+}
+
+u32 float_as_u32(float x) {
+  u32 result;
+  memcpy(&result, &x, 4);
+  return result;
+}