Loosening checks that assume only one result. Adjusting tests.

Author: BradLarson

lib/SILOptimizer/Differentiation/Common.cpp

@@ -483,10 +483,6 @@ findMinimalDerivativeConfiguration(AbstractFunctionDecl *original,
 SILDifferentiabilityWitness *getOrCreateMinimalASTDifferentiabilityWitness(
     SILModule &module, SILFunction *original, DifferentiabilityKind kind,
     IndexSubset *parameterIndices, IndexSubset *resultIndices) {
-  // AST differentiability witnesses always have a single result.
-  if (resultIndices->getCapacity() != 1 || !resultIndices->contains(0))
-    return nullptr;
-
   // Explicit differentiability witnesses only exist on SIL functions that come
   // from AST functions.
   auto *originalAFD = findAbstractFunctionDecl(original);

lib/SILOptimizer/Differentiation/Thunk.cpp

@@ -968,8 +968,8 @@ getOrCreateSubsetParametersThunkForDerivativeFunction(
         /*withoutActuallyEscaping*/ false);
   }
   assert(origFnType->getNumResults() +
-             origFnType->getNumIndirectMutatingParameters() ==
-         1);
+             origFnType->getNumIndirectMutatingParameters() >
+         0);
   if (origFnType->getNumResults() > 0 &&
       origFnType->getResults().front().isFormalDirect()) {
     auto result =

test/AutoDiff/Sema/DerivativeRegistrationCrossModule/Inputs/b.swift

@@ -25,4 +25,4 @@ func multiply_swapCustom(_ x: Float, _ y: Float) -> Float {
   var tuple = (x, y)
   swapCustom(&tuple.0, &tuple.1)
   return tuple.0 * tuple.1
-}
+}

test/AutoDiff/Sema/derivative_attr_type_checking.swift

@@ -859,13 +859,13 @@ func vjpNoSemanticResults(_ x: Float) -> (value: Void, pullback: Void) {}
 
 extension InoutParameters {
   func multipleSemanticResults(_ x: inout Float) -> Float { x }
-  @derivative(of: multipleSemanticResults)
+  @derivative(of: multipleSemanticResults, wrt: x)
   func vjpMultipleSemanticResults(_ x: inout Float) -> (
     value: Float, pullback: (Float, inout Float) -> Void
   ) { fatalError() }
 
   func inoutVoid(_ x: Float, _ void: inout Void) -> Float {}
-  @derivative(of: inoutVoid)
+  @derivative(of: inoutVoid, wrt: (x, void))
   func vjpInoutVoidParameter(_ x: Float, _ void: inout Void) -> (
     value: Float, pullback: (Float) -> Float
   ) { fatalError() }

test/AutoDiff/validation-test/forward_mode_simple.swift

@@ -1063,8 +1063,6 @@ ForwardModeTests.test("FunctionCall") {
   expectEqual(3, derivative(at: 3) { x in foo(x, 4) })
 }
 
-// FIXME(TF-1038): Support differentiable functions returning tuples.
-/*
 ForwardModeTests.test("ResultSelection") {
   func tuple(_ x: Float, _ y: Float) -> (Float, Float) {
     return (x + 1, y + 2)
@@ -1083,7 +1081,6 @@ ForwardModeTests.test("ResultSelection") {
   expectEqual(1, derivative(at: 3, 3, of: tupleGenericSecond))
   */
 }
-*/
 
 // TODO(TF-983): Support forward-mode differentiation of multiple results.
 /*