[clang] [clang] Add support for relaxed constexpr evaluation to interpreter (PR #217311)

[Timm Baeder via cfe-commits]

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@@ -2713,9 +2715,13 @@ bool InvalidShuffleVectorIndex(InterpState &S, CodePtr OpPC, uint32_t Index) {
 bool CheckPointerToIntegralCast(InterpState &S, CodePtr OpPC,
                                 const Pointer &Ptr, unsigned BitWidth) {
   SourceInfo E = S.Current->getSource(OpPC);
-  S.CCEDiag(E, diag::note_constexpr_invalid_cast)
-      << 2 << S.getLangOpts().CPlusPlus << S.Current->getRange(OpPC);
 
+  S.CCEDiag(E, diag::note_constexpr_invalid_cast_ptrtoint)
+      << diag::ConstexprInvalidCastKind::ThisConversionOrReinterpret
+      << S.getLangOpts().CPlusPlus << S.Current->getRange(OpPC);
+  APValue V = Ptr.toAPValue(S.getASTContext());
+  if (V.getLValueBase())
+    S.CCEDiag(E, diag::note_constexpr_has_lvalue) << S.Current->getRange(OpPC);
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tbaederr wrote:

What does the lvaluebase check do? Is this different than `Ptr.isZero()`?

https://github.com/llvm/llvm-project/pull/217311