[Constant Evaluator] Add support for thin_to_thick_function SIL instruction,

and fix bugs in the evaluator in the implementation of array.append, and in
loading/linking external function.

Author: ravikandhadai

include/swift/SILOptimizer/Utils/ConstExpr.h

@@ -207,6 +207,9 @@ class ConstExprStepEvaluator {
   const SmallPtrSetImpl<SILFunction *> &getFuncsCalledDuringEvaluation() {
     return evaluator.getFuncsCalledDuringEvaluation();
   }
+
+  /// Dump the internal state to standard error for debugging.
+  void dumpState();
 };
 
 bool isKnownConstantEvaluableFunction(SILFunction *fun);

lib/SILOptimizer/Utils/ConstExpr.cpp

@@ -55,7 +55,10 @@ enum class WellKnownFunction {
   // String.percentEscapedString.getter
   StringEscapePercent,
   // _assertionFailure(_: StaticString, _: StaticString, file: StaticString,...)
-  AssertionFailure
+  AssertionFailure,
+  // A function taking one argument that prints the symbolic value of the
+  // argument during constant evaluation. This must only be used for debugging.
+  DebugPrint
 };
 
 static llvm::Optional<WellKnownFunction> classifyFunction(SILFunction *fn) {
@@ -80,6 +83,12 @@ static llvm::Optional<WellKnownFunction> classifyFunction(SILFunction *fn) {
     return WellKnownFunction::StringEscapePercent;
   if (fn->hasSemanticsAttrThatStartsWith("programtermination_point"))
     return WellKnownFunction::AssertionFailure;
+  // A call to a function with the following semantics annotation will be
+  // considered as a DebugPrint operation. The evaluator will print the value
+  // of the single argument passed to this function call to the standard error.
+  // This functionality must be used only for debugging the evaluator.
+  if (fn->hasSemanticsAttrThatStartsWith("constant_evaluator_debug_print"))
+    return WellKnownFunction::DebugPrint;
   return None;
 }
 
@@ -222,6 +231,13 @@ class ConstExprFunctionState {
   llvm::Optional<SymbolicValue>
   computeWellKnownCallResult(ApplyInst *apply, WellKnownFunction callee);
 
+  /// Evaluate a closure creation instruction which is either a partial_apply
+  /// instruction or a thin_to_think_function instruction. On success, this
+  /// function will bind the \c closureInst parameter to its symbolic value.
+  /// On failure, it returns the unknown symbolic value that captures the error.
+  llvm::Optional<SymbolicValue>
+  evaluateClosureCreation(SingleValueInstruction *closureInst);
+
   SymbolicValue getSingleWriterAddressValue(SILValue addr);
   SymbolicValue getConstAddrAndLoadResult(SILValue addr);
   SymbolicValue loadAddrValue(SILValue addr, SymbolicValue addrVal);
@@ -883,36 +899,19 @@ ConstExprFunctionState::computeWellKnownCallResult(ApplyInst *apply,
            conventions.getNumIndirectSILResults() == 0 &&
            "unexpected Array.append(_:) signature");
     // Get the element to be appended which is passed indirectly (@in).
-    SymbolicValue elementAddress = getConstantValue(apply->getOperand(1));
-    if (!elementAddress.isConstant())
-      return elementAddress;
-
-    auto invalidOperand = [&]() {
+    SymbolicValue element = getConstAddrAndLoadResult(apply->getOperand(1));
+    if (!element.isConstant())
+      return element;
+
+    // Get the array value. The array is passed @inout and could be a property
+    // of a struct.
+    SILValue arrayAddress = apply->getOperand(2);
+    SymbolicValue arrayValue = getConstAddrAndLoadResult(arrayAddress);
+    if (!arrayValue.isConstant())
+      return arrayValue;
+    if (arrayValue.getKind() != SymbolicValue::Array) {
       return getUnknown(evaluator, (SILInstruction *)apply,
                         UnknownReason::InvalidOperandValue);
-    };
-    if (elementAddress.getKind() != SymbolicValue::Address) {
-      // TODO: store the operand number in the error message here.
-      return invalidOperand();
-    }
-
-    SmallVector<unsigned, 4> elementAP;
-    SymbolicValue element =
-        elementAddress.getAddressValue(elementAP)->getValue();
-
-    // Get the array value. The array is passed @inout.
-    SymbolicValue arrayAddress = getConstantValue(apply->getOperand(2));
-    if (!arrayAddress.isConstant())
-      return arrayAddress;
-    if (arrayAddress.getKind() != SymbolicValue::Address)
-      return invalidOperand();
-
-    SmallVector<unsigned, 4> arrayAP;
-    SymbolicValueMemoryObject *arrayMemoryObject =
-        arrayAddress.getAddressValue(arrayAP);
-    SymbolicValue arrayValue = arrayMemoryObject->getValue();
-    if (arrayValue.getKind() != SymbolicValue::Array) {
-      return invalidOperand();
     }
 
     // Create a new array storage by appending the \c element to the existing
@@ -930,7 +929,7 @@ ConstExprFunctionState::computeWellKnownCallResult(ApplyInst *apply,
         newElements, elementType, allocator);
     SymbolicValue newArray = SymbolicValue::getArray(arrayValue.getArrayType(),
                                                      newStorage, allocator);
-    arrayMemoryObject->setIndexedElement(arrayAP, newArray, allocator);
+    computeFSStore(newArray, arrayAddress);
     return None;
   }
   case WellKnownFunction::StringInitEmpty: { // String.init()
@@ -1056,6 +1055,21 @@ ConstExprFunctionState::computeWellKnownCallResult(ApplyInst *apply,
     setValue(apply, resultVal);
     return None;
   }
+  case WellKnownFunction::DebugPrint: {
+    assert(apply->getNumArguments() == 1 &&
+           "debug_print function must take exactly one argument");
+    SILValue argument = apply->getArgument(0);
+    SymbolicValue argValue = getConstantValue(argument);
+    llvm::errs() << "Debug print output ";
+    argValue.print(llvm::errs());
+    if (argValue.getKind() != SymbolicValue::Address)
+      return None;
+
+    llvm::errs() << "\n  Addressed Memory Object: ";
+    SymbolicValueMemoryObject *memObj = argValue.getAddressValueMemoryObject();
+    memObj->getValue().print(llvm::errs());
+    return None;
+  }
   }
   llvm_unreachable("unhandled WellKnownFunction");
 }
@@ -1092,10 +1106,11 @@ ConstExprFunctionState::computeCallResult(ApplyInst *apply) {
   }
 
   // If we reached an external function that hasn't been deserialized yet, make
-  // sure to pull it in so we can see its body.  If that fails, then we can't
-  // analyze the function.
+  // sure to pull it in so we can see its body. If that fails, then we can't
+  // analyze the function. Note: pull in everything referenced from another
+  // module in case some referenced functions have non-public linkage.
   if (callee->isExternalDeclaration()) {
-    callee->getModule().loadFunction(callee);
+    apply->getModule().linkFunction(callee, SILModule::LinkingMode::LinkAll);
     if (callee->isExternalDeclaration())
       return computeOpaqueCallResult(apply, callee);
   }
@@ -1547,6 +1562,43 @@ ConstExprFunctionState::computeFSStore(SymbolicValue storedCst, SILValue dest) {
   return None;
 }
 
+llvm::Optional<SymbolicValue> ConstExprFunctionState::evaluateClosureCreation(
+    SingleValueInstruction *closureInst) {
+  assert(isa<PartialApplyInst>(closureInst) ||
+         isa<ThinToThickFunctionInst>(closureInst));
+  SILValue calleeOperand = closureInst->getOperand(0);
+  SymbolicValue calleeValue = getConstantValue(calleeOperand);
+  if (!calleeValue.isConstant())
+    return calleeValue;
+  if (calleeValue.getKind() != SymbolicValue::Function) {
+    return getUnknown(evaluator, (SILInstruction *)closureInst,
+                      UnknownReason::InvalidOperandValue);
+  }
+
+  SILFunction *target = calleeValue.getFunctionValue();
+  assert(target != nullptr);
+
+  SmallVector<SymbolicClosureArgument, 4> captures;
+
+  // If this is a partial-apply instruction, arguments to this partial-apply
+  // instruction are the captures of the closure.
+  if (PartialApplyInst *papply = dyn_cast<PartialApplyInst>(closureInst)) {
+    for (SILValue capturedSILValue : papply->getArguments()) {
+      SymbolicValue capturedSymbolicValue = getConstantValue(capturedSILValue);
+      if (!capturedSymbolicValue.isConstant()) {
+        captures.push_back({capturedSILValue, None});
+        continue;
+      }
+      captures.push_back({capturedSILValue, capturedSymbolicValue});
+    }
+  }
+
+  auto closureVal =
+      SymbolicValue::makeClosure(target, captures, evaluator.getAllocator());
+  setValue(closureInst, closureVal);
+  return None;
+}
+
 /// Evaluate the specified instruction in a flow sensitive way, for use by
 /// the constexpr function evaluator.  This does not handle control flow
 /// statements.  This returns None on success, and an Unknown SymbolicValue with
@@ -1630,34 +1682,8 @@ ConstExprFunctionState::evaluateFlowSensitive(SILInstruction *inst) {
                           injectEnumInst->getOperand());
   }
 
-  if (auto *papply = dyn_cast<PartialApplyInst>(inst)) {
-    SILValue calleeOperand = papply->getOperand(0);
-    SymbolicValue calleeValue = getConstantValue(calleeOperand);
-    if (!calleeValue.isConstant())
-      return calleeValue;
-    if (calleeValue.getKind() != SymbolicValue::Function) {
-      return getUnknown(evaluator, (SILInstruction *)papply,
-                        UnknownReason::InvalidOperandValue);
-    }
-
-    SILFunction *target = calleeValue.getFunctionValue();
-    assert(target != nullptr);
-
-    // Arguments to this partial-apply instruction are the captures of the
-    // closure.
-    SmallVector<SymbolicClosureArgument, 4> captures;
-    for (SILValue argument : papply->getArguments()) {
-      SymbolicValue argumentValue = getConstantValue(argument);
-      if (!argumentValue.isConstant()) {
-        captures.push_back({ argument, None });
-        continue;
-      }
-      captures.push_back({ argument, argumentValue });
-    }
-    auto closureVal = SymbolicValue::makeClosure(target, captures,
-                                                 evaluator.getAllocator());
-    setValue(papply, closureVal);
-    return None;
+  if (isa<PartialApplyInst>(inst) || isa<ThinToThickFunctionInst>(inst)) {
+    return evaluateClosureCreation(cast<SingleValueInstruction>(inst));
   }
 
   // If the instruction produces a result, try computing it, and fail if the
@@ -2073,6 +2099,8 @@ ConstExprStepEvaluator::lookupConstValue(SILValue value) {
   return res;
 }
 
+void ConstExprStepEvaluator::dumpState() { internalState->dump(); }
+
 bool swift::isKnownConstantEvaluableFunction(SILFunction *fun) {
   return classifyFunction(fun).hasValue();
 }

test/SILOptimizer/constant_evaluable_subset_test.swift

@@ -785,6 +785,24 @@ func interpretArrayAppendNonEmpty() -> [String] {
   return testArrayAppendNonEmpty("mkdir")
 }
 
+struct StructContaningArray {
+  var array: [Int]
+}
+
+// CHECK-LABEL: @testArrayFieldAppend
+// CHECK-NOT: error:
+@_semantics("constant_evaluable")
+func testArrayFieldAppend(_ x: Int) -> StructContaningArray {
+  var s = StructContaningArray(array: [])
+  s.array.append(x)
+  return s
+}
+
+@_semantics("test_driver")
+func interpretArrayFieldAppend() -> StructContaningArray {
+  return testArrayFieldAppend(0)
+}
+
 // CHECK-LABEL: @testClosureInit
 // CHECK-NOT: error:
 @_semantics("constant_evaluable")
@@ -833,3 +851,44 @@ func testAutoClosure(_ x: @escaping @autoclosure () -> Int) -> () -> Int {
 func interpretAutoClosure(_ x: Int) -> () -> Int {
   return testAutoClosure(x)
 }
+
+// Test thin-to-thick function conversion.
+
+func someFunction(_ x: Int) -> Int {
+  return x + 1
+}
+
+// CHECK-LABEL: @testThinToThick
+// CHECK-NOT: error:
+@_semantics("constant_evaluable")
+func testThinToThick() -> (Int) -> Int {
+  return someFunction
+}
+
+@_semantics("test_driver")
+func interpretThinToThick() -> (Int) -> Int {
+  return testThinToThick()
+}
+
+// Test closures and arrays combination.
+
+// CHECK-LABEL: @testArrayOfClosures
+// CHECK-NOT: error:
+@_semantics("constant_evaluable")
+func testArrayOfClosures(_ byte: @escaping () -> Int) -> [(Int) -> Int] {
+  var closureArray: [(Int) -> Int] = []
+  // Append a simple closure.
+  closureArray.append({ arg in
+    return 0
+  })
+  // Append a closure that does computation.
+  closureArray.append({ arg in
+    return byte() + arg
+  })
+  return closureArray
+}
+
+@_semantics("test_driver")
+func interpretArrayOfClosures() -> [(Int) -> Int] {
+  return testArrayOfClosures({ 10 })
+}

test/SILOptimizer/constant_evaluator_test.sil

@@ -1336,6 +1336,41 @@ bb0:
   // CHECK: agg: 1 elt: int: 14
   // CHECK: agg: 1 elt: int: 100
 
+struct StructContainingArray {
+  var array: [Int64]
+}
+
+// CHECK-LABEL: @interpretArrayAppendViaStructElementAddr
+sil [ossa] @interpretArrayAppendViaStructElementAddr : $@convention(thin) () -> @owned StructContainingArray {
+bb0:
+  %3 = metatype $@thin Array<Int64>.Type
+  // function_ref Array.init()
+  %4 = function_ref @$sS2ayxGycfC : $@convention(method) <τ_0_0> (@thin Array<τ_0_0>.Type) -> @owned Array<τ_0_0>
+  %5 = apply %4<Int64>(%3) : $@convention(method) <τ_0_0> (@thin Array<τ_0_0>.Type) -> @owned Array<τ_0_0>
+  %6 = struct $StructContainingArray (%5 : $Array<Int64>)
+
+  %7 = alloc_stack $StructContainingArray, var, name "s"
+  store %6 to [init] %7 : $*StructContainingArray
+  %8 = struct_element_addr %7 : $*StructContainingArray, #StructContainingArray.array
+
+  %9 = integer_literal $Builtin.Int64, 105
+  %10 = struct $Int64 (%9 : $Builtin.Int64)
+  %11 = alloc_stack $Int64
+  store %10 to [trivial] %11 : $*Int64
+
+  // function_ref Array.append(_:)
+  %13 = function_ref @$sSa6appendyyxnF : $@convention(method) <τ_0_0> (@in τ_0_0, @inout Array<τ_0_0>) -> ()
+  %14 = apply %13<Int64>(%11, %8) : $@convention(method) <τ_0_0> (@in τ_0_0, @inout Array<τ_0_0>) -> ()
+  dealloc_stack %11 : $*Int64
+
+  %18 = load [copy] %7 : $*StructContainingArray
+  destroy_addr %7 : $*StructContainingArray
+  dealloc_stack %7 : $*StructContainingArray
+  return %18 : $StructContainingArray
+} // CHECK: agg: 1 elt: Array<Int64>:
+  // CHECK: size: 1
+  // CHECK: agg: 1 elt: int: 105
+
 /// Test appending of a static string to an array. The construction of a static
 /// string is a bit complicated due to the use of instructions like "ptrtoint".
 /// This tests that array append works with such complex constant values as well.
@@ -1423,3 +1458,20 @@ bb0:
   // CHECK:     %1
   // CHECK:   values:
   // CHECK:     int: 991
+
+
+sil private @closure4 : $@convention(thin) () -> Int64 {
+bb0:
+  %0 = integer_literal $Builtin.Int64, 71
+  %1 = struct $Int64 (%0 : $Builtin.Int64)
+  return %1 : $Int64
+}
+
+// CHECK-LABEL: @interpretThinToThickFunction
+sil @interpretThinToThickFunction: $@convention(thin) () -> @owned @callee_guaranteed () -> Int64 {
+bb0:
+  %0 = function_ref @closure4 : $@convention(thin) () -> Int64
+  %3 = thin_to_thick_function %0 : $@convention(thin) () -> Int64 to $@callee_guaranteed () -> Int64
+  return %3 : $@callee_guaranteed () -> Int64
+} // CHECK: Returns closure: target: closure4 captures
+  // CHECK-NEXT: values: