agx: Mark the logical ends of blocks

We need to insert parallel copies at the logical end of blocks, before branches.
Add a pseudo instruction signaling that. Cribbed from ACO.

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16268>

src/asahi/compiler/agx_opcodes.py

@@ -252,6 +252,9 @@ op("xor", _, srcs = 2)
 op("and", _, srcs = 2)
 op("or", _, srcs = 2)
 
+# Indicates the logical end of the block, before final branches/control flow
+op("p_logical_end", _, dests = 0, srcs = 0, can_eliminate = False)
+
 op("p_combine", _, srcs = 4)
 op("p_split", _, srcs = 1, dests = 4)
 op("p_extract", _, srcs = 1, imms = [COMPONENT])