Merge pull request swiftlang#3286 from eeckstein/escape-analysis

lib/SILOptimizer/Analysis/EscapeAnalysis.cpp

@@ -17,6 +17,7 @@
 #include "swift/SILOptimizer/Analysis/ValueTracking.h"
 #include "swift/SILOptimizer/PassManager/PassManager.h"
 #include "swift/SIL/SILArgument.h"
+#include "swift/SIL/DebugUtils.h"
 #include "llvm/Support/GraphWriter.h"
 #include "llvm/Support/raw_ostream.h"
 
@@ -30,13 +31,23 @@ static bool isProjection(ValueBase *V) {
     case ValueKind::TupleElementAddrInst:
     case ValueKind::UncheckedTakeEnumDataAddrInst:
     case ValueKind::StructExtractInst:
-    case ValueKind::TupleExtractInst:
     case ValueKind::UncheckedEnumDataInst:
     case ValueKind::MarkDependenceInst:
     case ValueKind::PointerToAddressInst:
     case ValueKind::AddressToPointerInst:
     case ValueKind::InitEnumDataAddrInst:
       return true;
+    case ValueKind::TupleExtractInst: {
+      auto *TEI = cast<TupleExtractInst>(V);
+      // Special handling for extracting the pointer-result from an
+      // array construction. We handle this like a ref_element_addr
+      // rather than a projection. See the handling of tuple_extract
+      // in analyzeInstruction().
+      if (TEI->getFieldNo() == 1 &&
+          ArraySemanticsCall(TEI->getOperand(), "array.uninitialized", false))
+        return false;
+      return true;
+    }
     default:
       return false;
   }
@@ -1095,6 +1106,15 @@ void EscapeAnalysis::buildConnectionGraph(FunctionInfo *FInfo,
         FInfo->Graph.F->getName() << '\n');
 }
 
+/// Returns true if all uses of \p I are tuple_extract instructions.
+static bool onlyUsedInTupleExtract(SILInstruction *I) {
+  for (Operand *Use : getNonDebugUses(I)) {
+    if (!isa<TupleExtractInst>(Use->getUser()))
+      return false;
+  }
+  return true;
+}
+
 void EscapeAnalysis::analyzeInstruction(SILInstruction *I,
                                         FunctionInfo *FInfo,
                                         FunctionOrder &BottomUpOrder,
@@ -1113,13 +1133,20 @@ void EscapeAnalysis::analyzeInstruction(SILInstruction *I,
         // These array semantics calls do not capture anything.
         return;
       case ArrayCallKind::kArrayUninitialized:
-        // array.uninitialized may have a first argument which is the
-        // allocated array buffer. The call is like a struct(buffer)
-        // instruction.
-        if (CGNode *BufferNode = ConGraph->getNode(FAS.getArgument(0), this)) {
-          ConGraph->defer(ConGraph->getNode(I, this), BufferNode);
+        // Check if the result is used in the usual way: extracting the
+        // array and the element pointer with tuple_extract.
+        if (onlyUsedInTupleExtract(I)) {
+          // array.uninitialized may have a first argument which is the
+          // allocated array buffer. The call is like a struct(buffer)
+          // instruction.
+          if (CGNode *BufferNode = ConGraph->getNode(FAS.getArgument(0), this)) {
+            CGNode *ArrayNode = ConGraph->getNode(I, this);
+            CGNode *ArrayContent = ConGraph->getContentNode(ArrayNode);
+            ConGraph->defer(ArrayContent, BufferNode);
+          }
+          return;
         }
-        return;
+        break;
       case ArrayCallKind::kGetArrayOwner:
         if (CGNode *BufferNode = ConGraph->getNode(ASC.getSelf(), this)) {
           ConGraph->defer(ConGraph->getNode(I, this), BufferNode);
@@ -1388,6 +1415,21 @@ void EscapeAnalysis::analyzeInstruction(SILInstruction *I,
       }
       return;
     }
+    case ValueKind::TupleExtractInst: {
+      // This is a tuple_extract which extracts the second result of an
+      // array.uninitialized call. The first result is the array itself.
+      // The second result (which is a pointer to the array elements) must be
+      // the content node of the first result. It's just like a ref_element_addr
+      // instruction.
+      auto *TEI = cast<TupleExtractInst>(I);
+      assert(TEI->getFieldNo() == 1 &&
+          ArraySemanticsCall(TEI->getOperand(), "array.uninitialized", false)
+             && "tuple_extract should be handled as projection");
+      CGNode *ArrayNode = ConGraph->getNode(TEI->getOperand(), this);
+      CGNode *ArrayElements = ConGraph->getContentNode(ArrayNode);
+      ConGraph->setNode(I, ArrayElements);
+      return;
+    }
     case ValueKind::UncheckedRefCastInst:
     case ValueKind::ConvertFunctionInst:
     case ValueKind::UpcastInst:

test/SILOptimizer/escape_analysis.sil

@@ -1239,6 +1239,28 @@ bb(%0 : $*Array<X>, %1 : $@callee_owned (@inout X) -> (@out (), @error ErrorType
   return %r : $()
 }
 
+// CHECK-LABEL: CG of arraysemantics_createUninitialized
+// CHECK-NEXT:    Arg %0 Esc: A, Succ: 
+// CHECK-NEXT:    Val %2 Esc: R, Succ: (%4.2)
+// CHECK-NEXT:    Val %4 Esc: R, Succ: (%4.1)
+// CHECK-NEXT:    Con %4.1 Esc: R, Succ: %2
+// CHECK-NEXT:    Con %4.2 Esc: R, Succ: %0
+// CHECK-NEXT:    Ret  Esc: R, Succ: %4
+// CHECK-NEXT:  End
+sil @arraysemantics_createUninitialized : $@convention(thin) (@owned X) -> @owned Array<X> {
+bb0(%0 : $X):
+  %1 = function_ref @swift_bufferAllocate : $@convention(thin) () -> @owned AnyObject
+  %2 = apply %1() : $@convention(thin) () -> @owned AnyObject
+  %3 = function_ref @createUninitialized : $@convention(method) (@owned AnyObject) -> (@owned Array<X>, UnsafeMutablePointer<X>)
+  %4 = apply %3(%2) : $@convention(method) (@owned AnyObject) -> (@owned Array<X>, UnsafeMutablePointer<X>)
+  %5 = tuple_extract %4 : $(Array<X>, UnsafeMutablePointer<X>), 0
+  %6 = tuple_extract %4 : $(Array<X>, UnsafeMutablePointer<X>), 1
+  %7 = struct_extract %6 : $UnsafeMutablePointer<X>, #UnsafeMutablePointer._rawValue
+  %8 = pointer_to_address %7 : $Builtin.RawPointer to $*X
+  store %0 to %8 : $*X
+  return %5 : $Array<X>
+}
+
 sil [_semantics "array.withUnsafeMutableBufferPointer"] @withUnsafeMutableBufferPointer : $@convention(method) (@owned @callee_owned (@inout X) -> (@out (), @error ErrorType), @inout Array<X>) -> (@out (), @error ErrorType)
 sil [_semantics "array.props.isNativeTypeChecked"] @is_native_type_checked : $@convention(method) (@guaranteed Array<X>) -> Bool
 sil [_semantics "array.check_subscript"] @check_subscript : $@convention(method) (Int32, Bool, @guaranteed Array<X>) -> ()
@@ -1251,6 +1273,10 @@ sil [_semantics "array.get_capacity"] @get_capacity : $@convention(method) (@gua
 
 sil [_semantics "pair_no_escaping_closure"] @unsafeWithNotEscapedSelfPointerPair : $@convention(method) (@owned X, @owned @callee_owned (X, X) -> (@out X, @error ErrorType), @guaranteed X) -> (@out X, @error ErrorType)
 sil [_semantics "self_no_escaping_closure"] @unsafeWithNotEscapedSelfPointer: $@convention(method) (@owned @callee_owned (X, X) -> (@out X, @error ErrorType), @guaranteed X) -> (@out X, @error ErrorType)
+sil [_semantics "array.uninitialized"] @createUninitialized : $@convention(method) (@owned AnyObject) -> (@owned Array<X>, UnsafeMutablePointer<X>)
+
+// A simplified version of swift_bufferAllocate
+sil @swift_bufferAllocate : $@convention(thin) () -> @owned AnyObject
 
 // CHECK-LABEL: CG of semantics_pair_no_escaping_closure
 // CHECK-NEXT:   Arg %0 Esc: A, Succ:

test/SILOptimizer/stack_promotion_escaping.swift

@@ -0,0 +1,25 @@
+// RUN: %target-swift-frontend -parse-as-library -O -module-name=test %s -emit-sil | FileCheck %s
+
+final class Item {}
+
+final public class Escaper {
+  var myItem: Item = Item()
+
+  @inline(never)
+  func update(items: [Item]) {
+    myItem = items[0]
+  }
+
+// CHECK-LABEL: sil [noinline] @_TFC4test7Escaper15badStuffHappensfT_T_ : $@convention(method) (@guaranteed Escaper) -> () {
+// CHECK: %2 = alloc_ref $Item
+// CHECK: function_ref @swift_bufferAllocateOnStack
+// CHECK: return
+  @inline(never)
+  public func badStuffHappens() {
+    // Check that 'item' is not stack promoted, because it escapes to myItem.
+    let item = Item()
+    // On the other hand, the array buffer of the array literal should be stack promoted.
+    update(items:[item])
+  }
+}
+