[clang] [llvm] [AArch64][PAC] Sign block addresses used in indirectbr. (PR #97647)

[Eli Friedman via cfe-commits]

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@@ -10909,6 +10909,14 @@ QualType Sema::CheckAdditionOperands(ExprResult &LHS, ExprResult &RHS,
   if (isObjCPointer && checkArithmeticOnObjCPointer(*this, Loc, PExp))
     return QualType();
 
+  // Arithmetic on label addresses is normally allowed, except when we add
+  // a ptrauth signature to the addresses.
+  if (isa<AddrLabelExpr>(PExp) && getLangOpts().PointerAuthIndirectGotos) {
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efriedma-quic wrote:

I don't think this catches all the relevant cases: there are various ways you could "hide" an address-of-label from this check.  Parentheses, a conditional operator, a constexpr variable, etc.

Maybe the check should be in IntExprEvaluator::VisitBinaryOperator.

https://github.com/llvm/llvm-project/pull/97647