instruction to avoid a copy AFTER the 2-addr instruction. The 2-addr pass
currently only commutes to avoid inserting a copy BEFORE the two addr instr.
+===-------------------------------------------------------------------------===
+
+Compile offsets from allocas:
+
+int *%test() {
+ %X = alloca { int, int }
+ %Y = getelementptr {int,int}* %X, int 0, uint 1
+ ret int* %Y
+}
+
+into a single add, not two:
+
+_test:
+ addi r2, r1, -8
+ addi r3, r2, 4
+ blr
+
+--> important for C++.
+