We don't consider it profitable to jump thread when we could optimize arc in OSSA.

Copy propagation should be able to handle such cases without jump threading.

Author: meg-gupta

lib/SILOptimizer/Transforms/SimplifyCFG.cpp

@@ -944,14 +944,13 @@ bool SimplifyCFG::tryJumpThreading(BranchInst *BI) {
   for (unsigned i : indices(BI->getArgs())) {
     SILValue Arg = BI->getArg(i);
 
-    // TODO: Verify if we need to jump thread to remove releases in OSSA.
     // If the value being substituted on is release there is a chance we could
     // remove the release after jump threading.
-    if (!Arg->getType().isTrivial(*SrcBB->getParent()) &&
-        couldRemoveRelease(SrcBB, Arg, DestBB,
-                           DestBB->getArgument(i))) {
-        ThreadingBudget = 8;
-        break;
+    // In ossa, copy propagation can do this, avoid jump threading.
+    if (!Fn.hasOwnership() && !Arg->getType().isTrivial(*SrcBB->getParent()) &&
+        couldRemoveRelease(SrcBB, Arg, DestBB, DestBB->getArgument(i))) {
+      ThreadingBudget = 8;
+      break;
     }
 
     // If the value being substituted is an enum, check to see if there are any

test/SILOptimizer/simplify_cfg_ossa_disabled.sil

@@ -1198,46 +1198,3 @@ bb3(%4 : @guaranteed $Optional<Klass>):
   end_borrow %0a : $Klass
   return %5a : $Klass
 }
-
-// CHECK-LABEL: sil [ossa] @jump_thread_retain_release :
-// CHECK: cond_br
-// CHECK:   cond_br %3, bb4, bb3
-//
-// CHECK: bb3:
-// CHECK:   %3 = copy_value %2 : $Klass
-// CHECK:   destroy_value %2 : $Klass
-// CHECK:   br bb5(%3 : $Klass)
-//
-// CHECK: bb4:
-// CHECK:   %4 = copy_value %1 : $Klass
-// CHECK:   destroy_value %1 : $Klass
-// CHECK:   br bb5(%4 : $Klass)
-// CHECK: } // end sil function 'jump_thread_retain_release'
-sil [ossa] @jump_thread_retain_release : $@convention(thin) (Builtin.Int1, @owned Klass, @owned Klass, Builtin.Int1) -> () {
-bb0(%0 : $Builtin.Int1, %1 : @owned $Klass, %2 : @owned $Klass, %3 : $Builtin.Int1):
-  cond_br %0, bb2, bb1
-
-bb1:
-  br bb6(%2 : $Klass)
-
-bb2:
-  cond_br %3, bb3, bb4
-
-bb3:
-  %1a = copy_value %1 : $Klass
-  br bb5(%1a : $Klass)
-
-bb4:
-  %2a = copy_value %2 : $Klass
-  br bb5(%2a : $Klass)
-
-bb5(%11 : @owned $Klass):
-  destroy_value %2 : $Klass
-  br bb6(%11 : $Klass)
-
-bb6(%14 : @owned $Klass):
-  destroy_value %14 : $Klass
-  destroy_value %1 : $Klass
-  %16 = tuple ()
-  return %16 : $()
-}