Remove documentation for a deleted pass.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206097 91177308-0d34-0410-b5e6-96231b3b80d8
Use dwarf::Tag rather than unsigned for DIE::Tag to make debugging easier.

Nice to be able to just print out the Tag and have the debugger print
dwarf::DW_TAG_subprogram or whatever, rather than an int.

It's a bit finicky (for example DIDescriptor::getTag still returns
unsigned) because some places still handle real dwarf tags + our fake
tags (one day we'll remove the fake tags, hopefully).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206098 91177308-0d34-0410-b5e6-96231b3b80d8
[ARM64] Fix the cost model for cheap large constants.

Originally the cost model would give up for large constants and just return the
maximum cost. This is not what we want for constant hoisting, because some of
these constants are large in bitwidth, but are still cheap to materialize.

This commit fixes the cost model to either return TCC_Free if the cost cannot be
determined, or accurately calculate the cost even for large constants
(bitwidth > 128).

This fixes <rdar://problem/16591573>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206100 91177308-0d34-0410-b5e6-96231b3b80d8