Be careful about scheduling nodes above previous calls. It increase usages of

Be careful about scheduling nodes above previous calls. It increase usages of
more callee-saved registers and introduce copies. Only allows it if scheduling
a node above calls would end up lessen register pressure.

Call operands also has added ABI restrictions for register allocation, so be
extra careful with hoisting them above calls.

rdar://9329627

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130245 91177308-0d34-0410-b5e6-96231b3b80d8