Begin the loop identification process with the data structures and fundamental methods of back edge discovery.

Expand IDIOM 3 to include subtraction of small immediate from condition code; add IDIOM 13 for all NEGATEDPTR references; increase MEDS propagation of POINTER types.

Build RTLs for dryrun lib opcodes; fix uninit vars and clean up code; start mul by large const idiom recognition.

Do not allow DEF signedness to become mixed due to propagation of USE operand signedness within an RTL.

Fix FindOutgoingArgsSize() for cases with stack entries below the main allocation point; suppress signedness annotations on partial stores that do not overwrite the sign bit.