Merge pull request swiftlang#5140 from eeckstein/silcombine-alloc-ref-dynamic

SILCombine: handle upcasts when converting from alloc_ref_dynamic to alloc_ref

Author: eeckstein

lib/SILOptimizer/SILCombiner/SILCombinerMiscVisitors.cpp

@@ -1238,34 +1238,44 @@ visitAllocRefDynamicInst(AllocRefDynamicInst *ARDI) {
   // ->
   // alloc_ref X
   Builder.setCurrentDebugScope(ARDI->getDebugScope());
-  if (MetatypeInst *MI = dyn_cast<MetatypeInst>(ARDI->getOperand())) {
+
+  SILValue MDVal = ARDI->getOperand();
+  if (auto *UC = dyn_cast<UpcastInst>(MDVal))
+    MDVal = UC->getOperand();
+
+  SILInstruction *NewInst = nullptr;
+  if (MetatypeInst *MI = dyn_cast<MetatypeInst>(MDVal)) {
     auto &Mod = ARDI->getModule();
     auto SILInstanceTy = MI->getType().getMetatypeInstanceType(Mod);
-    auto *ARI = Builder.createAllocRef(ARDI->getLoc(), SILInstanceTy,
-                                       ARDI->isObjC(), false);
-    return ARI;
-  }
 
-  // checked_cast_br [exact] $Y.Type to $X.Type, bbSuccess, bbFailure
-  // ...
-  // bbSuccess(%T: $X.Type)
-  // alloc_ref_dynamic %T : $X.Type, $X
-  // ->
-  // alloc_ref $X
-  if (isa<SILArgument>(ARDI->getOperand())) {
+    NewInst = Builder.createAllocRef(ARDI->getLoc(), SILInstanceTy,
+                                     ARDI->isObjC(), false);
+
+  } else if (isa<SILArgument>(MDVal)) {
+
+    // checked_cast_br [exact] $Y.Type to $X.Type, bbSuccess, bbFailure
+    // ...
+    // bbSuccess(%T: $X.Type)
+    // alloc_ref_dynamic %T : $X.Type, $X
+    // ->
+    // alloc_ref $X
     auto *PredBB = ARDI->getParent()->getSinglePredecessor();
     if (!PredBB)
       return nullptr;
     auto *CCBI = dyn_cast<CheckedCastBranchInst>(PredBB->getTerminator());
     if (CCBI && CCBI->isExact() && ARDI->getParent() == CCBI->getSuccessBB()) {
       auto &Mod = ARDI->getModule();
       auto SILInstanceTy = CCBI->getCastType().getMetatypeInstanceType(Mod);
-      auto *ARI = Builder.createAllocRef(ARDI->getLoc(), SILInstanceTy,
+      NewInst = Builder.createAllocRef(ARDI->getLoc(), SILInstanceTy,
                                          ARDI->isObjC(), false);
-      return ARI;
     }
   }
-  return nullptr;
+  if (NewInst && NewInst->getType() != ARDI->getType()) {
+    // In case the argument was an upcast of the metatype, we have to upcast the
+    // resulting reference.
+    NewInst = Builder.createUpcast(ARDI->getLoc(), NewInst, ARDI->getType());
+  }
+  return NewInst;
 }
 
 SILInstruction *SILCombiner::visitEnumInst(EnumInst *EI) {

test/SILOptimizer/sil_combine.sil

@@ -2256,6 +2256,22 @@ sil @alloc_ref_dynamic_with_metatype : $() -> () {
   return %4 : $()
 }
 
+// CHECK-LABEL: sil @alloc_ref_dynamic_with_upcast_metatype
+// CHECK: bb0
+// CHECK-NOT: alloc_ref_dynamic
+// CHECK-NEXT: [[R:%[0-9]+]] = alloc_ref $E
+// CHECK-NEXT: [[C:%[0-9]+]] = upcast [[R]] : $E to $B
+// CHECK-NEXT: strong_release [[C]]
+// CHECK: return
+sil @alloc_ref_dynamic_with_upcast_metatype : $() -> () {
+  %1 = metatype $@thick E.Type
+  %2 = upcast %1 : $@thick E.Type to $@thick B.Type
+  %3 = alloc_ref_dynamic %2 : $@thick B.Type, $B
+  strong_release %3 : $B
+  %4 = tuple()
+  return %4 : $()
+}
+
 // CHECK-LABEL: @alloc_ref_dynamic_after_successful_checked_cast_br
 // CHECK: checked_cast_br
 // CHECK: bb1
@@ -2279,6 +2295,32 @@ bb3 (%10: $Builtin.Int32):
   return %10 : $Builtin.Int32
 }
 
+// CHECK-LABEL: @alloc_ref_dynamic_upcast_after_successful_checked_cast_br
+// CHECK: checked_cast_br
+// CHECK: bb1
+// CHECK-NOT: alloc_ref_dynamic
+// CHECK:      [[R:%[0-9]+]] = alloc_ref $E
+// CHECK-NEXT: [[C:%[0-9]+]] = upcast [[R]] : $E to $B
+// CHECK-NEXT: strong_release [[C]]
+sil @alloc_ref_dynamic_upcast_after_successful_checked_cast_br : $(@thick B.Type) -> Builtin.Int32 {
+bb0(%1 : $@thick B.Type):
+  checked_cast_br [exact] %1 : $@thick B.Type to $@thick E.Type, bb1, bb2
+
+bb1(%2 : $@thick E.Type):
+  %3 = upcast %2 : $@thick E.Type to $@thick B.Type
+  %4 = alloc_ref_dynamic %3 : $@thick B.Type, $B
+  strong_release %4 : $B
+  %5 = integer_literal $Builtin.Int32, 1
+  br bb3 (%5 : $Builtin.Int32)
+
+bb2:
+  %6 = integer_literal $Builtin.Int32, 2
+  br bb3 (%6 : $Builtin.Int32)
+
+bb3 (%10: $Builtin.Int32):
+  return %10 : $Builtin.Int32
+}
+
 // CHECK-LABEL: sil @delete_dead_alloc_stack
 // CHECK: bb0
 // CHECK-NEXT: tuple