SILGen: Lowering 'try?' and 'try!' with typed throws

lib/SILGen/JumpDest.h

@@ -29,9 +29,14 @@ namespace Lowering {
 
 struct LLVM_LIBRARY_VISIBILITY ThrownErrorInfo {
   SILValue IndirectErrorResult;
+  bool Discard;
 
-  explicit ThrownErrorInfo(SILValue IndirectErrorResult)
-    : IndirectErrorResult(IndirectErrorResult) {}
+  explicit ThrownErrorInfo(SILValue indirectErrorAddr, bool discard=false)
+    : IndirectErrorResult(indirectErrorAddr), Discard(discard) {}
+
+  static ThrownErrorInfo forDiscard() {
+    return ThrownErrorInfo(SILValue(), /*discard=*/true);
+  }
 };
 
 /// The destination of a direct jump.  Swift currently does not

lib/SILGen/SILGenExpr.cpp

@@ -1148,14 +1148,15 @@ SILGenFunction::ForceTryEmission::ForceTryEmission(SILGenFunction &SGF,
   // Set up a "catch" block for when an error occurs.
   SILBasicBlock *catchBB = SGF.createBasicBlock(FunctionSection::Postmatter);
 
-  // FIXME: typed throws
-  ASTContext &ctx = SGF.getASTContext();
-  (void) catchBB->createPhiArgument(SILType::getExceptionType(ctx),
-                                    OwnershipKind::Owned);
+  auto &errorTL = SGF.getTypeLowering(loc->getThrownError());
+  if (!errorTL.isAddressOnly()) {
+    (void) catchBB->createPhiArgument(errorTL.getLoweredType(),
+                                      OwnershipKind::Owned);
+  }
 
   SGF.ThrowDest = JumpDest(catchBB, SGF.Cleanups.getCleanupsDepth(),
                            CleanupLocation(loc),
-                           ThrownErrorInfo(/*indirectErrorAddr=*/nullptr));
+                           ThrownErrorInfo::forDiscard());
 }
 
 void SILGenFunction::ForceTryEmission::finish() {
@@ -1171,26 +1172,34 @@ void SILGenFunction::ForceTryEmission::finish() {
     // Otherwise, we need to emit it.
     SILGenSavedInsertionPoint scope(SGF, catchBB, FunctionSection::Postmatter);
 
-    // FIXME: typed throws
-    auto error = ManagedValue::forForwardedRValue(SGF, catchBB->getArgument(0));
-
     ASTContext &ctx = SGF.getASTContext();
-    if (auto diagnoseError = ctx.getDiagnoseUnexpectedError()) {
-      auto args = SGF.emitSourceLocationArgs(Loc->getExclaimLoc(), Loc);
-
-      SGF.emitApplyOfLibraryIntrinsic(
-              Loc,
-              diagnoseError,
-              SubstitutionMap(),
-              {
-                error,
-                args.filenameStartPointer,
-                args.filenameLength,
-                args.filenameIsAscii,
-                args.line
-              },
-              SGFContext());
+
+    // Consume the thrown error.
+    if (catchBB->getNumArguments() == 1) {
+      auto error = ManagedValue::forForwardedRValue(SGF, catchBB->getArgument(0));
+
+      // FIXME: for typed throws, we need a new version of this entry point that
+      // takes a generic rather than an existential.
+      if (error.getType() == SILType::getExceptionType(ctx)) {
+        if (auto diagnoseError = ctx.getDiagnoseUnexpectedError()) {
+          auto args = SGF.emitSourceLocationArgs(Loc->getExclaimLoc(), Loc);
+
+          SGF.emitApplyOfLibraryIntrinsic(
+                  Loc,
+                  diagnoseError,
+                  SubstitutionMap(),
+                  {
+                    error,
+                    args.filenameStartPointer,
+                    args.filenameLength,
+                    args.filenameIsAscii,
+                    args.line
+                  },
+                  SGFContext());
+        }
+      }
     }
+
     SGF.B.createUnreachable(Loc);
   }
 
@@ -1241,19 +1250,22 @@ RValue RValueEmitter::visitOptionalTryExpr(OptionalTryExpr *E, SGFContext C) {
   if (isByAddress)
     optAddr = optInit->getAddressForInPlaceInitialization(SGF, E);
 
-  FullExpr localCleanups(SGF.Cleanups, E);
-
   // Set up a "catch" block for when an error occurs.
   SILBasicBlock *catchBB = SGF.createBasicBlock(FunctionSection::Postmatter);
 
-  // FIXME: typed throws
-  auto *errorArg = catchBB->createPhiArgument(
-      SILType::getExceptionType(SGF.getASTContext()), OwnershipKind::Owned);
+  // FIXME: opaque values
+  auto &errorTL = SGF.getTypeLowering(E->getThrownError());
+  if (!errorTL.isAddressOnly()) {
+    (void) catchBB->createPhiArgument(errorTL.getLoweredType(),
+                                      OwnershipKind::Owned);
+  }
+
+  FullExpr localCleanups(SGF.Cleanups, E);
 
   llvm::SaveAndRestore<JumpDest> throwDest{
     SGF.ThrowDest,
     JumpDest(catchBB, SGF.Cleanups.getCleanupsDepth(), E,
-             ThrownErrorInfo(/*indirectErrorAddr=*/nullptr))};
+             ThrownErrorInfo::forDiscard())};
 
   SILValue branchArg;
   if (shouldWrapInOptional) {
@@ -1308,11 +1320,14 @@ RValue RValueEmitter::visitOptionalTryExpr(OptionalTryExpr *E, SGFContext C) {
   else
     SGF.B.createBranch(E, contBB, branchArg);
 
-  // If control branched to the failure block, inject .None into the
+  // If control branched to the failure block, inject .none into the
   // result type.
   SGF.B.emitBlock(catchBB);
   FullExpr catchCleanups(SGF.Cleanups, E);
-  (void) SGF.emitManagedRValueWithCleanup(errorArg);
+
+  // Consume the thrown error.
+  if (!errorTL.isAddressOnly())
+    (void) SGF.emitManagedRValueWithCleanup(catchBB->getArgument(0));
   catchCleanups.pop();
 
   if (isByAddress) {

lib/SILGen/SILGenStmt.cpp

@@ -1583,6 +1583,10 @@ void SILGenFunction::emitThrow(SILLocation loc, ManagedValue exnMV,
 
     // A direct error value is passed to the epilog block as a BB argument.
     args.push_back(exn);
+  } else if (ThrowDest.getThrownError().Discard) {
+    assert(!indirectErrorAddr);
+    if (exn)
+      B.createDestroyAddr(loc, exn);
   } else {
     assert(indirectErrorAddr);
 

test/SILGen/typed_throws_generic.swift

@@ -1,9 +1,10 @@
 // RUN: %target-swift-emit-silgen %s -enable-experimental-feature TypedThrows -enable-experimental-feature FullTypedThrows | %FileCheck %s
 
-public func genericThrow<E>(e: E) throws(E) -> () {
+public func genericThrow<E>(e: E) throws(E) {
   throw e
 }
 
+
 // CHECK-LABEL: sil [ossa] @$s20typed_throws_generic0C5Throw1eyx_txYKs5ErrorRzlF : $@convention(thin) <E where E : Error> (@in_guaranteed E) -> @error_indirect E {
 
 // CHECK: bb0(%0 : $*E, %1 : $*E):
@@ -14,7 +15,7 @@ public func genericThrow<E>(e: E) throws(E) -> () {
 // CHECK: throw_addr
 
 
-public func genericTryApply<E>(fn: () throws(E) -> ()) throws(E) -> () {
+public func genericTryApply<E>(fn: () throws(E) -> ()) throws(E) {
   try fn()
 }
 
@@ -38,3 +39,59 @@ public func genericTryApply<E>(fn: () throws(E) -> ()) throws(E) -> () {
 // CHECK: dealloc_stack [[ERROR]]
 // CHECK: destroy_value [[FN]]
 // CHECK: throw_addr
+
+
+public func genericOptionalTry<E>(fn: () throws(E) -> ()) -> ()? {
+  return try? fn()
+}
+
+// CHECK-LABEL: sil [ossa] @$s20typed_throws_generic0C11OptionalTry2fnytSgyyxYKXE_ts5ErrorRzlF : $@convention(thin) <E where E : Error> (@guaranteed @noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>) -> Optional<()> {
+// CHECK: bb0(%0 : @guaranteed $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>):
+// CHECK: [[FN:%.*]] = copy_value %0 : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: [[ERROR:%.*]] = alloc_stack $E
+// CHECK: [[FN_BORROW:%.*]] = begin_borrow %2 : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: try_apply [[FN_BORROW]]([[ERROR]]) : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>, normal bb1, error bb3
+
+// CHECK: bb1({{.*}} : $()):
+// CHECK: end_borrow [[FN_BORROW]] : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: dealloc_stack [[ERROR]] : $*E
+// CHECK: [[RESULT:%.*]] = tuple ()
+// CHECK: [[OPT:%.*]] = enum $Optional<()>, #Optional.some!enumelt, [[RESULT]] : $()
+// CHECK: destroy_value [[FN]] : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: br bb2([[OPT]] : $Optional<()>)
+
+// CHECK: bb2([[RESULT:%.*]] : $Optional<()>):
+// CHECK: return [[RESULT]] : $Optional<()>
+
+// CHECK: bb3:
+// CHECK: destroy_addr [[ERROR]] : $*E
+// CHECK: end_borrow [[FN_BORROW]] : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: dealloc_stack [[ERROR]] : $*E
+// CHECK: destroy_value [[FN]] : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: [[RESULT:%.*]] = enum $Optional<()>, #Optional.none!enumelt
+// CHECK: br bb2([[RESULT]] : $Optional<()>)
+
+
+public func genericForceTry<E>(fn: () throws(E) -> ()) {
+  try! fn()
+}
+
+// CHECK-LABEL: sil [ossa] @$s20typed_throws_generic0C8ForceTry2fnyyyxYKXE_ts5ErrorRzlF : $@convention(thin) <E where E : Error> (@guaranteed @noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>) -> () {
+// CHECK: bb0(%0 : @guaranteed $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>):
+// CHECK: [[FN:%.*]] = copy_value %0 : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: [[ERROR:%.*]] = alloc_stack $E
+// CHECK: [[FN_BORROW:%.*]] = begin_borrow %2 : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: try_apply [[FN_BORROW]]([[ERROR]]) : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>, normal bb1, error bb2
+
+// CHECK: bb1({{.*}} : $()):
+// CHECK: end_borrow [[FN_BORROW]] : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: dealloc_stack [[ERROR]] : $*E
+// CHECK: [[RESULT:%.*]] = tuple ()
+// CHECK: return [[RESULT]] : $()
+
+// CHECK: bb2:
+// CHECK: destroy_addr [[ERROR]] : $*E
+// CHECK: end_borrow [[FN_BORROW]] : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: dealloc_stack [[ERROR]] : $*E
+// CHECK: destroy_value [[FN]] : $@noescape @callee_guaranteed @substituted <τ_0_0> () -> @error_indirect τ_0_0 for <E>
+// CHECK: unreachable