From beeb45def12fa063e6f7471d1ce2c0a45545f4fd Mon Sep 17 00:00:00 2001
From: Doug Gregor <dgregor@apple.com>
Date: Mon, 25 Aug 2025 16:00:21 -0700
Subject: [PATCH] [IRGen] Look for a specialized deinit when forming a call in
 IRGen

When outlining a destroy operation, we form direct calls to the deinit
of noncopyable types. For generic types, this was always calling into
unspecialized generics, which is... deeply unfortunate.

Look for a specialized deinit and call that instead. This eliminates a
compiler assertion in Embedded Swift, and should improve performance
with noncopyable generics elsewhere.

Fixes rdar://159054138 and #72627 / rdar://157131184.
---
 lib/IRGen/GenType.cpp                    |  25 +++-
 test/embedded/deinit-noncopyable-2.swift |  42 ++++++
 test/embedded/deinit-noncopyable.swift   | 164 +++++++++++++++++++++++
 3 files changed, 226 insertions(+), 5 deletions(-)
 create mode 100644 test/embedded/deinit-noncopyable-2.swift
 create mode 100644 test/embedded/deinit-noncopyable.swift

diff --git a/lib/IRGen/GenType.cpp b/lib/IRGen/GenType.cpp
index 26dc3e4b5f277..0d3b16a77111a 100644
--- a/lib/IRGen/GenType.cpp
+++ b/lib/IRGen/GenType.cpp
@@ -26,6 +26,7 @@
 #include "swift/Basic/Platform.h"
 #include "swift/Basic/SourceManager.h"
 #include "swift/IRGen/Linking.h"
+#include "swift/SIL/GenericSpecializationMangler.h"
 #include "swift/SIL/SILModule.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/ADT/SmallString.h"
@@ -2937,11 +2938,27 @@ static bool tryEmitDeinitCall(IRGenFunction &IGF,
     return true;
   }
 
+  auto deinitSILFn = deinitTable->getImplementation();
+
+  // Look for a specialization of deinit that we can call.
+  auto substitutions = ty->getContextSubstitutionMap();
+  if (!substitutions.empty() &&
+      !substitutions.getRecursiveProperties().hasArchetype()) {
+    Mangle::GenericSpecializationMangler mangler(
+        deinitSILFn->getASTContext(), deinitSILFn,
+        deinitSILFn->getSerializedKind());
+
+    auto specializedName = mangler.mangleReabstracted(
+        substitutions, /*needAlternativeMangling=*/false);
+    auto specializedFn = IGF.IGM.getSILModule().lookUpFunction(specializedName);
+    if (specializedFn)
+      deinitSILFn = specializedFn;
+  }
+
   // The deinit should take a single value parameter of the nominal type, either
   // by @owned or indirect @in convention.
-  auto deinitFn = IGF.IGM.getAddrOfSILFunction(deinitTable->getImplementation(),
-                                               NotForDefinition);
-  auto deinitTy = deinitTable->getImplementation()->getLoweredFunctionType();
+  auto deinitFn = IGF.IGM.getAddrOfSILFunction(deinitSILFn, NotForDefinition);
+  auto deinitTy = deinitSILFn->getLoweredFunctionType();
   auto deinitFP = FunctionPointer::forDirect(IGF.IGM, deinitFn,
                                              nullptr, deinitTy);
   assert(deinitTy->getNumParameters() == 1
@@ -2949,8 +2966,6 @@ static bool tryEmitDeinitCall(IRGenFunction &IGF,
          && !deinitTy->hasError()
          && "deinit should have only one parameter");
 
-  auto substitutions = ty->getContextSubstitutionMap();
-                                                     
   CalleeInfo info(deinitTy,
                   deinitTy->substGenericArgs(IGF.getSILModule(),
                                      substitutions,
diff --git a/test/embedded/deinit-noncopyable-2.swift b/test/embedded/deinit-noncopyable-2.swift
new file mode 100644
index 0000000000000..f998e505da233
--- /dev/null
+++ b/test/embedded/deinit-noncopyable-2.swift
@@ -0,0 +1,42 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend %s -g -enable-experimental-feature Embedded -c -o %t/main.o
+// REQUIRES: swift_in_compiler
+// REQUIRES: swift_feature_Embedded
+
+// https://github.com/swiftlang/swift/issues/72627 - crash with noncopyable
+// generic deinit.
+
+final class Box<T: ~Copyable> {
+  var value: T
+  init(_ value: consuming T) {
+   self.value = value
+  }
+}
+
+struct ListNode<Element: ~Copyable>: ~Copyable {
+    typealias Link = Box<ListNode<Element>>?
+
+    var element: Element
+    var next: Link
+}
+
+struct List<Element: ~Copyable>: ~Copyable {
+  typealias Link = Box<ListNode<Element>>?
+  
+  var head: Link = nil
+
+  init(head: consuming Link = nil) {
+    self.head = head
+  }
+
+  mutating func push(_ element: consuming Element) {
+    self = Self(head: Box(ListNode(element: element, next: self.head)))
+  }
+}
+
+public func main() {
+  var myList = List<Int>()
+  myList.push(1)
+  let _ = consume myList
+}
+
diff --git a/test/embedded/deinit-noncopyable.swift b/test/embedded/deinit-noncopyable.swift
new file mode 100644
index 0000000000000..2aa2b448c1989
--- /dev/null
+++ b/test/embedded/deinit-noncopyable.swift
@@ -0,0 +1,164 @@
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+// RUN: %target-swift-frontend %t/Library.swift -g -enable-experimental-feature Embedded -enable-experimental-feature Lifetimes -c -parse-as-library -o %t/Library.o -emit-module
+// RUN: %target-swift-frontend -I %t %t/Application.swift -g -enable-experimental-feature Embedded -enable-experimental-feature Lifetimes -c -o %t/main.o
+// RUN: %target-clang %target-clang-resource-dir-opt %t/main.o -o %t/a.out -dead_strip
+// RUN: %target-run %t/a.out | %FileCheck %s
+// REQUIRES: swift_in_compiler
+// REQUIRES: executable_test
+// REQUIRES: swift_feature_Embedded
+// REQUIRES: swift_feature_Lifetimes
+
+//--- Library.swift
+@safe public struct UniqueBuffer<Element: ~Copyable>: ~Copyable {
+    @usableFromInline
+    let buffer: UnsafeMutableBufferPointer<Element>
+
+    private init(_uninitializedCount count: Int) {
+      buffer = UnsafeMutableBufferPointer.allocate(capacity: count)
+    }
+
+    @inline(__always)
+    @_alwaysEmitIntoClient
+    deinit {
+        buffer.deinitialize().deallocate()
+    }
+
+    /// Allocate a new buffer with `count` elements and call the given `body` function to produce an element
+    /// for each entry.
+    public init<E>(count: Int, body: (Int) throws(E) -> Element) throws(E) {
+        self.init(_uninitializedCount: count)
+
+        for i in 0..<count {
+            do throws(E) {
+                buffer[i] = try body(i)
+            } catch {
+                // The closure threw an error. We need to deinitialize every element we've initialized up to this point.
+                for j in 0 ..< i {
+                    buffer.deinitializeElement(at: j)
+                }
+
+                throw error
+            }
+        }
+    }
+
+    /// The number of elements in the buffer.
+    public var count: Int { buffer.count }
+
+    /// Access the ith element in the buffer.
+    public subscript(_ i: Index) -> Element {
+        unsafeAddress {
+            precondition(i >= 0 && i < count)
+            return UnsafePointer(buffer.baseAddress! + i)
+        }
+
+        unsafeMutableAddress {
+            precondition(i >= 0 && i < count)
+            return buffer.baseAddress! + i
+        }
+    }
+
+    /// Index into this data structure.
+    public typealias Index = Int
+
+    /// Indices into this buffer.
+    public var indices: Range<Int> { 0..<count }
+
+    /// Produce a span covering all of the elements in the buffer.
+    public var span: Span<Element> {
+        @_lifetime(borrow self)
+        borrowing get {
+            buffer.span
+        }
+    }
+
+    /// Produce a mutable span covering all of the elements in the buffer.
+    public var mutableSpan: MutableSpan<Element> {
+        @_lifetime(&self)
+        mutating get {
+            buffer.mutableSpan
+        }
+    }
+
+    /// Run the body closure with an unsafe buffer pointer referencing the storage of this unique buffer.
+    /// 
+    /// Clients should prefer the `mutableSpan` property, which provides memory safety.
+    @unsafe public mutating func withUnsafeMutableBufferPointer<T, E>(_ body: (UnsafeMutableBufferPointer<Element>) throws(E) -> T) throws(E) -> T {
+        try body(buffer)
+    }
+}
+
+extension UniqueBuffer {
+    /// Allocate a buffer with `count` elements, all of which are a copy of `Element`.
+    public init(repeating element: Element, count: Int) {
+        self.init(_uninitializedCount: count)
+        buffer.initialize(repeating: element)
+    }
+
+    /// Allocate a buffer that contains a copy of the elements in the given collection.
+    public init(_ collection: some Collection<Element>) {
+        self.init(_uninitializedCount: collection.count)
+        _ = buffer.initialize(fromContentsOf: collection)
+    }
+}
+
+public enum BufferWrapper: ~Copyable {
+case buffer(UniqueBuffer<Int>)
+case empty
+}
+
+extension BufferWrapper {
+  public init(repeating: Int, count: Int) {
+    self = .buffer(UniqueBuffer<Int>(repeating: 17, count: 15))
+  }
+
+  public var count: Int {
+    switch self {
+    case .buffer(let unique): unique.count
+    case .empty: 0
+    }
+  }
+
+  public subscript(index: Int) -> Int {
+    switch self {
+    case .buffer(let unique): unique[index]
+    case .empty: fatalError("boom")
+    }
+  }
+}
+
+public struct BufferOfWrappers: ~Copyable {
+  let inner: UniqueBuffer<BufferWrapper>
+
+  public init() {
+    inner = UniqueBuffer(count: 17) { index in
+      .empty
+    }
+  }
+
+  public func countEm() -> Int {
+    return inner.count
+  }
+}
+
+//--- Application.swift
+import Library
+
+func test() {
+  let bufferWrapper = BufferWrapper(repeating: 17, count: 16)
+  var sum = 0
+  for i in 0..<bufferWrapper.count {
+    sum += bufferWrapper[i]
+  }
+  print(bufferWrapper.count)
+  print(sum)
+
+  let anotherBuffer = BufferOfWrappers()
+  print(anotherBuffer.countEm())
+}
+
+test()
+// CHECK: 15
+// CHECK: 17
+