Auto merge of #148259 - RalfJung:const-ptr-fragment, r=oli-obk

const-eval: fix and re-enable pointer fragment support

The pointer fragment support from rust-lang/rust#144081 got disabled due to rust-lang/rust#146291. This brings it back. To fix the issue, the per-byte provenance fragment tracking tracks *both* the provenance and raw address of the full pointer, so we can ensure that only fragments that are truly part of the same pointer are being merged.

r? `@oli-obk`
Cc `@theemathas`
Fixes rust-lang/const-eval#72 again.
Also fixes rust-lang/rust#147959.

`@traviscross` I assume this won't need another t-lang FCP since it already got FCP'd in rust-lang/rust#144081?

Author: bors

src/machine.rs

@@ -351,21 +351,6 @@ impl interpret::Provenance for Provenance {
         }
         Ok(())
     }
-
-    fn join(left: Self, right: Self) -> Option<Self> {
-        match (left, right) {
-            // If both are the *same* concrete tag, that is the result.
-            (
-                Provenance::Concrete { alloc_id: left_alloc, tag: left_tag },
-                Provenance::Concrete { alloc_id: right_alloc, tag: right_tag },
-            ) if left_alloc == right_alloc && left_tag == right_tag => Some(left),
-            // If one side is a wildcard, the best possible outcome is that it is equal to the other
-            // one, and we use that.
-            (Provenance::Wildcard, o) | (o, Provenance::Wildcard) => Some(o),
-            // Otherwise, fall back to `None`.
-            _ => None,
-        }
-    }
 }
 
 impl fmt::Debug for ProvenanceExtra {

src/shims/native_lib/mod.rs

@@ -256,7 +256,9 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 match evt {
                     AccessEvent::Read(_) => {
                         // If a provenance was read by the foreign code, expose it.
-                        for prov in alloc.provenance().get_range(this, overlap.into()) {
+                        for (_prov_range, prov) in
+                            alloc.provenance().get_range(overlap.into(), this)
+                        {
                             this.expose_provenance(prov)?;
                         }
                     }
@@ -321,7 +323,8 @@ trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 // Expose all provenances in the allocation within the byte range of the struct, if
                 // any. These pointers are being directly passed to native code by-value.
                 let alloc = this.get_alloc_raw(id)?;
-                for prov in alloc.provenance().get_range(this, range.clone().into()) {
+                for (_prov_range, prov) in alloc.provenance().get_range(range.clone().into(), this)
+                {
                     expose(prov)?;
                 }
                 // Read the bytes that make up this argument. We cannot use the normal getter as