analyze: run equiv remapping before pointee_type pass

c2rust-analyze/src/analyze.rs

@@ -587,45 +587,18 @@ fn run(tcx: TyCtxt) {
     do_recent_writes(&gacx, &mut func_info, &all_fn_ldids);
 
     // ----------------------------------
-    // Infer pointee types
-    // ----------------------------------
-
-    let mut global_pointee_types = do_pointee_type(&mut gacx, &mut func_info, &all_fn_ldids);
-    debug_print_pointee_types(
-        &mut gacx,
-        &mut func_info,
-        &all_fn_ldids,
-        &global_pointee_types,
-    );
-
-    // ----------------------------------
-    // Compute dataflow constraints
+    // Remap `PointerId`s by equivalence class
     // ----------------------------------
 
-    // Initial pass to assign local `PointerId`s and gather equivalence constraints, which state
-    // that two pointer types must be converted to the same reference type.  Some additional data
-    // computed during this the process is kept around for use in later passes.
+    // Initial pass to gather equivalence constraints, which state that two pointer types must be
+    // converted to the same reference type.  Some additional data computed during this the process
+    // is kept around for use in later passes.
     let global_equiv = build_equiv_constraints(&mut gacx, &mut func_info, &all_fn_ldids);
-    build_dataflow_constraints(
-        &mut gacx,
-        &mut func_info,
-        &all_fn_ldids,
-        &global_pointee_types,
-    );
-
-    // ----------------------------------
-    // Remap `PointerId`s by equivalence class
-    // ----------------------------------
 
     // Remap pointers based on equivalence classes, so all members of an equivalence class now use
     // the same `PointerId`.
     let (global_counter, global_equiv_map) = global_equiv.renumber();
     debug!("global_equiv_map = {global_equiv_map:?}");
-    pointee_type::remap_pointers_global(
-        &mut global_pointee_types,
-        &global_equiv_map,
-        global_counter.num_pointers(),
-    );
     gacx.remap_pointers(&global_equiv_map, global_counter.num_pointers());
 
     let mut local_counter = global_counter.into_local();
@@ -637,15 +610,6 @@ fn run(tcx: TyCtxt) {
             .local_equiv
             .renumber(&global_equiv_map, &mut local_counter);
         debug!("local_equiv_map = {local_equiv_map:?}");
-        if info.local_pointee_types.is_set() {
-            pointee_type::remap_pointers_local(
-                &mut global_pointee_types,
-                &mut info.local_pointee_types,
-                global_equiv_map.and(&local_equiv_map),
-                local_base,
-                local_count,
-            );
-        }
         info.acx_data.remap_pointers(
             &mut gacx,
             global_equiv_map.and(&local_equiv_map),
@@ -659,6 +623,32 @@ fn run(tcx: TyCtxt) {
         info.local_equiv.clear();
     }
 
+    // ----------------------------------
+    // Infer pointee types
+    // ----------------------------------
+
+    // This runs after equivalence class remapping because it lets us get better pointee results in
+    // pointer-to-pointer cases without implementing full type unification.
+
+    let global_pointee_types = do_pointee_type(&mut gacx, &mut func_info, &all_fn_ldids);
+    debug_print_pointee_types(
+        &mut gacx,
+        &mut func_info,
+        &all_fn_ldids,
+        &global_pointee_types,
+    );
+
+    // ----------------------------------
+    // Compute dataflow constraints
+    // ----------------------------------
+
+    build_dataflow_constraints(
+        &mut gacx,
+        &mut func_info,
+        &all_fn_ldids,
+        &global_pointee_types,
+    );
+
     // ----------------------------------
     // Build initial assignment
     // ----------------------------------

c2rust-analyze/src/pointee_type/mod.rs

@@ -1,7 +1,5 @@
 use crate::context::AnalysisCtxt;
-use crate::pointer_id::{GlobalPointerTable, LocalPointerTable, PointerId, PointerTable};
 use rustc_middle::mir::Body;
-use std::mem;
 
 mod constraint_set;
 mod solve;
@@ -17,34 +15,3 @@ pub fn generate_constraints<'tcx>(
 ) -> ConstraintSet<'tcx> {
     type_check::visit(acx, mir, vars)
 }
-
-pub fn remap_pointers_global<'tcx>(
-    pointee_types: &mut GlobalPointerTable<PointeeTypes<'tcx>>,
-    map: &GlobalPointerTable<PointerId>,
-    count: usize,
-) {
-    let mut old = mem::replace(pointee_types, GlobalPointerTable::new(count));
-    let new = pointee_types;
-    for (old_ptr, old_val) in old.iter_mut() {
-        // If there are multiple old pointers that map to the same new pointer, merge their sets.
-        new[map[old_ptr]].merge(mem::take(old_val));
-    }
-}
-
-pub fn remap_pointers_local<'tcx>(
-    global_pointee_types: &mut GlobalPointerTable<PointeeTypes<'tcx>>,
-    local_pointee_types: &mut LocalPointerTable<PointeeTypes<'tcx>>,
-    map: PointerTable<PointerId>,
-    local_base: u32,
-    local_count: usize,
-) {
-    let mut old = mem::replace(
-        local_pointee_types,
-        LocalPointerTable::new(local_base, local_count),
-    );
-    let mut new = global_pointee_types.and_mut(local_pointee_types);
-    for (old_ptr, old_val) in old.iter_mut() {
-        // If there are multiple old pointers that map to the same new pointer, merge their sets.
-        new[map[old_ptr]].merge(mem::take(old_val));
-    }
-}

c2rust-analyze/src/pointee_type/solve.rs

@@ -145,10 +145,6 @@ impl<'tcx> PointeeTypes<'tcx> {
         }
     }
 
-    pub fn merge(&mut self, other: PointeeTypes<'tcx>) {
-        self.tys.extend(other.tys);
-    }
-
     pub fn simplify(&mut self, vars: &VarTable<'tcx>) {
         let mut add = Vec::new();
         let mut remove = Vec::new();

c2rust-analyze/tests/filecheck/pointee.rs

@@ -34,7 +34,9 @@ unsafe fn remove_cast() {
 unsafe fn malloc_fresh() {
     let mut p = 0 as *mut libc::c_void;
     let fresh = &mut p;
-    // CHECK: malloc(4)
+    // CHECK-NOT: malloc(4)
+    // CHECK: Box::new
+    // CHECK-NOT: malloc(4)
     let q = malloc(4);
     *fresh = q;
     *(p as *mut i32) = 1;