[clang] [libc++] Add builtin to clear padding bytes (prework for P0528R3) (PR #75371)

[Eli Friedman via cfe-commits]

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@@ -4315,6 +4453,13 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
 
     return RValue::get(Ptr);
   }
+  case Builtin::BI__builtin_clear_padding: {
+    const Expr *Op = E->getArg(0);
+    Value *Address = EmitScalarExpr(Op);
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efriedma-quic wrote:

EmitPointerWithAlignment()?

https://github.com/llvm/llvm-project/pull/75371