Merge pull request #29249 from atrick/fix-stackpromote

Fix EscapeAnalysis losing precision during merge.

Author: atrick

lib/SILOptimizer/Analysis/EscapeAnalysis.cpp

@@ -732,9 +732,13 @@ void EscapeAnalysis::ConnectionGraph::mergeAllScheduledNodes() {
     From->isMerged = true;
 
     if (From->mappedValue) {
-      if (To->mappedValue)
-        Values2Nodes.erase(From->mappedValue);
-      else {
+      // If possible, transfer 'From's mappedValue to 'To' for clarity. Any
+      // values previously mapped to 'From' but not transferred to 'To's
+      // mappedValue must remain mapped to 'From'. Lookups on those values will
+      // find 'To' via the mergeTarget. Dropping a value's mapping is illegal
+      // because it could cause a node to be recreated without the edges that
+      // have already been discovered.
+      if (!To->mappedValue) {
         To->mappedValue = From->mappedValue;
         Values2Nodes[To->mappedValue] = To;
       }

test/SILOptimizer/escape_analysis.sil

@@ -1817,47 +1817,3 @@ bb0(%0 : $IntWrapper):
   %tuple = tuple (%bridge : $Builtin.BridgeObject, %ump : $UnsafeMutablePointer<Int64>)
   return %tuple : $(Builtin.BridgeObject, UnsafeMutablePointer<Int64>)
 }
-
-// =============================================================================
-// Test call to array.uninitialized that has extra release_value uses
-
-class DummyArrayStorage<Element> {
-  @_hasStorage var count: Int { get }
-  @_hasStorage var capacity: Int { get }
-  init()
-}
-
-// init_any_array_with_buffer
-sil [_semantics "array.uninitialized"] @init_any_array_with_buffer : $@convention(thin) (@owned DummyArrayStorage<AnyObject>, Int32, @thin Array<AnyObject>.Type) -> (@owned Array<AnyObject>, UnsafeMutablePointer<AnyObject>)
-
-// CHECK-LABEL: CG of testBadArrayUninit
-// CHECK-NEXT:  Val [ref] %2 Esc: , Succ: (%2.1)
-// CHECK-NEXT:  Con [int] %2.1 Esc: G, Succ: (%2.2)
-// CHECK-NEXT:  Con [ref] %2.2 Esc: G, Succ:
-// CHECK-NEXT:  Val %5 Esc: , Succ: (%5.1)
-// CHECK-NEXT:  Con %5.1 Esc: G, Succ: %10
-// CHECK-NEXT:  Val [ref] %10 Esc: G, Succ: (%10.1)
-// CHECK-NEXT:  Con %10.1 Esc: G, Succ:
-// CHECK-LABEL: End
-sil hidden @testBadArrayUninit : $@convention(thin) (Builtin.Word, Int32) -> () {
-bb0(%0 : $Builtin.Word, %1 : $Int32):
-  // create an array
-  %2 = alloc_ref [tail_elems $AnyObject * %0 : $Builtin.Word] $DummyArrayStorage<AnyObject>
-  %3 = metatype $@thin Array<AnyObject>.Type
-  %4 = function_ref @init_any_array_with_buffer : $@convention(thin) (@owned DummyArrayStorage<AnyObject>, Int32, @thin Array<AnyObject>.Type) -> (@owned Array<AnyObject>, UnsafeMutablePointer<AnyObject>)
-  %5 = apply %4(%2, %1, %3) : $@convention(thin) (@owned DummyArrayStorage<AnyObject>, Int32, @thin Array<AnyObject>.Type) -> (@owned Array<AnyObject>, UnsafeMutablePointer<AnyObject>)
-  %6 = tuple_extract %5 : $(Array<AnyObject>, UnsafeMutablePointer<AnyObject>), 0
-  %7 = tuple_extract %5 : $(Array<AnyObject>, UnsafeMutablePointer<AnyObject>), 1
-  %8 = struct_extract %7 : $UnsafeMutablePointer<AnyObject>, #UnsafeMutablePointer._rawValue
-  %9 = pointer_to_address %8 : $Builtin.RawPointer to [strict] $*AnyObject
-
-  // store an elt
-  %10 = alloc_ref $C
-  %11 = init_existential_ref %10 : $C : $C, $AnyObject
-  store %11 to %9 : $*AnyObject
-
-  // extra use of the call
-  release_value %5 : $(Array<AnyObject>, UnsafeMutablePointer<AnyObject>) // id: %228
-  %13 = tuple ()
-  return %13 : $()
-}