Reapply "Verifier: Check for incompatible bit piece expressions"

This reverts commit r234717, reapplying r234698 (in spirit).

As described in r234717, the original `Verifier` check had a
use-after-free.  Instead of storing pointers to "interesting" debug info
intrinsics whose bit piece expressions should be verified once we have
typerefs, do a second traversal.  I've added a testcase to catch the
`llc` crasher.

Original commit message:

    Verifier: Check for incompatible bit piece expressions

    Convert an assertion into a `Verifier` check.  Bit piece expressions
    must fit inside the variable, and mustn't be the entire variable.
    Catching this in the verifier will help us find bugs sooner, and makes
    `DIVariable::getSizeInBits()` dead code.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@234776 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -1535,15 +1535,7 @@ void DebugLocEntry::finalize(const AsmPrinter &AP,
         Offset += PieceOffset-Offset;
       }
       Offset += PieceSize;
-   
-#ifndef NDEBUG
-      DIVariable Var = Piece.getVariable();
-      unsigned VarSize = Var.getSizeInBits(TypeIdentifierMap);
-      assert(PieceSize+PieceOffset <= VarSize
-             && "piece is larger than or outside of variable");
-      assert(PieceSize != VarSize
-             && "piece covers entire variable");
-#endif
+
       emitDebugLocValue(AP, TypeIdentifierMap, Streamer, Piece, PieceOffset);
     }
   } else {