Rollup merge of #145744 - RalfJung:miri-inplace-aliasing, r=compiler-errors

miri: also detect aliasing of in-place argument and return place

This is a follow-up to rust-lang/rust#145585 where I forgot to deal with the case of the return place aliasing an in-place argument -- as ``@Amanieu`` mentioned in rust-lang/rust#71117 (comment), that case must also be forbidden.

r? ``@compiler-errors``

Author: samueltardieu

tests/fail/function_calls/arg_inplace_locals_alias.rs

@@ -1,3 +1,5 @@
+//! Ensure we detect aliasing of two in-place arguments for the tricky case where they do not
+//! live in memory.
 //@revisions: stack tree
 //@[tree]compile-flags: -Zmiri-tree-borrows
 // Validation forces more things into memory, which we can't have here.

tests/fail/function_calls/arg_inplace_locals_alias_ret.rs

@@ -0,0 +1,34 @@
+//! Ensure we detect aliasing of a in-place argument with the return place for the tricky case where
+//! they do not live in memory.
+//@revisions: stack tree
+//@[tree]compile-flags: -Zmiri-tree-borrows
+// Validation forces more things into memory, which we can't have here.
+//@compile-flags: -Zmiri-disable-validation
+#![feature(custom_mir, core_intrinsics)]
+use std::intrinsics::mir::*;
+
+#[allow(unused)]
+pub struct S(i32);
+
+#[custom_mir(dialect = "runtime", phase = "optimized")]
+fn main() {
+    mir! {
+        let _unit: ();
+        {
+            let staging = S(42); // This forces `staging` into memory...
+            let _non_copy = staging; // ... so we move it to a non-inmemory local here.
+            // This specifically uses a type with scalar representation to tempt Miri to use the
+            // efficient way of storing local variables (outside adressable memory).
+            Call(_non_copy = callee(Move(_non_copy)), ReturnTo(after_call), UnwindContinue())
+            //~[stack]^ ERROR: not granting access
+            //~[tree]| ERROR: /reborrow .* forbidden/
+        }
+        after_call = {
+            Return()
+        }
+    }
+}
+
+pub fn callee(x: S) -> S {
+    x
+}

tests/fail/function_calls/arg_inplace_locals_alias_ret.stack.stderr

@@ -0,0 +1,25 @@
+error: Undefined Behavior: not granting access to tag <TAG> because that would remove [Unique for <TAG>] which is strongly protected
+  --> tests/fail/function_calls/arg_inplace_locals_alias_ret.rs:LL:CC
+   |
+LL |             Call(_non_copy = callee(Move(_non_copy)), ReturnTo(after_call), UnwindContinue())
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Undefined Behavior occurred here
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental
+   = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information
+help: <TAG> was created here, as the root tag for ALLOC
+  --> tests/fail/function_calls/arg_inplace_locals_alias_ret.rs:LL:CC
+   |
+LL |             Call(_non_copy = callee(Move(_non_copy)), ReturnTo(after_call), UnwindContinue())
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: <TAG> is this argument
+  --> tests/fail/function_calls/arg_inplace_locals_alias_ret.rs:LL:CC
+   |
+LL |     x
+   |     ^
+   = note: BACKTRACE (of the first span):
+   = note: inside `main` at tests/fail/function_calls/arg_inplace_locals_alias_ret.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+

tests/fail/function_calls/arg_inplace_locals_alias_ret.tree.stderr

@@ -0,0 +1,34 @@
+error: Undefined Behavior: reborrow through <TAG> (root of the allocation) at ALLOC[0x0] is forbidden
+  --> tests/fail/function_calls/arg_inplace_locals_alias_ret.rs:LL:CC
+   |
+LL |             Call(_non_copy = callee(Move(_non_copy)), ReturnTo(after_call), UnwindContinue())
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Undefined Behavior occurred here
+   |
+   = help: this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental
+   = help: see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/tree-borrows.md for further information
+   = help: the accessed tag <TAG> (root of the allocation) is foreign to the protected tag <TAG> (i.e., it is not a child)
+   = help: this reborrow (acting as a foreign read access) would cause the protected tag <TAG> (currently Active) to become Disabled
+   = help: protected tags must never be Disabled
+help: the accessed tag <TAG> was created here
+  --> tests/fail/function_calls/arg_inplace_locals_alias_ret.rs:LL:CC
+   |
+LL |             Call(_non_copy = callee(Move(_non_copy)), ReturnTo(after_call), UnwindContinue())
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+help: the protected tag <TAG> was created here, in the initial state Reserved
+  --> tests/fail/function_calls/arg_inplace_locals_alias_ret.rs:LL:CC
+   |
+LL |     x
+   |     ^
+help: the protected tag <TAG> later transitioned to Active due to a child write access at offsets [0x0..0x4]
+  --> tests/fail/function_calls/arg_inplace_locals_alias_ret.rs:LL:CC
+   |
+LL |     x
+   |     ^
+   = help: this transition corresponds to the first write to a 2-phase borrowed mutable reference
+   = note: BACKTRACE (of the first span):
+   = note: inside `main` at tests/fail/function_calls/arg_inplace_locals_alias_ret.rs:LL:CC
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+error: aborting due to 1 previous error
+