Discard raw pointers from SSA locals.

Author: cjgillot

compiler/rustc_mir_transform/src/copy_prop.rs

@@ -117,8 +117,10 @@ impl<'tcx> Visitor<'tcx> for SsaLocals {
                 self.assignments[local].insert(LocationExtended::Plain(loc));
                 self.assignment_order.push(local);
             }
-            PlaceContext::MutatingUse(_) => self.assignments[local] = Set1::Many,
-            // Immutable borrows and AddressOf are taken into account in `SsaLocals::new` by
+            // Anything can happen with raw pointers, so remove them.
+            PlaceContext::NonMutatingUse(NonMutatingUseContext::AddressOf)
+            | PlaceContext::MutatingUse(_) => self.assignments[local] = Set1::Many,
+            // Immutable borrows are taken into account in `SsaLocals::new` by
             // removing non-freeze locals.
             PlaceContext::NonMutatingUse(_) => {
                 let set = &mut self.assignments[local];

tests/mir-opt/copy-prop/mutate_through_pointer.f.CopyProp.diff

@@ -0,0 +1,19 @@
+- // MIR for `f` before CopyProp
++ // MIR for `f` after CopyProp
+  
+  fn f(_1: bool) -> bool {
+      let mut _0: bool;                    // return place in scope 0 at $DIR/mutate_through_pointer.rs:+0:18: +0:22
+      let mut _2: bool;                    // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+      let mut _3: *const bool;             // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+      let mut _4: *mut bool;               // in scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+  
+      bb0: {
+          _2 = _1;                         // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+          _3 = &raw const _2;              // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+          _4 = &raw mut (*_3);             // scope 0 at $SRC_DIR/core/src/intrinsics/mir.rs:LL:COL
+          (*_4) = const false;             // scope 0 at $DIR/mutate_through_pointer.rs:+5:9: +5:20
+          _0 = _1;                         // scope 0 at $DIR/mutate_through_pointer.rs:+6:9: +6:16
+          return;                          // scope 0 at $DIR/mutate_through_pointer.rs:+7:9: +7:17
+      }
+  }
+  

tests/mir-opt/copy-prop/mutate_through_pointer.rs

@@ -0,0 +1,22 @@
+#![feature(custom_mir, core_intrinsics)]
+#![allow(unused_assignments)]
+extern crate core;
+use core::intrinsics::mir::*;
+
+#[custom_mir(dialect = "analysis", phase = "post-cleanup")]
+fn f(c: bool) -> bool {
+    mir!({
+        let a = c;
+        let p = core::ptr::addr_of!(a);
+        let p2 = core::ptr::addr_of_mut!(*p);
+        *p2 = false;
+        RET = c;
+        Return()
+    })
+}
+
+fn main() {
+    assert_eq!(true, f(true));
+}
+
+// EMIT_MIR mutate_through_pointer.f.CopyProp.diff