Auto merge of rust-lang#101483 - oli-obk:guaranteed_opt, r=fee1-dead

The `<*const T>::guaranteed_*` methods now return an option for the unknown case

cc rust-lang#53020 (comment)

I chose `0` for "not equal" and `1` for "equal" and left `2` for the unknown case so backends can just forward to raw pointer equality and it works ✨

r? `@fee1-dead` or `@lcnr`

cc `@rust-lang/wg-const-eval`

src/intrinsics/mod.rs

@@ -816,20 +816,13 @@ fn codegen_regular_intrinsic_call<'tcx>(
             ret.write_cvalue(fx, val);
         }
 
-        sym::ptr_guaranteed_eq => {
+        sym::ptr_guaranteed_cmp => {
             intrinsic_args!(fx, args => (a, b); intrinsic);
 
             let val = crate::num::codegen_ptr_binop(fx, BinOp::Eq, a, b);
             ret.write_cvalue(fx, val);
         }
 
-        sym::ptr_guaranteed_ne => {
-            intrinsic_args!(fx, args => (a, b); intrinsic);
-
-            let val = crate::num::codegen_ptr_binop(fx, BinOp::Ne, a, b);
-            ret.write_cvalue(fx, val);
-        }
-
         sym::caller_location => {
             intrinsic_args!(fx, args => (); intrinsic);