From 8fb99afb0219846f98a82059de2f0808e4c0f61f Mon Sep 17 00:00:00 2001
From: Camille GILLOT <gillot.camille@gmail.com>
Date: Fri, 20 Oct 2023 15:24:09 +0000
Subject: [PATCH] Correct loop_headers logic.

---
 compiler/rustc_mir_transform/src/jump_threading.rs        | 4 ++--
 .../jump_threading.dfa.JumpThreading.panic-abort.diff     | 8 +-------
 .../jump_threading.dfa.JumpThreading.panic-unwind.diff    | 8 +-------
 3 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/jump_threading.rs b/compiler/rustc_mir_transform/src/jump_threading.rs
index 5a5ca6fa870..83af640f777 100644
--- a/compiler/rustc_mir_transform/src/jump_threading.rs
+++ b/compiler/rustc_mir_transform/src/jump_threading.rs
@@ -743,7 +743,7 @@ enum Update {
 /// Compute the set of loop headers in the given body. We define a loop header as a block which has
 /// at least a predecessor which it dominates. This definition is only correct for reducible CFGs.
 /// But if the CFG is already irreducible, there is no point in trying much harder.
-/// is already irreducibl
+/// is already irreducible.
 fn loop_headers(body: &Body<'_>) -> BitSet<BasicBlock> {
     let mut loop_headers = BitSet::new_empty(body.basic_blocks.len());
     let dominators = body.basic_blocks.dominators();
@@ -751,7 +751,7 @@ fn loop_headers(body: &Body<'_>) -> BitSet<BasicBlock> {
     for (bb, bbdata) in traversal::preorder(body) {
         for succ in bbdata.terminator().successors() {
             if dominators.dominates(succ, bb) {
-                loop_headers.insert(bb);
+                loop_headers.insert(succ);
             }
         }
     }
diff --git a/tests/mir-opt/jump_threading.dfa.JumpThreading.panic-abort.diff b/tests/mir-opt/jump_threading.dfa.JumpThreading.panic-abort.diff
index 01bddc9a173..ad5846c97de 100644
--- a/tests/mir-opt/jump_threading.dfa.JumpThreading.panic-abort.diff
+++ b/tests/mir-opt/jump_threading.dfa.JumpThreading.panic-abort.diff
@@ -19,8 +19,7 @@
           StorageLive(_1);
           _1 = DFA::A;
           StorageLive(_2);
--         goto -> bb1;
-+         goto -> bb7;
+          goto -> bb1;
       }
   
       bb1: {
@@ -64,11 +63,6 @@
           _3 = const ();
           StorageDead(_7);
           goto -> bb1;
-+     }
-+ 
-+     bb7: {
-+         _4 = discriminant(_1);
-+         goto -> bb4;
       }
   }
   
diff --git a/tests/mir-opt/jump_threading.dfa.JumpThreading.panic-unwind.diff b/tests/mir-opt/jump_threading.dfa.JumpThreading.panic-unwind.diff
index 01bddc9a173..ad5846c97de 100644
--- a/tests/mir-opt/jump_threading.dfa.JumpThreading.panic-unwind.diff
+++ b/tests/mir-opt/jump_threading.dfa.JumpThreading.panic-unwind.diff
@@ -19,8 +19,7 @@
           StorageLive(_1);
           _1 = DFA::A;
           StorageLive(_2);
--         goto -> bb1;
-+         goto -> bb7;
+          goto -> bb1;
       }
   
       bb1: {
@@ -64,11 +63,6 @@
           _3 = const ();
           StorageDead(_7);
           goto -> bb1;
-+     }
-+ 
-+     bb7: {
-+         _4 = discriminant(_1);
-+         goto -> bb4;
       }
   }