Label targets are not represented correctly for llvm-as consumption

[kquick]

Bitcode generated by clang and then parsed via llvm-pretty-bc-parser and then output via this library into .ll files may not be usable with llvm-as because of the representation of the label targets.

Generated code contains call void @llvm.db.label(metadata !DILabel(scope: !8, name: loop, which fails on loop (presumably because it needs to be quoted).

This error can be seen running `cabal run disasm-test -- -p '/callbr.c/' (requires https://github.com/galoisinc/llvm-pretty-bc-parser/pulls/230).

[kquick]

[From Ryan Scott:]

OK, I've extracted a test case that confirms that this is in fact an llvm-pretty pretty-printer issue:

// callbr.c
int main(void) {
  int cond = 0;
  asm volatile goto("testl %0, %0; jne %l1;"
                    : /* No outputs */
                    : "r"(cond)
                    : /* No clobbers */
                    : label_true, loop);
  return 0;
loop:
  return 0;
label_true:
  return 1;
}

First, note how LLVM itself formats DILabels:

$ clang -S -emit-llvm -g -O0 callbr.c -o callbr.ll
$ cat callbr.ll | grep "DILabel"
!17 = !DILabel(scope: !7, name: "loop", file: !1, line: 14)
!20 = !DILabel(scope: !7, name: "label_true", file: !1, line: 16)

Now note how it appears after round-tripping through llvm-pretty:

-- Main.hs
module Main (main) where

import Data.LLVM.BitCode
import Text.LLVM.PP

main :: IO ()
main = do
  res <- parseBitCodeFromFile "callbr.bc"
  case res of
    Left err -> fail $ formatError err
    Right bc -> print $ ppLLVM38 ppModule bc

Running this program after compiling with clang -c -emit-llvm -g -O0 callbr.c -o callbr.bc gives:

  call void @llvm.dbg.label(metadata !DILabel(scope: !7, name: loop,
  ...
  call void @llvm.dbg.label(metadata !DILabel(scope: !7,
                                              name: label_true,

Which lacks double quotes around the name values.

[RyanGlScott]

I've opened #115, which I believe should address this. Can you give it a try, @kquick?

[kquick]

This does seem to fix those issues (in conjunction with the llvm-pretty-bc-parser adaptation on GaloisInc/llvm-pretty-bc-parser#233), but runs into another one: #116