Auto merge of #130455 - compiler-errors:inline-ordering, r=saethlin

Remove semi-nondeterminism of `DefPathHash` ordering from inliner

Déjà vu or something because I kinda thought I had put this PR up before. I recall a discussion somewhere where I think it was `@saethlin` mentioning that this check was no longer needed since we have "proper" cycle detection. Putting that up as a PR now.

This may slighlty negatively affect inlining, since the cycle breaking here means that we still inlined some cycles when the def path hashes were ordered in certain ways, this leads to really bad nondeterminism that makes minimizing ICEs and putting up inliner bugfixes difficult.

r? `@cjgillot` or `@saethlin` or someone else idk

6 files changed, 4 insertions, 72 deletions

diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 870cb180ce1..2de75e2ef50 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -357,16 +357,6 @@ impl<'tcx> Inliner<'tcx> {
         }
 
         if callee_def_id.is_local() {
-            // Avoid a cycle here by only using `instance_mir` only if we have
-            // a lower `DefPathHash` than the callee. This ensures that the callee will
-            // not inline us. This trick even works with incremental compilation,
-            // since `DefPathHash` is stable.
-            if self.tcx.def_path_hash(caller_def_id).local_hash()
-                < self.tcx.def_path_hash(callee_def_id).local_hash()
-            {
-                return Ok(());
-            }
-
             // If we know for sure that the function we're calling will itself try to
             // call us, then we avoid inlining that function.
             if self.tcx.mir_callgraph_reachable((callee, caller_def_id.expect_local())) {
diff --git a/tests/mir-opt/inline/cycle.main.Inline.panic-abort.diff b/tests/mir-opt/inline/cycle.main.Inline.panic-abort.diff
index fd1f698c60d..6522ed6bffd 100644
--- a/tests/mir-opt/inline/cycle.main.Inline.panic-abort.diff
+++ b/tests/mir-opt/inline/cycle.main.Inline.panic-abort.diff
@@ -4,35 +4,16 @@
   fn main() -> () {
       let mut _0: ();
       let _1: ();
-+     let mut _2: fn() {g};
-+     scope 1 (inlined f::<fn() {g}>) {
-+         debug g => _2;
-+         let mut _3: &fn() {g};
-+         let _4: ();
-+     }
   
       bb0: {
           StorageLive(_1);
--         _1 = f::<fn() {g}>(g) -> [return: bb1, unwind unreachable];
-+         StorageLive(_2);
-+         _2 = g;
-+         StorageLive(_4);
-+         StorageLive(_3);
-+         _3 = &_2;
-+         _4 = <fn() {g} as Fn<()>>::call(move _3, const ()) -> [return: bb2, unwind unreachable];
+          _1 = f::<fn() {g}>(g) -> [return: bb1, unwind unreachable];
       }
   
       bb1: {
-+         StorageDead(_4);
-+         StorageDead(_2);
           StorageDead(_1);
           _0 = const ();
           return;
-+     }
-+ 
-+     bb2: {
-+         StorageDead(_3);
-+         drop(_2) -> [return: bb1, unwind unreachable];
       }
   }
   
diff --git a/tests/mir-opt/inline/cycle.main.Inline.panic-unwind.diff b/tests/mir-opt/inline/cycle.main.Inline.panic-unwind.diff
index e8299db47db..7a25830a4d0 100644
--- a/tests/mir-opt/inline/cycle.main.Inline.panic-unwind.diff
+++ b/tests/mir-opt/inline/cycle.main.Inline.panic-unwind.diff
@@ -4,43 +4,16 @@
   fn main() -> () {
       let mut _0: ();
       let _1: ();
-+     let mut _2: fn() {g};
-+     scope 1 (inlined f::<fn() {g}>) {
-+         debug g => _2;
-+         let mut _3: &fn() {g};
-+         let _4: ();
-+     }
   
       bb0: {
           StorageLive(_1);
--         _1 = f::<fn() {g}>(g) -> [return: bb1, unwind continue];
-+         StorageLive(_2);
-+         _2 = g;
-+         StorageLive(_4);
-+         StorageLive(_3);
-+         _3 = &_2;
-+         _4 = <fn() {g} as Fn<()>>::call(move _3, const ()) -> [return: bb2, unwind: bb3];
+          _1 = f::<fn() {g}>(g) -> [return: bb1, unwind continue];
       }
   
       bb1: {
-+         StorageDead(_4);
-+         StorageDead(_2);
           StorageDead(_1);
           _0 = const ();
           return;
-+     }
-+ 
-+     bb2: {
-+         StorageDead(_3);
-+         drop(_2) -> [return: bb1, unwind continue];
-+     }
-+ 
-+     bb3 (cleanup): {
-+         drop(_2) -> [return: bb4, unwind terminate(cleanup)];
-+     }
-+ 
-+     bb4 (cleanup): {
-+         resume;
       }
   }
   
diff --git a/tests/mir-opt/inline/cycle.rs b/tests/mir-opt/inline/cycle.rs
index cb50638473f..383d0796a88 100644
--- a/tests/mir-opt/inline/cycle.rs
+++ b/tests/mir-opt/inline/cycle.rs
@@ -19,9 +19,5 @@ fn g() {
 
 // EMIT_MIR cycle.main.Inline.diff
 fn main() {
-    // CHECK-LABEL: fn main(
-    // CHECK-NOT: inlined
-    // CHECK: (inlined f::<fn() {g}>)
-    // CHECK-NOT: inlined
     f(g);
 }
diff --git a/tests/mir-opt/inline/inline_cycle_generic.main.Inline.panic-abort.diff b/tests/mir-opt/inline/inline_cycle_generic.main.Inline.panic-abort.diff
index 142b9c56598..d437dbf5763 100644
--- a/tests/mir-opt/inline/inline_cycle_generic.main.Inline.panic-abort.diff
+++ b/tests/mir-opt/inline/inline_cycle_generic.main.Inline.panic-abort.diff
@@ -7,10 +7,6 @@
 +     scope 1 (inlined <C as Call>::call) {
 +         scope 2 (inlined <B<A> as Call>::call) {
 +             scope 3 (inlined <A as Call>::call) {
-+                 scope 4 (inlined <B<C> as Call>::call) {
-+                     scope 5 (inlined <C as Call>::call) {
-+                     }
-+                 }
 +             }
 +         }
 +     }
@@ -18,7 +14,7 @@
       bb0: {
           StorageLive(_1);
 -         _1 = <C as Call>::call() -> [return: bb1, unwind unreachable];
-+         _1 = <B<A> as Call>::call() -> [return: bb1, unwind unreachable];
++         _1 = <B<C> as Call>::call() -> [return: bb1, unwind unreachable];
       }
   
       bb1: {
diff --git a/tests/mir-opt/inline/inline_cycle_generic.main.Inline.panic-unwind.diff b/tests/mir-opt/inline/inline_cycle_generic.main.Inline.panic-unwind.diff
index 193ada05f02..8314526ee04 100644
--- a/tests/mir-opt/inline/inline_cycle_generic.main.Inline.panic-unwind.diff
+++ b/tests/mir-opt/inline/inline_cycle_generic.main.Inline.panic-unwind.diff
@@ -7,10 +7,6 @@
 +     scope 1 (inlined <C as Call>::call) {
 +         scope 2 (inlined <B<A> as Call>::call) {
 +             scope 3 (inlined <A as Call>::call) {
-+                 scope 4 (inlined <B<C> as Call>::call) {
-+                     scope 5 (inlined <C as Call>::call) {
-+                     }
-+                 }
 +             }
 +         }
 +     }
@@ -18,7 +14,7 @@
       bb0: {
           StorageLive(_1);
 -         _1 = <C as Call>::call() -> [return: bb1, unwind continue];
-+         _1 = <B<A> as Call>::call() -> [return: bb1, unwind continue];
++         _1 = <B<C> as Call>::call() -> [return: bb1, unwind continue];
       }
   
       bb1: {