-#define TYPE_SIGNED(t) ((t) -1 < 0)
-
-/* Bound on length of the string representing an integer value of type t.
- Subtract one for the sign bit if t is signed;
- 302 / 1000 is log10 (2) rounded up;
- add one for integer division truncation;
- add one more for a minus sign if t is signed. */
+/* Shift A right by B bits portably, by dividing A by 2**B and
+ truncating towards minus infinity. A and B should be free of side
+ effects, and B should be in the range 0 <= B <= INT_BITS - 2, where
+ INT_BITS is the number of useful bits in an int. GNU code can
+ assume that INT_BITS is at least 32.
+
+ ISO C99 says that A >> B is implementation-defined if A < 0. Some
+ implementations (e.g., UNICOS 9.0 on a Cray Y-MP EL) don't shift
+ right in the usual way when A < 0, so SHR falls back on division if
+ ordinary A >> B doesn't seem to be the usual signed shift. */
+#define SHR(a, b) \
+ (-1 >> 1 == -1 \
+ ? (a) >> (b) \
+ : (a) / (1 << (b)) - ((a) % (1 << (b)) < 0))
+
+/* Bound on length of the string representing an integer type or expression T.
+ Subtract 1 for the sign bit if t is signed; log10 (2.0) < 146/485;
+ add 1 for integer division truncation; add 1 more for a minus sign
+ if needed. */