Deal with branchy instructions

[alyssarosenzweig]

We'd like to move towards an IR with purely local liveness. This requires reworking the dispatcher for any opcode that translates to multiple blocks. This ticket tracks the audit of all such opcodes.

These opcodes need logic changes:

• daa (rewrite Demon Addition Adjust (DAA) and other demonic opcodes #3514 )
• das (rewrite Demon Addition Adjust (DAA) and other demonic opcodes #3514 )
• aaa (rewrite Demon Addition Adjust (DAA) and other demonic opcodes #3514 )
• aad (rewrite Demon Addition Adjust (DAA) and other demonic opcodes #3514 )
• rep cmps (Eliminate xblock liveness with rep cmp/lod/scas #3542)
• rep lods (Eliminate xblock liveness with rep cmp/lod/scas #3542)
• rep scas (Eliminate xblock liveness with rep cmp/lod/scas #3542)
• cmpxchg pair (OpcodeDispatcher: eliminate branch in cmpxchg pair #3522 )
• shift left (Eliminate xblock liveness for shifts #3548)
• shift right (Eliminate xblock liveness for shifts #3548)
• signed shift left (Eliminate xblock liveness for shifts #3548)
• rotate right (rewrite ROL/ROR #3539)
• rotate left (rewrite ROL/ROR #3539 )
• rcr (OpcodeDispatcher: eliminate xblock liveness for rcl/rcr #3536)
• rcr smaller (OpcodeDispatcher: eliminate xblock liveness for rcl/rcr #3536)
• rcl (OpcodeDispatcher: eliminate xblock liveness for rcl/rcr #3536)
• rcl smaller (OpcodeDispatcher: eliminate xblock liveness for rcl/rcr #3536)
• XSave (Eliminate crossblock liveness in xsave/xrstor #3528 )
• XRstor (Eliminate crossblock liveness in xsave/xrstor #3528 )
• self modifying code (Validate that we have no crossblock liveness #3550)

These I've audited to be ok

• int
• jumps
• undefined