Change Details

If we have an icmp->brcond->br sequence where the brcond just branches to the next block jumping over the br, while the br takes the false edge, then we can emit a Bcc conditional branch to the br's target while inverting the condition. This means we can eliminate the br as an unconditional branch and also avoid generating a cset. This also makes the InstructionSelector instances non-const, because we need to be able to communicate to the InstructionSelect pass that certain generic instructions should be deleted. We can't delete these from inside the target specific selector classes because it would invalidate iterators held up the call stack. Therefore, the select() virtual functions are no longer const, but I think this is reasonable. Improves code size on arm64 -O0 on CTMark by 4.3%.

If we have an icmp->brcond->br sequence where the brcond just branches to the next block jumping over the br, while the br takes the false edge, then we can modify the conditional branch to jump to the br's target while inverting the condition of the incoming icmp. This means we can eliminate the br as an unconditional branch to the fallthrough block.

If we have an icmp->brcond->br sequence where the brcond just branches to the the next block jumping over the br, while the br takes the false edge, then we can emit a Bcc conditional branch to the br's target while inverting the condition. This means we can eliminate the br as an unconditional branch and also avoid generating a cset. This also makes the InstructionSelector instances non-const, because we need to be able to communicate to the InstructionSelect pass that certain generic instructions should be deleted. We can't delete these from inside the target specific selector classes because it would invalidate iterators held up the call stack. Therefore,then we can modify the conditional branch to jump to the br's target while inverting the condition of the incoming icmp. the select() virtual functions are no longer const, but I think this is reasonable. Improves code size on arm64 -O0 on CTMark by 4.3%This means we can eliminate the br as an unconditional branch to the fallthrough block.