[clang][bytecode] Refine diagnostics for volatile reads (#136857)

Differentiate between a volarile read via a lvalue-to-rvalue cast of a
volatile qualified subexpression and a read from a pointer with a
volatile base object.

1 files changed, 24 insertions, 5 deletions

diff --git a/clang/lib/AST/ByteCode/Interp.cpp b/clang/lib/AST/ByteCode/Interp.cpp
index b755a07..6f277a7 100644
--- a/clang/lib/AST/ByteCode/Interp.cpp
+++ b/clang/lib/AST/ByteCode/Interp.cpp
@@ -641,11 +641,30 @@ static bool CheckVolatile(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
   if (!PtrType.isVolatileQualified())
     return true;
 
-  const SourceInfo &Loc = S.Current->getSource(OpPC);
-  if (S.getLangOpts().CPlusPlus)
-    S.FFDiag(Loc, diag::note_constexpr_access_volatile_type) << AK << PtrType;
-  else
-    S.FFDiag(Loc);
+  if (!S.getLangOpts().CPlusPlus)
+    return Invalid(S, OpPC);
+
+  const NamedDecl *ND = nullptr;
+  int DiagKind;
+  SourceLocation Loc;
+  if (const auto *F = Ptr.getField()) {
+    DiagKind = 2;
+    Loc = F->getLocation();
+    ND = F;
+  } else if (auto *VD = Ptr.getFieldDesc()->asValueDecl()) {
+    DiagKind = 1;
+    Loc = VD->getLocation();
+    ND = VD;
+  } else {
+    DiagKind = 0;
+    if (const auto *E = Ptr.getFieldDesc()->asExpr())
+      Loc = E->getExprLoc();
+  }
+
+  S.FFDiag(S.Current->getLocation(OpPC),
+           diag::note_constexpr_access_volatile_obj, 1)
+      << AK << DiagKind << ND;
+  S.Note(Loc, diag::note_constexpr_volatile_here) << DiagKind;
   return false;
 }