[clang] [clang] Allow builtin addc/subc to be constant evaluated (PR #81656)

[Thorsten Schütt via cfe-commits]

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@@ -12696,6 +12696,56 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
     return BuiltinOp == Builtin::BI__atomic_always_lock_free ?
         Success(0, E) : Error(E);
   }
+  case Builtin::BI__builtin_addcb:
+  case Builtin::BI__builtin_addcs:
+  case Builtin::BI__builtin_addc:
+  case Builtin::BI__builtin_addcl:
+  case Builtin::BI__builtin_addcll:
+  case Builtin::BI__builtin_subcb:
+  case Builtin::BI__builtin_subcs:
+  case Builtin::BI__builtin_subc:
+  case Builtin::BI__builtin_subcl:
+  case Builtin::BI__builtin_subcll: {
+    LValue CarryOutLValue;
+    APSInt LHS, RHS, CarryIn, Result;
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tschuett wrote:

If you search the internet for `llvm APSInt`, you will find the `S` means signed. You will also find `llvm APInt`. The latter is the unsigned version.

https://github.com/llvm/llvm-project/pull/81656