* <http://lists.libre-soc.org/pipermail/libre-soc-dev/2021-August/003416.html>
TODO
+| 0-1 | 2 | 3 4 | description |
+| --- | --- |---------|-------------------------- |
+| 00 | 0 | ALL sz | normal mode |
+| 01 | VLI | ALL sz | VLSET mode |
+
+Fields:
+
+* **sz** if predication is enabled will put zeros into the src CR when the predicate bit is zero. otherwise the element is ignored or skipped, depending on context.
+* **ALL** when set, all branch conditional tests must pass in order for
+the branch to succeed.
+* **VLI** In VLSET mode, VL is set equal (truncated) to the first branch
+which succeeds. If VLI (Vector Length Inclusive) is clear, VL is truncated
+to *exclude* the current element, otherwise it is included.