Emit a proper error message when register allocators run out of registers.

This can't be just an assertion, users can always write impossible inline
assembly. Such an assembly statement should be included in the error message.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131024 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed