[pmo] Eliminate incomplete support for promoting enums.

This was never implemented correctly way back in 2013-2014. It was originally
added I believe so we could DI checks, but the promotion part was never added.

Given that DI is now completely split from PMO, we can just turn this off and if
necessary add it back on master "properly".

rdar://41161408
(cherry picked from commit b9f69cb)

Author: gottesmm

lib/SILOptimizer/Mandatory/PMOMemoryUseCollector.cpp

@@ -231,10 +231,6 @@ class ElementUseCollector {
   /// element we attribute an access to.
   bool InStructSubElement = false;
 
-  /// When walking the use list, if we index into an enum slice, keep track
-  /// of this.
-  bool InEnumSubElement = false;
-
 public:
   ElementUseCollector(const PMOMemoryObjectInfo &TheMemory,
                       SmallVectorImpl<PMOMemoryUse> &Uses,
@@ -294,7 +290,7 @@ void ElementUseCollector::addElementUses(unsigned BaseEltNo, SILType UseTy,
   // If we're in a subelement of a struct or enum, just mark the struct, not
   // things that come after it in a parent tuple.
   unsigned NumElements = 1;
-  if (TheMemory.NumElements != 1 && !InStructSubElement && !InEnumSubElement)
+  if (TheMemory.NumElements != 1 && !InStructSubElement)
     NumElements = getElementCountRec(Module, UseTy);
 
   Uses.push_back(PMOMemoryUse(User, Kind, BaseEltNo, NumElements));
@@ -309,7 +305,7 @@ bool ElementUseCollector::collectTupleElementUses(TupleElementAddrInst *TEAI,
   // If we're walking into a tuple within a struct or enum, don't adjust the
   // BaseElt.  The uses hanging off the tuple_element_addr are going to be
   // counted as uses of the struct or enum itself.
-  if (InStructSubElement || InEnumSubElement)
+  if (InStructSubElement)
     return collectUses(TEAI, BaseEltNo);
 
   // tuple_element_addr P, 42 indexes into the current tuple element.
@@ -554,26 +550,6 @@ bool ElementUseCollector::collectUses(SILValue Pointer, unsigned BaseEltNo) {
       llvm_unreachable("bad parameter convention");
     }
 
-    // init_enum_data_addr is treated like a tuple_element_addr or other
-    // instruction that is looking into the memory object (i.e., the memory
-    // object needs to be explicitly initialized by a copy_addr or some other
-    // use of the projected address).
-    if (auto I = dyn_cast<InitEnumDataAddrInst>(User)) {
-      // If we are in a struct already, bail. With proper analysis, we should be
-      // able to do this optimization.
-      if (InStructSubElement) {
-        return false;
-      }
-
-      // Keep track of the fact that we're inside of an enum.  This informs our
-      // recursion that tuple stores are not scalarized outside, and that stores
-      // should not be treated as partial stores.
-      llvm::SaveAndRestore<bool> X(InEnumSubElement, true);
-      if (!collectUses(I, BaseEltNo))
-        return false;
-      continue;
-    }
-
     // init_existential_addr is modeled as an initialization store.
     if (isa<InitExistentialAddrInst>(User)) {
       // init_existential_addr should not apply to struct subelements.
@@ -585,17 +561,6 @@ bool ElementUseCollector::collectUses(SILValue Pointer, unsigned BaseEltNo) {
       continue;
     }
 
-    // inject_enum_addr is modeled as an initialization store.
-    if (isa<InjectEnumAddrInst>(User)) {
-      // inject_enum_addr the subelement of a struct unless in a ctor.
-      if (InStructSubElement) {
-        return false;
-      }
-      Uses.push_back(
-          PMOMemoryUse(User, PMOUseKind::Initialization, BaseEltNo, 1));
-      continue;
-    }
-
     // open_existential_addr is a use of the protocol value,
     // so it is modeled as a load.
     if (isa<OpenExistentialAddrInst>(User)) {

test/SILOptimizer/predictable_memopt.sil

@@ -880,4 +880,24 @@ bb0(%arg : $K):
   %4 = load %0 : $*SWithOpt
   dealloc_stack %0 : $*SWithOpt
   return %4 : $SWithOpt
-}
+}
+
+// We do not support this now, so make sure we do not do anything.
+//
+// CHECK-LABEL: sil @promote_init_enum_data_addr : $@convention(thin)
+// CHECK: alloc_stack
+// CHECK: load
+// CHECK: [[RESULT:%.*]] = load
+// CHECK: return [[RESULT]]
+// CHECK: } // end sil function 'promote_init_enum_data_addr'
+sil @promote_init_enum_data_addr : $@convention(thin) (@in Int) -> Int {
+bb0(%0 : $*Int):
+  %1 = alloc_stack $Optional<Int>
+  %2 = load %0 : $*Int
+  %3 = init_enum_data_addr %1 : $*Optional<Int>, #Optional.some!enumelt.1
+  store %2 to %3 : $*Int
+  inject_enum_addr %1 : $*Optional<Int>, #Optional.some!enumelt.1
+  %4 = load %3 : $*Int
+  dealloc_stack %1 : $*Optional<Int>
+  return %4 : $Int
+}