[DebugInfo] Verifier for DILabel.

[probinson]

This wants to have a test, which probably means it should be combined with one or more of the other patches that support creating/parsing the label metadata.

[HsiangKai]

In D45089#1053390, @probinson wrote:

This wants to have a test, which probably means it should be combined with one or more of the other patches that support creating/parsing the label metadata.

Merged into D45024, this patch should be abandoned.

lib/IR/Verifier.cpp

void Verifier::visitDILocalVariable(const DILocalVariable &N) {
   visitDIVariable(N);
 
   AssertDI(isType(N.getRawType()), "invalid type ref", &N, N.getRawType());
   AssertDI(N.getTag() == dwarf::DW_TAG_variable, "invalid tag", &N);
   AssertDI(N.getRawScope() && isa<DILocalScope>(N.getRawScope()),
            "local variable requires a valid scope", &N, N.getRawScope());
 }
 
+void Verifier::visitDILabel(const DILabel &N) {
+  if (auto *S = N.getRawScope())
+    AssertDI(isa<DIScope>(S), "invalid scope", &N, S);
+  if (auto *F = N.getRawFile())
+    AssertDI(isa<DIFile>(F), "invalid file", &N, F);
+
+  AssertDI(N.getTag() == dwarf::DW_TAG_label, "invalid tag", &N);
+  AssertDI(N.getRawScope() && isa<DILocalScope>(N.getRawScope()),
+           "label requires a valid scope", &N, N.getRawScope());
+}
+
 void Verifier::visitDIExpression(const DIExpression &N) {
   AssertDI(N.isValid(), "invalid expression", &N);
 }
 
 void Verifier::visitDIGlobalVariableExpression(
     const DIGlobalVariableExpression &GVE) {
   AssertDI(GVE.getVariable(), "missing variable");
   if (auto *Var = GVE.getVariable())