Fix size and alignment for fixed

Author: Azoy

lib/IRGen/GenStruct.cpp

@@ -996,6 +996,12 @@ namespace {
       // If we have a raw layout struct who is fixed size, it means the
       // layout of the struct is fully concrete.
       if (rawLayout) {
+        // Defer to this fixed type info for type layout if the raw layout
+        // specifies size and alignment.
+        if (rawLayout->getSizeAndAlignment()) {
+          return IGM.typeLayoutCache.getOrCreateTypeInfoBasedEntry(*this, T);
+        }
+
         auto likeType = rawLayout->getResolvedLikeType(decl)->getCanonicalType();
         SILType loweredLikeType = IGM.getLoweredType(likeType);
 
@@ -1112,6 +1118,10 @@ namespace {
       // layout of the struct is dependent on the archetype of the thing it's
       // like.
       if (rawLayout) {
+        // Note: We don't have to handle the size and alignment case here for
+        // raw layout because those are always fixed, so only dependent layouts
+        // will be non-fixed.
+
         auto likeType = rawLayout->getResolvedLikeType(decl)->getCanonicalType();
         SILType loweredLikeType = IGM.getLoweredType(likeType);
 

test/IRGen/Inputs/raw_layout_multifile_b.swift

@@ -6,6 +6,13 @@ extension Foo where T == Int32 {
 
 public func foo(_: borrowing Foo<Int32>) {}
 
+@_rawLayout(size: 4, alignment: 4)
+public struct Int32Fake: ~Copyable {
+  var address: UnsafeMutablePointer<Int32> {
+    .init(Builtin.unprotectedAddressOfBorrow(self))
+  }
+}
+
 @_rawLayout(like: T)
 public struct UnsafeCell<T>: ~Copyable {
   var address: UnsafeMutablePointer<T> {

test/IRGen/raw_layout_multifile.swift

@@ -5,6 +5,17 @@
 @_rawLayout(like: Int32)
 public struct Foo<T>: ~Copyable {}
 
+// CHECK-LABEL: @"$s{{[A-Za-z0-9_]*}}5MyIntVWV" = {{.*}} %swift.vwtable
+// size
+// CHECK-SAME:  , {{i64|i32}} 4
+// stride
+// CHECK-SAME:  , {{i64|i32}} 4
+// flags: alignment 3, noncopyable
+// CHECK-SAME:  , <i32 0x800003>
+struct MyInt: ~Copyable {
+  let x: Int32Fake
+}
+
 // CHECK-LABEL: @"$s{{[A-Za-z0-9_]*}}9BadBufferVWV" = {{.*}} %swift.vwtable
 // size
 // CHECK-SAME:  , {{i64|i32}} 48
@@ -38,3 +49,9 @@ public func something2() -> Int64? {
   let buf = BadBuffer()
   return buf.buf.address[1]
 }
+
+// Force emission of MyInt's descriptor to be lazy...
+public func something3() -> Int32 {
+  let x = MyInt(x: Int32Fake())
+  return x.x.address.pointee
+}