IR: Take advantage of -verify checks for MDExpression

Now that we check `MDExpression` during `-verify` (r232299), make
the `DIExpression` wrapper more strict:

  - remove redundant checks in `DebugInfoVerifier`,
  - overload `get()` to `cast_or_null<MDExpression>` (superseding
    `getRaw()`),
  - stop checking for null in any accessor, and
  - remove `DIExpression::Verify()` entirely in favour of
    `MDExpression::isValid()`.

There is still some logic in this class, mostly to do with high-level
iterators; I'll defer cleaning up those until the rest of the wrappers
are similarly strict.

llvm-svn: 232412

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
index 6e462bf06d0..952da04a4b4 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -88,7 +88,8 @@ public:
     : Var(V), Expr(1, E), TheDIE(nullptr), DotDebugLocOffset(~0U),
       MInsn(nullptr), DD(DD) {
     FrameIndex.push_back(FI);
-    assert(Var.Verify() && E.Verify());
+    assert(Var.Verify());
+    assert(!E || E->isValid());
   }
 
   /// Construct a DbgVariable from a DEBUG_VALUE.