dev-arm: Add a GICv3 model

Change-Id: Ib0067fc743f84ff7be9f12d2fc33ddf63736bdd1
Reviewed-on: https://gem5-review.googlesource.com/c/13436
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>

src/base/bitfield.hh

@@ -282,4 +282,15 @@ inline uint64_t alignToPowerOfTwo(uint64_t val)
     return val;
 };
 
+/**
+ * Count trailing zeros in a 32-bit value.
+ *
+ * Returns 32 if the value is zero. Note that the GCC builtin is
+ * undefined if the value is zero.
+ */
+inline int ctz32(uint32_t value)
+{
+    return value ? __builtin_ctz(value) : 32;
+}
+
 #endif // __BASE_BITFIELD_HH__