Planning to add support for named vregs. This puts is in a conundrum since
physregs are named as well. To rectify this we need to use a sigil other than
'%' for physregs in MIR. We've settled on using '$' for physregs but first we
must repurpose it from external symbols using it, which is what this commit is
all about. We think '&' will have familiar semantics for C/C++ users.
llvm-svn: 322146
CodeGen uses MO_ExternalSymbol to represent the inline assembly strings.
Empty strings for symbol names appear to be invalid. For now just
special case the output code to avoid hitting an `assert()` in
`printLLVMNameWithoutPrefix()`.
This fixes https://llvm.org/PR33317
llvm-svn: 304815
Puyan Lotfi