Adding TODO.

TODO.md

@@ -0,0 +1,60 @@
+
+## Instructions
+
+```
+stbu
+lwzu
+
+addx
+addix
+addic
+addzex
+subfx
+subfex
+subficx
+
+mulli
+mullwx
+divwux
+
+andix
+orx
+
+rlwinmx
+rldiclx
+extsbx
+slwx
+srawix
+
+# can be no-op
+dcbt
+dcbtst
+
+twi
+
+```
+
+## Codegen
+
+### Indirect branches (ctr/lr)
+
+emit_control.cc XeEmitBranchTo
+Need to take the value in LR/CTR and do something with it.
+
+Fast path:
+- Every time LR would be stashed, add the value of LR (some NIA) to a lookup
+  table.
+- When doing an indirect branch first lookup the address in the table.
+- If not found, slow path, else jump.
+
+Slow path:
+- Call out and do an SDB lookup.
+- If found, return, add to lookup table, and jump.
+- If not found, need new function codegen!
+
+### Caching of register values in basic blocks
+
+Right now the SSA values seem to leak from the blocks somehow. All caching
+is disabled.
+
+```