[PATCH] D46441: [clang][CodeGenCXX] Noalias attr for copy/move constructor arguments

[Anton Bikineev via Phabricator via cfe-commits]

AntonBikineev updated this revision to Diff 146469.
AntonBikineev added a comment.
Herald added a reviewer: javed.absar.

Richard,

Thanks for the remarkable note. I've updated the patch and marked the first `llvm::Function` parameter with `noalias` attribute. Please notice, that this is not the only place where the position of the `this` pointer is assumed to always be first. As an example, another such place is here <https://clang.llvm.org/doxygen/CGCall_8cpp_source.html#l00293>. Maybe we will have to generalize it in `CGCXXABI` down the road...

> I think this standard text is in error and UB would be appropriate, but we should at least discuss whether we want to take this additional liberty not technically granted by the standard.

Should we then file an issue to the Core?
BTW, gcc already performs this opt since 8.1: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82899#c10


https://reviews.llvm.org/D46441

Files:
  lib/CodeGen/CodeGenModule.cpp
  test/CXX/except/except.spec/p14-ir.cpp
  test/CodeGenCXX/arm.cpp
  test/CodeGenCXX/arm64-constructor-return.cpp
  test/CodeGenCXX/constructor-destructor-return-this.cpp
  test/CodeGenCXX/constructor-init.cpp
  test/CodeGenCXX/constructors.cpp
  test/CodeGenCXX/copy-constructor-elim-2.cpp
  test/CodeGenCXX/copy-constructor-synthesis-2.cpp
  test/CodeGenCXX/copy-constructor-synthesis.cpp
  test/CodeGenCXX/cxx0x-delegating-ctors.cpp
  test/CodeGenCXX/default-arg-temps.cpp
  test/CodeGenCXX/default-arguments.cpp
  test/CodeGenCXX/dllexport-members.cpp
  test/CodeGenCXX/dllimport-members.cpp
  test/CodeGenCXX/dllimport.cpp
  test/CodeGenCXX/eh.cpp
  test/CodeGenCXX/float128-declarations.cpp
  test/CodeGenCXX/implicit-copy-constructor.cpp
  test/CodeGenCXX/mangle-subst-std.cpp
  test/CodeGenCXX/member-init-assignment.cpp
  test/CodeGenCXX/member-templates.cpp
  test/CodeGenCXX/microsoft-abi-eh-cleanups.cpp
  test/CodeGenCXX/microsoft-abi-extern-template.cpp
  test/CodeGenCXX/microsoft-abi-structors.cpp
  test/CodeGenCXX/microsoft-abi-virtual-inheritance.cpp
  test/CodeGenCXX/microsoft-interface.cpp
  test/CodeGenCXX/pod-member-memcpys.cpp
  test/CodeGenCXX/pointers-to-data-members.cpp
  test/CodeGenCXX/pr13396.cpp
  test/CodeGenCXX/template-anonymous-types.cpp
  test/CodeGenCXX/template-instantiation.cpp
  test/CodeGenCXX/value-init.cpp
  test/CodeGenCXX/virtual-bases.cpp
  test/CodeGenCXX/vtable-pointer-initialization.cpp
  test/CodeGenCXX/wasm-args-returns.cpp
  test/CodeGenObjCXX/implicit-copy-constructor.mm
  test/OpenMP/declare_target_codegen.cpp
  test/OpenMP/parallel_private_codegen.cpp
  test/OpenMP/teams_private_codegen.cpp
  test/OpenMP/threadprivate_codegen.cpp

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