miri: fix offset_from behavior on wildcard pointers

Author: RalfJung

tests/fail/intrinsics/ptr_offset_from_different_ints.rs

@@ -16,6 +16,6 @@ fn main() {
         let _ = p1.byte_offset_from(p1);
 
         // UB because different pointers.
-        let _ = p1.byte_offset_from(p2); //~ERROR: different pointers without provenance
+        let _ = p1.byte_offset_from(p2); //~ERROR: no provenance
     }
 }

tests/fail/intrinsics/ptr_offset_from_different_ints.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: `ptr_offset_from` called on different pointers without provenance (i.e., without an associated allocation)
+error: Undefined Behavior: out-of-bounds `offset_from`: 0xa[noalloc] is a dangling pointer (it has no provenance)
   --> $DIR/ptr_offset_from_different_ints.rs:LL:CC
    |
 LL |         let _ = p1.byte_offset_from(p2);
-   |                 ^^^^^^^^^^^^^^^^^^^^^^^ `ptr_offset_from` called on different pointers without provenance (i.e., without an associated allocation)
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^ out-of-bounds `offset_from`: 0xa[noalloc] is a dangling pointer (it has no provenance)
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information

tests/fail/intrinsics/ptr_offset_from_unsigned_neg.rs

@@ -1,8 +1,9 @@
+//@normalize-stderr-test: "\d+ < \d+" -> "$$ADDR < $$ADDR"
 #![feature(ptr_sub_ptr)]
 
 fn main() {
     let arr = [0u8; 8];
     let ptr1 = arr.as_ptr();
     let ptr2 = ptr1.wrapping_add(4);
-    let _val = unsafe { ptr1.sub_ptr(ptr2) }; //~ERROR: first pointer has smaller offset than second: 0 < 4
+    let _val = unsafe { ptr1.sub_ptr(ptr2) }; //~ERROR: first pointer has smaller address than second
 }

tests/fail/intrinsics/ptr_offset_from_unsigned_neg.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: `ptr_offset_from_unsigned` called when first pointer has smaller offset than second: 0 < 4
+error: Undefined Behavior: `ptr_offset_from_unsigned` called when first pointer has smaller address than second: $ADDR < $ADDR
   --> $DIR/ptr_offset_from_unsigned_neg.rs:LL:CC
    |
 LL |     let _val = unsafe { ptr1.sub_ptr(ptr2) };
-   |                         ^^^^^^^^^^^^^^^^^^ `ptr_offset_from_unsigned` called when first pointer has smaller offset than second: 0 < 4
+   |                         ^^^^^^^^^^^^^^^^^^ `ptr_offset_from_unsigned` called when first pointer has smaller address than second: $ADDR < $ADDR
    |
    = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
    = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information

tests/pass/ptr_int_from_exposed.rs

@@ -56,9 +56,18 @@ fn ptr_roundtrip_null() {
     assert_eq!(unsafe { *x_ptr_copy }, 42);
 }
 
+fn ptr_roundtrip_offset_from() {
+    let arr = [0; 5];
+    let begin = arr.as_ptr();
+    let end = begin.wrapping_add(arr.len());
+    let end_roundtrip = ptr::with_exposed_provenance::<i32>(end.expose_provenance());
+    unsafe { end_roundtrip.offset_from(begin) };
+}
+
 fn main() {
     ptr_roundtrip_out_of_bounds();
     ptr_roundtrip_confusion();
     ptr_roundtrip_imperfect();
     ptr_roundtrip_null();
+    ptr_roundtrip_offset_from();
 }