[AutoDiff] Diagnose unsupported coroutine differentiation. (#28921)

Coroutines are functions that can yield values and suspend/resume execution.
SIL has dedicated coroutine types. Coroutines are applied via `begin_apply`.
`read` and `modify` accessors are coroutines.

Coroutine differentiation requires extra support, so it should be diagnosed
for now.

Differentiation transform:
- Generalize differentiation utilities from `ApplyInst` to `FullApplySite`.
  - `bool isArrayLiteralIntrinsic(FullApplySite)`
  - `void forEachApplyDirectResult(FullApplySite, llvm::function_ref<...>)`
    - `apply`: direct result is the `apply` result, unless the `apply` result
      has tuple-type and a single `destructure_tuple` user. Then, direct results
      are the `destructure_tuple` results.
    - `begin_apply`: direct results are the `begin_apply` results.
    - `try_apply`: direct results are successor blocks' arguments.
  - `bool LinearMapInfo::shouldDifferentiateApplySite(FullApplySite)`
- Generalize activity analysis from `ApplyInst` to `FullApplySite`.
  - Propagate variedness for `FullApplySite` through direct/indirect results and
    `inout` arguments.
  - Propagate usefulness for `FullApplySite` through arguments.
- Diagnose `begin_apply` instructions with active arguments and results in
  `PullbackEmitter::visitBeginApplyInst`.

Sema:
- Diagnose `@differentiable` attribute on `read` and `modify` coroutines.

Resolves TF-1081.

TF-1080 tracks coroutine differentiation support.
TF-1083 tracks throwing function differentiation support.

Author: dan-zheng

include/swift/AST/DiagnosticsSIL.def

@@ -541,6 +541,9 @@ NOTE(autodiff_control_flow_not_supported,none,
 // TODO(TF-645): Remove when differentiation supports `ref_element_addr`.
 NOTE(autodiff_class_property_not_supported,none,
      "differentiating class properties is not yet supported", ())
+// TODO(TF-1080): Remove when differentiation supports `begin_apply`.
+NOTE(autodiff_coroutines_not_supported,none,
+     "differentiation of coroutine calls is not yet supported", ())
 NOTE(autodiff_missing_return,none,
      "missing return for differentiation", ())
 

include/swift/SIL/ApplySite.h

@@ -503,6 +503,19 @@ class FullApplySite : public ApplySite {
     return getArguments().slice(getNumIndirectSILResults());
   }
 
+  // SWIFT_ENABLE_TENSORFLOW
+  InoutArgumentRange getInoutArguments() const {
+    switch (getKind()) {
+    case FullApplySiteKind::ApplyInst:
+      return cast<ApplyInst>(getInstruction())->getInoutArguments();
+    case FullApplySiteKind::TryApplyInst:
+      return cast<TryApplyInst>(getInstruction())->getInoutArguments();
+    case FullApplySiteKind::BeginApplyInst:
+      return cast<BeginApplyInst>(getInstruction())->getInoutArguments();
+    }
+  }
+  // SWIFT_ENABLE_TENSORFLOW END
+
   /// Returns true if \p op is the callee operand of this apply site
   /// and not an argument operand.
   bool isCalleeOperand(const Operand &op) const {

include/swift/SIL/SILInstruction.h

@@ -2041,6 +2041,27 @@ class ApplyInstBase<Impl, Base, false> : public Base {
 /// does it have the given semantics?
 bool doesApplyCalleeHaveSemantics(SILValue callee, StringRef semantics);
 
+// SWIFT_ENABLE_TENSORFLOW
+/// Predicate used to filter InoutArgumentRange.
+struct OperandToInoutArgument {
+  ArrayRef<SILParameterInfo> paramInfos;
+  OperandValueArrayRef arguments;
+  OperandToInoutArgument(ArrayRef<SILParameterInfo> paramInfos,
+                         OperandValueArrayRef arguments)
+      : paramInfos(paramInfos), arguments(arguments) {
+    assert(paramInfos.size() == arguments.size());
+  }
+  Optional<SILValue> operator()(unsigned long i) const {
+    if (paramInfos[i].isIndirectMutating())
+      return arguments[i];
+    return None;
+  }
+};
+
+using InoutArgumentRange =
+    OptionalTransformRange<IntRange<unsigned long>, OperandToInoutArgument>;
+// SWIFT_ENABLE_TENSORFLOW END
+
 /// The partial specialization of ApplyInstBase for full applications.
 /// Adds some methods relating to 'self' and to result types that don't
 /// make sense for partial applications.
@@ -2147,31 +2168,14 @@ class ApplyInstBase<Impl, Base, true>
   }
 
 // SWIFT_ENABLE_TENSORFLOW
-private:
-  /// Predicate used to filter InoutArgumentRange.
-  struct OperandToInoutArgument {
-    ArrayRef<SILParameterInfo> paramInfos;
-    OperandValueArrayRef arguments;
-    OperandToInoutArgument(const Impl &inst)
-        : paramInfos(inst.getSubstCalleeConv().getParameters()),
-          arguments(inst.getArgumentsWithoutIndirectResults()) {
-      assert(paramInfos.size() == arguments.size());
-    }
-    Optional<SILValue> operator()(unsigned long i) const {
-      if (paramInfos[i].isIndirectMutating())
-        return arguments[i];
-      return None;
-    }
-  };
-
-public:
-  using InoutArgumentRange =
-      OptionalTransformRange<IntRange<unsigned long>, OperandToInoutArgument>;
   /// Returns all `@inout` and `@inout_aliasable` arguments passed to the
   /// instruction.
   InoutArgumentRange getInoutArguments() const {
-    return InoutArgumentRange(indices(getArgumentsWithoutIndirectResults()),
-                              OperandToInoutArgument(asImpl()));
+    auto &impl = asImpl();
+    return InoutArgumentRange(
+        indices(getArgumentsWithoutIndirectResults()),
+        OperandToInoutArgument(impl.getSubstCalleeConv().getParameters(),
+                               impl.getArgumentsWithoutIndirectResults()));
   }
 // SWIFT_ENABLE_TENSORFLOW END
 };

include/swift/SILOptimizer/Utils/Differentiation/Common.h

@@ -50,9 +50,9 @@ namespace autodiff {
 /// This is being used to print short debug messages within the AD pass.
 raw_ostream &getADDebugStream();
 
-/// Returns true if this is an `ApplyInst` with `array.uninitialized_intrinsic`
-/// semantics.
-bool isArrayLiteralIntrinsic(ApplyInst *ai);
+/// Returns true if this is an full apply site whose callee has
+/// `array.uninitialized_intrinsic` semantics.
+bool isArrayLiteralIntrinsic(FullApplySite applySite);
 
 /// If the given value `v` corresponds to an `ApplyInst` with
 /// `array.uninitialized_intrinsic` semantics, returns the corresponding
@@ -76,11 +76,22 @@ ApplyInst *getAllocateUninitializedArrayIntrinsicElementAddress(SILValue v);
 /// tuple-typed and such a user exists.
 DestructureTupleInst *getSingleDestructureTupleUser(SILValue value);
 
-/// Given an `apply` instruction, apply the given callback to each of its
-/// direct results. If the `apply` instruction has a single `destructure_tuple`
-/// user, apply the callback to the results of the `destructure_tuple` user.
+/// Given a full apply site, apply the given callback to each of its
+/// "direct results".
+///
+/// - `apply`
+/// Special case because `apply` returns a single (possibly tuple-typed) result
+/// instead of multiple results. If the `apply` has a single
+/// `destructure_tuple` user, treat the `destructure_tuple` results as the
+/// `apply` direct results.
+///
+/// - `begin_apply`
+/// Apply callback to each `begin_apply` direct result.
+///
+/// - `try_apply`
+/// Apply callback to each `try_apply` successor basic block argument.
 void forEachApplyDirectResult(
-    ApplyInst *ai, llvm::function_ref<void(SILValue)> resultCallback);
+    FullApplySite applySite, llvm::function_ref<void(SILValue)> resultCallback);
 
 /// Given a function, gathers all of its formal results (both direct and
 /// indirect) in an order defined by its result type. Note that "formal results"

include/swift/SILOptimizer/Utils/Differentiation/LinearMapInfo.h

@@ -141,7 +141,7 @@ class LinearMapInfo {
                                              SILFunction *derivative);
 
 public:
-  bool shouldDifferentiateApplyInst(ApplyInst *ai);
+  bool shouldDifferentiateApplySite(FullApplySite applySite);
   bool shouldDifferentiateInstruction(SILInstruction *inst);
 
   LinearMapInfo(const LinearMapInfo &) = delete;

include/swift/SILOptimizer/Utils/Differentiation/PullbackEmitter.h

@@ -338,6 +338,8 @@ class PullbackEmitter final : public SILInstructionVisitor<PullbackEmitter> {
 
   void visitApplyInst(ApplyInst *ai);
 
+  void visitBeginApplyInst(BeginApplyInst *bai);
+
   /// Handle `struct` instruction.
   ///   Original: y = struct (x0, x1, x2, ...)
   ///    Adjoint: adj[x0] += struct_extract adj[y], #x0

lib/SILOptimizer/Analysis/DifferentiableActivityAnalysis.cpp

@@ -126,19 +126,21 @@ void DifferentiableActivityInfo::propagateVaried(
   // General rule: mark results as varied and recursively propagate variedness
   // to users of results.
   auto i = independentVariableIndex;
-  // Handle `apply`.
-  if (auto *ai = dyn_cast<ApplyInst>(inst)) {
+  // Handle full apply sites: `apply`, `try_apply`, and `begin_apply`.
+  if (FullApplySite::isa(inst)) {
+    FullApplySite applySite(inst);
     // If callee is non-varying, skip.
-    if (isWithoutDerivative(ai->getCallee()))
+    if (isWithoutDerivative(applySite.getCallee()))
       return;
     // If operand is varied, set all direct/indirect results and inout arguments
     // as varied.
     if (isVaried(operand->get(), i)) {
-      for (auto indRes : ai->getIndirectSILResults())
+      for (auto indRes : applySite.getIndirectSILResults())
         propagateVariedInwardsThroughProjections(indRes, i);
-      for (auto inoutArg : ai->getInoutArguments())
+      for (auto inoutArg : applySite.getInoutArguments())
         propagateVariedInwardsThroughProjections(inoutArg, i);
-      forEachApplyDirectResult(ai, [&](SILValue directResult) {
+      // Propagate variedness to apply site direct results.
+      forEachApplyDirectResult(applySite, [&](SILValue directResult) {
         setVariedAndPropagateToUsers(directResult, i);
       });
     }
@@ -218,7 +220,7 @@ void DifferentiableActivityInfo::propagateVariedInwardsThroughProjections(
   // Set value as varied and propagate to users.
   setVariedAndPropagateToUsers(value, independentVariableIndex);
   auto *inst = value->getDefiningInstruction();
-  if (!inst || isa<ApplyInst>(inst))
+  if (!inst || ApplySite::isa(inst))
     return;
   // Standard propagation.
   for (auto &op : inst->getAllOperands())
@@ -262,11 +264,13 @@ void DifferentiableActivityInfo::propagateUseful(
   // Propagate usefulness for the given instruction: mark operands as useful and
   // recursively propagate usefulness to defining instructions of operands.
   auto i = dependentVariableIndex;
-  // Handle indirect results in `apply`.
-  if (auto *ai = dyn_cast<ApplyInst>(inst)) {
-    if (isWithoutDerivative(ai->getCallee()))
+  // Handle full apply sites: `apply`, `try_apply`, and `begin_apply`.
+  if (FullApplySite::isa(inst)) {
+    FullApplySite applySite(inst);
+    // If callee is non-varying, skip.
+    if (isWithoutDerivative(applySite.getCallee()))
       return;
-    for (auto arg : ai->getArgumentsWithoutIndirectResults())
+    for (auto arg : applySite.getArgumentsWithoutIndirectResults())
       setUsefulAndPropagateToOperands(arg, i);
   }
   // Handle store-like instructions:

lib/SILOptimizer/Utils/Differentiation/Common.cpp

@@ -26,8 +26,9 @@ namespace autodiff {
 
 raw_ostream &getADDebugStream() { return llvm::dbgs() << "[AD] "; }
 
-bool isArrayLiteralIntrinsic(ApplyInst *ai) {
-  return ai->hasSemantics("array.uninitialized_intrinsic");
+bool isArrayLiteralIntrinsic(FullApplySite applySite) {
+  return doesApplyCalleeHaveSemantics(applySite.getCalleeOrigin(),
+                                      "array.uninitialized_intrinsic");
 }
 
 ApplyInst *getAllocateUninitializedArrayIntrinsic(SILValue v) {
@@ -71,14 +72,34 @@ DestructureTupleInst *getSingleDestructureTupleUser(SILValue value) {
 }
 
 void forEachApplyDirectResult(
-    ApplyInst *ai, llvm::function_ref<void(SILValue)> resultCallback) {
-  if (!ai->getType().is<TupleType>()) {
-    resultCallback(ai);
-    return;
+    FullApplySite applySite,
+    llvm::function_ref<void(SILValue)> resultCallback) {
+  switch (applySite.getKind()) {
+  case FullApplySiteKind::ApplyInst: {
+    auto *ai = cast<ApplyInst>(applySite.getInstruction());
+    if (!ai->getType().is<TupleType>()) {
+      resultCallback(ai);
+      return;
+    }
+    if (auto *dti = getSingleDestructureTupleUser(ai))
+      for (auto directResult : dti->getResults())
+        resultCallback(directResult);
+    break;
+  }
+  case FullApplySiteKind::BeginApplyInst: {
+    auto *bai = cast<BeginApplyInst>(applySite.getInstruction());
+    for (auto directResult : bai->getResults())
+      resultCallback(directResult);
+    break;
+  }
+  case FullApplySiteKind::TryApplyInst: {
+    auto *tai = cast<TryApplyInst>(applySite.getInstruction());
+    for (auto *succBB : tai->getSuccessorBlocks())
+      for (auto *arg : succBB->getArguments())
+        resultCallback(arg);
+    break;
+  }
   }
-  if (auto *dti = getSingleDestructureTupleUser(ai))
-    for (auto result : dti->getResults())
-      resultCallback(result);
 }
 
 void collectAllFormalResultsInTypeOrder(SILFunction &function,

lib/SILOptimizer/Utils/Differentiation/JVPEmitter.cpp

@@ -746,7 +746,7 @@ CLONE_AND_EMIT_TANGENT(DestructureTuple, dti) {
 void JVPEmitter::emitTangentForApplyInst(
     ApplyInst *ai, SILAutoDiffIndices actualIndices,
     CanSILFunctionType originalDifferentialType) {
-  assert(differentialInfo.shouldDifferentiateApplyInst(ai));
+  assert(differentialInfo.shouldDifferentiateApplySite(ai));
   auto *bb = ai->getParent();
   auto loc = ai->getLoc();
   auto &diffBuilder = getDifferentialBuilder();
@@ -1184,7 +1184,7 @@ void JVPEmitter::visitInstructionsInBlock(SILBasicBlock *bb) {
 void JVPEmitter::visitApplyInst(ApplyInst *ai) {
   // If the function should not be differentiated or its the array literal
   // initialization intrinsic, just do standard cloning.
-  if (!differentialInfo.shouldDifferentiateApplyInst(ai) ||
+  if (!differentialInfo.shouldDifferentiateApplySite(ai) ||
       isArrayLiteralIntrinsic(ai)) {
     LLVM_DEBUG(getADDebugStream() << "No active results:\n" << *ai << '\n');
     TypeSubstCloner::visitApplyInst(ai);

lib/SILOptimizer/Utils/Differentiation/LinearMapInfo.cpp

@@ -411,7 +411,7 @@ void LinearMapInfo::generateDifferentiationDataStructures(
         // Add linear map field to struct for active `apply` instructions.
         // Skip array literal intrinsic applications since array literal
         // initialization is linear and handled separately.
-        if (!shouldDifferentiateApplyInst(ai) || isArrayLiteralIntrinsic(ai))
+        if (!shouldDifferentiateApplySite(ai) || isArrayLiteralIntrinsic(ai))
           continue;
 
         LLVM_DEBUG(getADDebugStream() << "Adding linear map struct field for "
@@ -454,26 +454,29 @@ void LinearMapInfo::generateDifferentiationDataStructures(
 ///    there is a `store` of an active value into the array's buffer.
 /// 3. The instruction has both an active result (direct or indirect) and an
 ///    active argument.
-bool LinearMapInfo::shouldDifferentiateApplyInst(ApplyInst *ai) {
+bool LinearMapInfo::shouldDifferentiateApplySite(FullApplySite applySite) {
   // Function applications with an inout argument should be differentiated.
-  for (auto inoutArg : ai->getInoutArguments())
+  for (auto inoutArg : applySite.getInoutArguments())
     if (activityInfo.isActive(inoutArg, indices))
       return true;
 
   bool hasActiveDirectResults = false;
-  forEachApplyDirectResult(ai, [&](SILValue directResult) {
+  forEachApplyDirectResult(applySite, [&](SILValue directResult) {
     hasActiveDirectResults |= activityInfo.isActive(directResult, indices);
   });
-  bool hasActiveIndirectResults = llvm::any_of(ai->getIndirectSILResults(),
-      [&](SILValue result) { return activityInfo.isActive(result, indices); });
+  bool hasActiveIndirectResults =
+      llvm::any_of(applySite.getIndirectSILResults(), [&](SILValue result) {
+        return activityInfo.isActive(result, indices);
+      });
   bool hasActiveResults = hasActiveDirectResults || hasActiveIndirectResults;
 
   // TODO: Pattern match to make sure there is at least one `store` to the
   // array's active buffer.
-  if (isArrayLiteralIntrinsic(ai) && hasActiveResults)
+  // if (isArrayLiteralIntrinsic(ai) && hasActiveResults)
+  if (isArrayLiteralIntrinsic(applySite) && hasActiveResults)
     return true;
 
-  auto arguments = ai->getArgumentsWithoutIndirectResults();
+  auto arguments = applySite.getArgumentsWithoutIndirectResults();
   bool hasActiveArguments = llvm::any_of(arguments,
       [&](SILValue arg) { return activityInfo.isActive(arg, indices); });
   return hasActiveResults && hasActiveArguments;
@@ -483,19 +486,19 @@ bool LinearMapInfo::shouldDifferentiateApplyInst(ApplyInst *ai) {
 /// given the differentiation indices of the instruction's parent function.
 /// Whether the instruction should be differentiated is determined sequentially
 /// from any of the following conditions:
-/// 1. The instruction is an `apply` and `shouldDifferentiateApplyInst` returns
-///    true.
+/// 1. The instruction is a full apply site and `shouldDifferentiateApplyInst`
+///    returns true.
 /// 2. The instruction has a source operand and a destination operand, both
 ///    being active.
 /// 3. The instruction is an allocation instruction and has an active result.
 /// 4. The instruction performs reference counting, lifetime ending, access
 ///    ending, or destroying on an active operand.
 /// 5. The instruction creates an SSA copy of an active operand.
 bool LinearMapInfo::shouldDifferentiateInstruction(SILInstruction *inst) {
-  // An `apply` with an active argument and an active result (direct or
+  // A full apply site with an active argument and an active result (direct or
   // indirect) should be differentiated.
-  if (auto *ai = dyn_cast<ApplyInst>(inst))
-    return shouldDifferentiateApplyInst(ai);
+  if (FullApplySite::isa(inst))
+    return shouldDifferentiateApplySite(FullApplySite(inst));
   // Anything with an active result and an active operand should be
   // differentiated.
   auto hasActiveOperands = llvm::any_of(inst->getAllOperands(),

lib/SILOptimizer/Utils/Differentiation/PullbackEmitter.cpp

@@ -1078,7 +1078,7 @@ PullbackEmitter::getArrayAdjointElementBuffer(SILValue arrayAdjoint,
 }
 
 void PullbackEmitter::visitApplyInst(ApplyInst *ai) {
-  assert(getPullbackInfo().shouldDifferentiateApplyInst(ai));
+  assert(getPullbackInfo().shouldDifferentiateApplySite(ai));
   // Skip `array.uninitialized_intrinsic` intrinsic applications, which have
   // special `store` and `copy_addr` support.
   if (isArrayLiteralIntrinsic(ai))
@@ -1273,6 +1273,15 @@ void PullbackEmitter::visitStructInst(StructInst *si) {
   }
 }
 
+void PullbackEmitter::visitBeginApplyInst(BeginApplyInst *bai) {
+  // Diagnose `begin_apply` instructions.
+  // Coroutine differentiation is not yet supported.
+  getContext().emitNondifferentiabilityError(
+      bai, getInvoker(), diag::autodiff_coroutines_not_supported);
+  errorOccurred = true;
+  return;
+}
+
 void PullbackEmitter::visitStructExtractInst(StructExtractInst *sei) {
   assert(!sei->getField()->getAttrs().hasAttribute<NoDerivativeAttr>() &&
          "`struct_extract` with `@noDerivative` field should not be "

lib/SILOptimizer/Utils/Differentiation/VJPEmitter.cpp

@@ -430,7 +430,7 @@ void VJPEmitter::visitSwitchEnumInst(SwitchEnumInst *sei) {
 void VJPEmitter::visitApplyInst(ApplyInst *ai) {
   // If the function should not be differentiated or its the array literal
   // initialization intrinsic, just do standard cloning.
-  if (!pullbackInfo.shouldDifferentiateApplyInst(ai) ||
+  if (!pullbackInfo.shouldDifferentiateApplySite(ai) ||
       isArrayLiteralIntrinsic(ai)) {
     LLVM_DEBUG(getADDebugStream() << "No active results:\n" << *ai << '\n');
     TypeSubstCloner::visitApplyInst(ai);