Revert "Merge pull request swiftlang#76656 from nate-chandler/rdar136388508"

This reverts commit b9228c8, reversing
changes made to 6fb2989.

After PR#76686 this bailout should no longer be neccessary.

rdar://136681998

Author: aschwaighofer

lib/SILOptimizer/Transforms/SILMem2Reg.cpp

@@ -2185,7 +2185,8 @@ bool MemoryToRegisters::promoteAllocation(AllocStackInst *alloc,
   ++NumAllocStackFound;
 
   // In OSSA, don't do Mem2Reg on non-trivial alloc_stack with dynamic_lifetime.
-  if (alloc->hasDynamicLifetime() && !alloc->getType().isTrivial(f)) {
+  if (alloc->hasDynamicLifetime() && f.hasOwnership() &&
+      !alloc->getType().isTrivial(f)) {
     return false;
   }
 

test/SILOptimizer/mem2reg.sil

@@ -578,21 +578,3 @@ bb0:
   dealloc_stack %11 : $*Pair<T, ()>
   return undef : $()
 }
-
-// CHECK-LABEL: sil @dont_promote_dynamic_lifetime : {{.*}} {
-// CHECK:         alloc_stack
-// CHECK-LABEL: } // end sil function 'dont_promote_dynamic_lifetime'
-sil @dont_promote_dynamic_lifetime : $@convention(thin) () -> () {
-  %stack = alloc_stack [dynamic_lifetime] $Klass
-  cond_br undef, left, right
-left:
-  %kin = apply undef() : $@convention(thin) () -> (@owned Klass)
-  %k = load %stack : $*Klass
-  strong_release %k : $Klass
-  br exit
-right:
-  br exit
-exit:
-  dealloc_stack %stack : $*Klass
-  return undef : $()
-}