LSB of each element in the result vector
Note that element width overrides are respected on the INT src or destination register (but that elwidth overrides on CRs are meaningless)
+
+# v3.1 setbc instructions
+
+there are additional setb conditional instructions in v3.1 (p129)
+
+ RT = (CR[BI] == 1) ? 1 : 0
+
+which also negate that, and also return -1 / 0. these are similar yo crweird but not the same purpose.
+
+