Partial merge of r293110 into the 4.0 branch
Partial merge of r293110 into the 4.0 branch

Avoid printing optimization remarks from llc unless they are enabled.

Fixes http://llvm.org/PR32184

git-svn-id: 27e84c199cfb3049f109a3001c965f4b97b0bded@299409 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm