MI-Sched: Adjust regpressure limits for reserved regs.
MI-Sched: cleanup DEBUG output.
Fix IMULX machine model. Multiple def operands require multiple SchedWrites.
Make rematerialization in the coalescer less sensitive to LRG order.
Modify the -join-globalcopies option (off by default).

Always coalesce in forward order to propagate rematerialization.
I'm fixing this option so I can enable it by default soon.
Fix a -join-globalcopies bug; handle undef operands.
whitespace
Refactor LiveRangeEdit::eliminateDeadDefs.

I want to add logic to handle more cases.
Handle more cases in LiveRangeEdit::eliminateDeadDefs.

Live intervals for dead physregs may be created during coalescing. We
need to update these in the event that their instruction goes away.

crash.ll is the unit test that catches it when MI sched is enabled on
X86.
Added -precompute-phys-liveness for testing LiveIntervals updates.
Update physreg live intervals during remat.