DebugInfo: Remove special iterators from DIExpression

Remove special iterators from `DIExpression` in favour of same in
`MDExpression`.  There should be no functionality change here.

Note that the APIs are slightly different: `getArg(unsigned)` counts
from 0, not 1, in the `MDExpression` version of the iterator.

llvm-svn: 234285
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
index 57fd8ab..0e15f35 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -523,7 +523,7 @@
     assert(Expr != DV.getExpression().end() &&
            "Wrong number of expressions");
     DwarfExpr.AddMachineRegIndirect(FrameReg, Offset);
-    DwarfExpr.AddExpression(Expr->begin(), Expr->end());
+    DwarfExpr.AddExpression((*Expr)->expr_op_begin(), (*Expr)->expr_op_end());
     ++Expr;
   }
   addBlock(*VariableDie, dwarf::DW_AT_location, Loc);
@@ -773,7 +773,7 @@
     ValidReg = DwarfExpr.AddMachineRegIndirect(Location.getReg(),
                                                Location.getOffset());
     if (ValidReg)
-      DwarfExpr.AddExpression(Expr.begin(), Expr.end());
+      DwarfExpr.AddExpression(Expr->expr_op_begin(), Expr->expr_op_end());
   } else
     ValidReg = DwarfExpr.AddMachineRegExpression(Expr, Location.getReg());