Try schedule def + use closer whne Sethi-Ullman numbers are the same.

Try schedule def + use closer whne Sethi-Ullman numbers are the same.
e.g.
t1 = op t2, c1
t3 = op t4, c2
and the following instructions are both ready.
t2 = op c3
t4 = op c4

Then schedule t2 = op first.
i.e.
t4 = op c4
t2 = op c3
t1 = op t2, c1
t3 = op t4, c2

This creates more short live intervals which work better with the register
allocator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@35089 91177308-0d34-0410-b5e6-96231b3b80d8