Merge pull request #70243 from meg-gupta/enableedgecase

Handle `unchecked_ref_cast` in ObjectOutliner

Author: meg-gupta

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/ObjectOutliner.swift

@@ -85,6 +85,10 @@ private func findEndCOWMutation(of object: Value) -> EndCOWMutationInst? {
       if let ecm = findEndCOWMutation(of: uci) {
         return ecm
       }
+    case let urci as UncheckedRefCastInst:
+      if let ecm = findEndCOWMutation(of: urci) {
+        return ecm
+      }
     case let mv as MoveValueInst:
       if let ecm = findEndCOWMutation(of: mv) {
         return ecm
@@ -134,6 +138,10 @@ private func findInitStores(of object: Value,
       if !findInitStores(of: uci, &fieldStores, &tailStores) {
         return false
       }
+    case let urci as UncheckedRefCastInst:
+      if !findInitStores(of: urci, &fieldStores, &tailStores) {
+        return false
+      }
     case let mvi as MoveValueInst:
       if !findInitStores(of: mvi, &fieldStores, &tailStores) {
         return false
@@ -342,6 +350,8 @@ private func rewriteUses(of startValue: Value, _ context: FunctionPassContext) {
       context.erase(instruction: endMutation)
     case let upCast as UpcastInst:
       worklist.pushIfNotVisited(usersOf: upCast)
+    case let refCast as UncheckedRefCastInst:
+      worklist.pushIfNotVisited(usersOf: refCast)
     case let moveValue as MoveValueInst:
       worklist.pushIfNotVisited(usersOf: moveValue)
     case is DeallocRefInst, is DeallocStackRefInst:

lib/SILOptimizer/Transforms/COWOpts.cpp

@@ -119,6 +119,9 @@ static SILValue skipStructAndExtract(SILValue value) {
 }
 
 bool COWOptsPass::optimizeBeginCOW(BeginCOWMutationInst *BCM) {
+  LLVM_DEBUG(llvm::dbgs() << "Looking at: ");
+  LLVM_DEBUG(BCM->dump());
+
   SILFunction *function = BCM->getFunction();
   StackList<EndCOWMutationInst *> endCOWMutationInsts(function);
   InstructionSet endCOWMutationsFound(function);
@@ -187,14 +190,20 @@ bool COWOptsPass::optimizeBeginCOW(BeginCOWMutationInst *BCM) {
             // Don't immediately bail on a store instruction. Instead, remember
             // it and check if it interferes with any (potential) load.
             if (storeAddrsFound.insert(store->getDest())) {
+              LLVM_DEBUG(llvm::dbgs() << "Found store escape, record: ");
+              LLVM_DEBUG(inst->dump());
               storeAddrs.push_back(store->getDest());
               numStoresFound += 1;
             }
           } else {
+            LLVM_DEBUG(llvm::dbgs() << "Found non-store escape, bailing out: ");
+            LLVM_DEBUG(inst->dump());
             return false;
           }
         }
         if (inst->mayReadFromMemory()) {
+          LLVM_DEBUG(llvm::dbgs() << "Found a may read inst, record: ");
+          LLVM_DEBUG(inst->dump());
           potentialLoadInsts.push_back(inst);
           numLoadsFound += 1;
         }
@@ -225,8 +234,12 @@ bool COWOptsPass::optimizeBeginCOW(BeginCOWMutationInst *BCM) {
         return false;
       for (SILInstruction *load : potentialLoadInsts) {
         for (SILValue storeAddr : storeAddrs) {
-          if (!AA || AA->mayReadFromMemory(load, storeAddr))
+          if (!AA || AA->mayReadFromMemory(load, storeAddr)) {
+            LLVM_DEBUG(llvm::dbgs() << "Found a store address aliasing with a load:");
+            LLVM_DEBUG(load->dump());
+            LLVM_DEBUG(storeAddr->dump());
             return false;
+          }
         }
       }
     }

test/SILOptimizer/objectoutliner.sil

@@ -127,6 +127,24 @@ bb0:
   return %r : $()
 }
 
+// CHECK-LABEL: sil @outline_global_with_uncheckedrefcast : 
+// CHECK: global_value
+// CHECK: } // end sil function 'outline_global_with_uncheckedrefcast'
+sil @outline_global_with_uncheckedrefcast : $@convention(thin) () -> () {
+bb0:
+  %0 = integer_literal $Builtin.Word, 0
+  %1 = integer_literal $Builtin.Int64, 1
+  %4 = struct $Int64 (%1 : $Builtin.Int64)
+  %7 = alloc_ref [tail_elems $Int64 * %0 : $Builtin.Word] $Obj
+  %9 = ref_element_addr %7 : $Obj, #Obj.value
+  store %4 to %9 : $*Int64
+  %10 = unchecked_ref_cast %7 : $Obj to $Base
+  %11 = end_cow_mutation %10 : $Base
+  %12 = begin_dealloc_ref %11 : $Base of %7 : $Obj
+  dealloc_ref %12 : $Base
+  %r = tuple ()
+  return %r : $()
+}
 
 // CHECK-LABEL: sil @outline_global_tailelems
 // CHECK: [[G:%[0-9]+]] = global_value @outline_global_tailelemsTv_ : $Obj