Fix target-customized spilling in the register scavenger
Fix target-customized spilling in the register scavenger

This is a follow-up to r178073 (which should actually make target-customized
spilling work again).

I still don't have a regression test for this (but it would be good to have
one; Thumb 1 and Mips16 use this callback as well).

Patch by Richard Sandiford.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@178137 91177308-0d34-0410-b5e6-96231b3b80d8

chubbymaggie/asap,dslab-epfl/asap,chubbymaggie/asap,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,chubbymaggie/asap,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,chubbymaggie/asap,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,apple/swift-llvm,llvm-mirror/llvm,chubbymaggie/asap,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,llvm-mirror/llvm,GPUOpen-Drivers/llvm,dslab-epfl/asap,llvm-mirror/llvm,chubbymaggie/asap,dslab-epfl/asap,dslab-epfl/asap,apple/swift-llvm,apple/swift-llvm