Implement a few silcombine transformations for arrays

 - Useless existential_ref <-> class conversions.
 - mark_dependence_inst depending on uninteresting instructions.
 - release(init_existential_ref(x)) -> release(x) when hasOneUse(x)
 - Update COWArrayOpt to handle the new forms generated by this.

these aren't massive performance wins, but do shrink the size of SIL when
dealing with arrays.

Author: lattner

include/swift/SIL/SILInstruction.h

@@ -6000,6 +6000,13 @@ class MarkDependenceInst
   SILValue getValue() const { return Operands[Value].get(); }
   SILValue getBase() const { return Operands[Base].get(); }
 
+  void setValue(SILValue newVal) {
+    Operands[Value].set(newVal);
+  }
+  void setBase(SILValue newVal) {
+    Operands[Base].set(newVal);
+  }
+  
   ArrayRef<Operand> getAllOperands() const { return Operands.asArray(); }
   MutableArrayRef<Operand> getAllOperands() { return Operands.asArray(); }
 };

lib/SILOptimizer/LoopTransforms/COWArrayOpt.cpp

@@ -797,7 +797,7 @@ bool COWArrayOpt::checkSafeElementValueUses(UserOperList &ElementValueUsers) {
 static bool isArrayEltStore(StoreInst *SI) {
   SILValue Dest = stripAddressProjections(SI->getDest());
   if (auto *MD = dyn_cast<MarkDependenceInst>(Dest))
-    Dest = MD->getOperand(0);
+    Dest = MD->getValue();
 
   if (auto *PtrToAddr =
           dyn_cast<PointerToAddressInst>(stripAddressProjections(Dest)))
@@ -1095,17 +1095,21 @@ struct HoistableMakeMutable {
     DepInsts.push_back(StructExtractArrayAddr);
 
     // Check the base the array element address is dependent on.
-    auto *EnumArrayAddr = dyn_cast<EnumInst>(MarkDependence->getBase());
-    if (!EnumArrayAddr)
-      return false;
-    DepInsts.push_back(EnumArrayAddr);
-    auto *UncheckedRefCast =
-        dyn_cast<UncheckedRefCastInst>(EnumArrayAddr->getOperand());
-    if (!UncheckedRefCast)
-      return false;
-    DepInsts.push_back(UncheckedRefCast);
+    SILValue base = MarkDependence->getBase();
+
+    // We can optionally have an enum instruction here.
+    if (auto *EnumArrayAddr = dyn_cast<EnumInst>(base)) {
+      DepInsts.push_back(EnumArrayAddr);
+      base = EnumArrayAddr->getOperand();
+    }
+
+    // We can optionally have an unchecked cast.
+    if (auto *UncheckedRefCast = dyn_cast<UncheckedRefCastInst>(base)) {
+      DepInsts.push_back(UncheckedRefCast);
+      base = UncheckedRefCast->getOperand();
+    }
 
-    SILValue ArrayBuffer = stripValueProjections(UncheckedRefCast->getOperand(), DepInsts);
+    SILValue ArrayBuffer = stripValueProjections(base, DepInsts);
     auto *BaseLoad = dyn_cast<LoadInst>(ArrayBuffer);
     if (!BaseLoad ||  Loop->contains(BaseLoad->getOperand()->getParentBlock()))
       return false;

lib/SILOptimizer/SILCombiner/SILCombiner.h

@@ -240,6 +240,9 @@ class SILCombiner :
   SILInstruction *visitUnreachableInst(UnreachableInst *UI);
   SILInstruction *visitAllocRefDynamicInst(AllocRefDynamicInst *ARDI);
   SILInstruction *visitEnumInst(EnumInst *EI);
+      
+  SILInstruction *visitMarkDependenceInst(MarkDependenceInst *MDI);
+  SILInstruction *visitInitExistentialRefInst(InitExistentialRefInst *IER);
   SILInstruction *visitConvertFunctionInst(ConvertFunctionInst *CFI);
 
   /// Instruction visitor helpers.

lib/SILOptimizer/SILCombiner/SILCombinerMiscVisitors.cpp

@@ -1134,6 +1134,15 @@ SILInstruction *SILCombiner::visitStrongReleaseInst(StrongReleaseInst *SRI) {
       isa<ObjCMetatypeToObjectInst>(SRI->getOperand()))
     return eraseInstFromFunction(*SRI);
 
+  // Release of a classbound existential converted from a class is just a
+  // release of the class, squish the conversion.
+  if (auto ier = dyn_cast<InitExistentialRefInst>(SRI->getOperand()))
+    if (ier->hasOneUse()) {
+      SRI->setOperand(ier->getOperand());
+      eraseInstFromFunction(*ier);
+      return SRI;
+    }
+  
   return nullptr;
 }
 
@@ -1406,3 +1415,63 @@ SILInstruction *SILCombiner::visitEnumInst(EnumInst *EI) {
   return nullptr;
 }
 
+SILInstruction *SILCombiner::visitMarkDependenceInst(MarkDependenceInst *MDI) {
+  // Simplify the base operand of a MarkDependenceInst to eliminate unnecessary
+  // instructions that aren't adding value.
+  //
+  // Conversions to Optional.Some(x) often happen here, this isn't important
+  // for us, we can just depend on 'x' directly.
+  if (auto eiBase = dyn_cast<EnumInst>(MDI->getBase())) {
+    if (eiBase->hasOperand() && eiBase->hasOneUse()) {
+      MDI->setBase(eiBase->getOperand());
+      eraseInstFromFunction(*eiBase);
+      return MDI;
+    }
+  }
+  
+  // Conversions from a class to AnyObject also happen a lot, we can just depend
+  // on the class reference.
+  if (auto ier = dyn_cast<InitExistentialRefInst>(MDI->getBase())) {
+    MDI->setBase(ier->getOperand());
+    if (ier->use_empty())
+      eraseInstFromFunction(*ier);
+    return MDI;
+  }
+  
+  return nullptr;
+}
+
+
+SILInstruction *SILCombiner::
+visitInitExistentialRefInst(InitExistentialRefInst *IER) {
+  // Arrays in particular end up with chains of init/open existential refs,
+  // which convert back and forth between a class reference and an existential
+  // reference e.g. like this:
+  //
+  // %a = init_existential_ref %x : $_ContiguousArrayStorageBase :
+  //                                $_ContiguousArrayStorageBase, $_NSArrayCore
+  // %b = open_existential_ref %a : $_NSArrayCore to
+  //                                $@opened("EA85...") _NSArrayCore
+  //
+  // %c = init_existential_ref %b : $@opened("EA85...") _NSArrayCore :
+  //                                $@opened("EA85...") _NSArrayCore, $AnyObject
+  // we can simplify this by having %c initialize itself from the %x reference
+  // directly.
+  if (auto *ORE = dyn_cast<OpenExistentialRefInst>(IER->getOperand())) {
+    if (auto *IER2 = dyn_cast<InitExistentialRefInst>(ORE->getOperand())) {
+      
+      // We create a new instruction, instead of modifying the existing one
+      // in place, because we need the result type of "%c" but the operand list
+      // of "%a", and the number of dependent types could disagree.
+      return Builder.createInitExistentialRef(IER->getLoc(), IER->getType(),
+                                              IER2->getFormalConcreteType(),
+                                              IER2->getOperand(),
+                                              IER->getConformances());
+      
+    }
+  }
+  
+  return nullptr;
+}
+
+

test/SILOptimizer/pointer_conversion.swift

@@ -22,9 +22,9 @@ func get<T>() -> T
 public func testArray() {
   let array: [Int] = get()
   takesConstRawPointer(array)
-  // CHECK: [[OWNER:%.+]] = enum $Optional<AnyObject>, #Optional.some!enumelt.1,
-  // CHECK-NEXT: [[POINTER:%.+]] = struct $UnsafeRawPointer (
-  // CHECK-NEXT: [[DEP_POINTER:%.+]] = mark_dependence [[POINTER]] : $UnsafeRawPointer on [[OWNER]] : $Optional<AnyObject>
+  // CHECK: [[OWNER:%.+]] = unchecked_ref_cast
+  // CHECK: [[POINTER:%.+]] = struct $UnsafeRawPointer (
+  // CHECK-NEXT: [[DEP_POINTER:%.+]] = mark_dependence [[POINTER]] : $UnsafeRawPointer on [[OWNER]] : $_ContiguousArrayStorageBase
   // CHECK: [[FN:%.+]] = function_ref @takesConstRawPointer
   // CHECK-NEXT: apply [[FN]]([[DEP_POINTER]])
   // CHECK-NOT: release
@@ -38,9 +38,9 @@ public func testArray() {
 public func testArrayToOptional() {
   let array: [Int] = get()
   takesOptConstRawPointer(array)
-  // CHECK: [[OWNER:%.+]] = enum $Optional<AnyObject>, #Optional.some!enumelt.1,
-  // CHECK-NEXT: [[POINTER:%.+]] = struct $UnsafeRawPointer (
-  // CHECK-NEXT: [[DEP_POINTER:%.+]] = mark_dependence [[POINTER]] : $UnsafeRawPointer on [[OWNER]] : $Optional<AnyObject>
+  // CHECK: [[OWNER:%.+]] = unchecked_ref_cast
+  // CHECK: [[POINTER:%.+]] = struct $UnsafeRawPointer (
+  // CHECK-NEXT: [[DEP_POINTER:%.+]] = mark_dependence [[POINTER]] : $UnsafeRawPointer on [[OWNER]] : $_ContiguousArrayStorageBase
   // CHECK-NEXT: [[OPT_POINTER:%.+]] = enum $Optional<UnsafeRawPointer>, #Optional.some!enumelt.1, [[DEP_POINTER]]
   // CHECK: [[FN:%.+]] = function_ref @takesOptConstRawPointer
   // CHECK-NEXT: apply [[FN]]([[OPT_POINTER]])
@@ -55,9 +55,8 @@ public func testArrayToOptional() {
 public func testMutableArray() {
   var array: [Int] = get()
   takesMutableRawPointer(&array)
-  // CHECK: [[OWNER:%.+]] = enum $Optional<AnyObject>, #Optional.some!enumelt.1,
-  // CHECK-NEXT: [[POINTER:%.+]] = struct $UnsafeMutableRawPointer (
-  // CHECK-NEXT: [[DEP_POINTER:%.+]] = mark_dependence [[POINTER]] : $UnsafeMutableRawPointer on [[OWNER]] : $Optional<AnyObject>
+  // CHECK: [[POINTER:%.+]] = struct $UnsafeMutableRawPointer (
+  // CHECK-NEXT: [[DEP_POINTER:%.+]] = mark_dependence [[POINTER]] : $UnsafeMutableRawPointer on {{.*}} : $_ContiguousArrayStorageBase
   // CHECK: [[FN:%.+]] = function_ref @takesMutableRawPointer
   // CHECK-NEXT: apply [[FN]]([[DEP_POINTER]])
   // CHECK-NOT: release
@@ -72,9 +71,8 @@ public func testMutableArray() {
 public func testMutableArrayToOptional() {
   var array: [Int] = get()
   takesOptMutableRawPointer(&array)
-  // CHECK: [[OWNER:%.+]] = enum $Optional<AnyObject>, #Optional.some!enumelt.1,
-  // CHECK-NEXT: [[POINTER:%.+]] = struct $UnsafeMutableRawPointer (
-  // CHECK-NEXT: [[DEP_POINTER:%.+]] = mark_dependence [[POINTER]] : $UnsafeMutableRawPointer on [[OWNER]] : $Optional<AnyObject>
+  // CHECK: [[POINTER:%.+]] = struct $UnsafeMutableRawPointer (
+  // CHECK-NEXT: [[DEP_POINTER:%.+]] = mark_dependence [[POINTER]] : $UnsafeMutableRawPointer on {{.*}} : $_ContiguousArrayStorageBase
   // CHECK-NEXT: [[OPT_POINTER:%.+]] = enum $Optional<UnsafeMutableRawPointer>, #Optional.some!enumelt.1, [[DEP_POINTER]]
   // CHECK: [[FN:%.+]] = function_ref @takesOptMutableRawPointer
   // CHECK-NEXT: apply [[FN]]([[OPT_POINTER]])
@@ -112,3 +110,28 @@ public func testOptionalArray() {
   // CHECK-NEXT: [[NO_OWNER:%.+]] = enum $Optional<AnyObject>, #Optional.none!enumelt
   // CHECK-NEXT: br [[CALL_BRANCH]]([[NO_POINTER]] : $Optional<UnsafeRawPointer>, [[NO_OWNER]] : $Optional<AnyObject>)
 } // CHECK: end sil function '_T018pointer_conversion17testOptionalArrayyyF'
+
+
+// CHECK-LABEL: sil @_T018pointer_conversion21arrayLiteralPromotionyyF
+public func arrayLiteralPromotion() {
+  takesConstRawPointer([41,42,43,44])
+  
+  // Stack allocate the array.
+  // CHECK: alloc_ref [stack] [tail_elems $Int * {{.*}} : $Builtin.Word] $_ContiguousArrayStorage<Int>
+  
+  // Store the elements.
+  // CHECK: [[ELT:%.+]] = integer_literal $Builtin.Int{{.*}}, 41
+  // CHECK: [[ELT:%.+]] = integer_literal $Builtin.Int{{.*}}, 42
+  // CHECK: [[ELT:%.+]] = integer_literal $Builtin.Int{{.*}}, 43
+  // CHECK: [[ELT:%.+]] = integer_literal $Builtin.Int{{.*}}, 44
+  
+  // Call the function.
+  // CHECK: [[PTR:%.+]] = mark_dependence
+
+  // CHECK: [[FN:%.+]] = function_ref @takesConstRawPointer
+  // CHECK: apply [[FN]]([[PTR]])
+  
+  // Release the heap value.
+  // CHECK: strong_release
+}
+

test/SILOptimizer/sil_combine.sil

@@ -2083,6 +2083,19 @@ bb0(%0 : $B, %1 : $@sil_unowned B, %2 : $AnyObject, %3: $@sil_unmanaged AnyObjec
   return %9999 : $(B, @sil_unowned B, AnyObject, @sil_unmanaged AnyObject)
 }
 
+// CHECK-LABEL: sil @collapse_init_open_init_ref_cast
+// CHECK:       bb0([[Ref:%.*]]: $MyClass):
+// CHECK-NEXT:     init_existential_ref
+// CHECK-NEXT:     return
+sil @collapse_init_open_init_ref_cast : $@convention(thin) (MyClass) -> (AnyObject) {
+bb0(%0: $MyClass):
+  %1 = init_existential_ref %0 : $MyClass : $MyClass, $AnyObject
+  %2 = open_existential_ref %1 : $AnyObject to $@opened("2CAE06CE-5F10-11E4-AF13-C82A1428F987") AnyObject
+  %3 = init_existential_ref %2 : $@opened("2CAE06CE-5F10-11E4-AF13-C82A1428F987") AnyObject : $@opened("2CAE06CE-5F10-11E4-AF13-C82A1428F987") AnyObject, $AnyObject
+  return %3 : $AnyObject
+}
+
+
 // CHECK-LABEL: sil @collapse_existential_pack_unpack_unchecked_ref_cast
 // CHECK:       bb0([[Ref:%.*]]: $MyClass):
 // CHECK-NOT:     init_existential_ref
@@ -3429,3 +3442,22 @@ bb1(%4 : $Builtin.Int32):
 bb2(%5 : $MyErrorType):
   throw %5 : $MyErrorType
 }
+
+// CHECK-LABEL: sil @mark_dependence_base
+// CHECK: bb0(
+// CHECK-NOT: init_existential_ref
+// CHECK-NOT: enum
+// CHECK-NEXT: mark_dependence
+// CHECK-NEXT: load
+// CHECK: return
+sil @mark_dependence_base : $@convention(thin) (@inout Builtin.Int64, @owned B) -> Builtin.Int64 {
+bb0(%0 : $*Builtin.Int64, %1 : $B):
+  %x = init_existential_ref %1 : $B : $B, $AnyObject
+  %2 = enum $Optional<AnyObject>, #Optional.some!enumelt.1, %x : $AnyObject
+  %3 = mark_dependence %0 : $*Builtin.Int64 on %2 : $Optional<AnyObject>
+  %4 = load %3 : $*Builtin.Int64
+  return %4 : $Builtin.Int64
+}
+
+
+