[debuginfo] generate debug info with asm+.file

Summary:
For assembly input files, generate debug info even when the .file
directive is present, provided it does not include a file-number
argument.  Fixes PR38695.

Reviewers: probinson, sidneym

Subscribers: aprantl, hiraditya, JDevlieghere, llvm-commits

Differential Revision: https://reviews.llvm.org/D51315



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@340839 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed