[PATCH] D70671: [clang][CodeGen] Fix wrong memcpy size of no_unique_address in FieldMemcpyizer

[Senran Zhang via Phabricator via cfe-commits]

zsrkmyn created this revision.
zsrkmyn added reviewers: erichkeane, aaron.ballman, MaskRay, rjmccall.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

When generating ctor, FieldMemcpyizer wrongly treated zero-sized class members
as what should be copied, and generated wrong memcpy size under some special
circumstances. This patch tries to fix it.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D70671

Files:
  clang/lib/CodeGen/CGClass.cpp
  clang/test/CodeGenCXX/no-unique-address-2.cpp


Index: clang/test/CodeGenCXX/no-unique-address-2.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/no-unique-address-2.cpp
@@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -std=c++2a %s -emit-llvm -o - -triple x86_64-linux-gnu | FileCheck %s
+
+struct TriviallyCopyable {};
+
+struct NonTriviallyCopyable {
+  NonTriviallyCopyable() = default;
+  NonTriviallyCopyable(const NonTriviallyCopyable&) = default;
+  NonTriviallyCopyable(NonTriviallyCopyable &&) {}
+};
+
+struct Foo {
+  int i;
+  [[no_unique_address]] TriviallyCopyable m;
+  [[no_unique_address]] NonTriviallyCopyable n;
+};
+
+void call()
+{
+  Foo foo;
+  Foo foo2(static_cast<Foo&&>(foo));
+}
+
+// The memcpy call should copy exact 4 bytes for member 'int i'
+// CHECK: define {{.*}} void @_ZN3FooC2EOS_
+// CHECK:  call void @llvm.memcpy.p0i8.p0i8.i64(i8* {{.+}}, i8* {{.+}}, i64 4, i1 false)
+// CHECK:  call void @_ZN20NonTriviallyCopyableC2EOS_
Index: clang/lib/CodeGen/CGClass.cpp
===================================================================
--- clang/lib/CodeGen/CGClass.cpp
+++ clang/lib/CodeGen/CGClass.cpp
@@ -914,6 +914,8 @@
     }
 
     void addMemcpyableField(FieldDecl *F) {
+      if (F->isZeroSize(CGF.getContext()))
+        return;
       if (!FirstField)
         addInitialField(F);
       else


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