CodeGen: Use MachineInstr& in RegAllocFast, NFC
CodeGen: Use MachineInstr& in RegAllocFast, NFC

Use MachineInstr& instead of MachineInstr* in RegAllocFast to avoid
implicit conversions from MachineInstrBundleIterator.  RAFast::spillAll
and RAFast::spillVirtReg still take iterators, since their argument may
be an end iterator from MachineBasicBlock::getFirstTerminator.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@274353 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm