[CMake] Disable more noisy GCC warnings

[mstorsjo]

This disables the following very noisy warning:

In file included from /usr/include/c++/13/string:51,
                 from /usr/include/c++/13/bits/locale_classes.h:40,
                 from /usr/include/c++/13/bits/ios_base.h:41,
                 from /usr/include/c++/13/streambuf:43,
                 from /usr/include/c++/13/bits/streambuf_iterator.h:35,
                 from /usr/include/c++/13/iterator:66,
                 from ../include/llvm/ADT/ADL.h:13,
                 from ../include/llvm/ADT/DenseMap.h:17,
                 from ../lib/Transforms/Vectorize/VPlanAnalysis.h:12,
                 from ../lib/Transforms/Vectorize/VPlan.h:27,
                 from ../lib/Transforms/Vectorize/LoopVectorizationPlanner.h:27,                 from ../lib/Transforms/Vectorize/VPlanConstruction.cpp:14:
In static member function ‘static _Up* std::__copy_move<_IsMove, true, std::random_access_iterator_tag>::__copy_m(_Tp*, _Tp*, _Up*) [with _Tp = llvm::VPBlockBase*; _Up = llvm::VPBlockBase*; bool _IsMove = true]’,
    inlined from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:506:30,
    inlined from ‘_OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:533:42,
    inlined from ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:540:31,
    inlined from ‘_OI std::move(_II, _II, _OI) [with _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:665:38,
    inlined from ‘llvm::SmallVectorImpl<T>& llvm::SmallVectorImpl<T>::operator=(llvm::SmallVectorImpl<T>&&) [with T = llvm::VPBlockBase*]’ at ../include/llvm/ADT/SmallVector.h:1071:25,
    inlined from ‘llvm::SmallVector<T, N>& llvm::SmallVector<T, N>::operator=(llvm::SmallVector<T, N>&&) [with T = llvm::VPBlockBase*; unsigned int N = 1]’ at ../include/llvm/ADT/SmallVector.h:1259:36,
    inlined from ‘static void llvm::DomTreeBuilder::SemiNCAInfo<DomTreeT>::CalculateFromScratch(DomTreeT&, BatchUpdatePtr) [with DomTreeT = llvm::DominatorTreeBase<llvm::VPBlockBase, false>]’ at ../include/llvm/Support/GenericDomTreeConstruction.h:578:14:
/usr/include/c++/13/bits/stl_algobase.h:437:30: warning: ‘void* __builtin_memmove(void*, const void*, long unsigned int)’ forming offset 24 is out of the bounds [0, 24] of object ‘<anonymous>’ with type ‘llvm::DomTreeBuilder::SemiNCAInfo<llvm::DominatorTreeBase<llvm::VPBlockBase, false> >::RootsT’ {aka ‘llvm::SmallVector<llvm::VPBlockBase*, 1>’} [-Warray-bounds=]
  437 |             __builtin_memmove(__result, __first, sizeof(_Tp) * _Num);
      |             ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../lib/Transforms/Vectorize/VPlanDominatorTree.h:23,
                 from ../lib/Transforms/Vectorize/VPlanConstruction.cpp:17:
../include/llvm/Support/GenericDomTreeConstruction.h: In static member function ‘static void llvm::DomTreeBuilder::SemiNCAInfo<DomTreeT>::CalculateFromScratch(DomTreeT&, BatchUpdatePtr) [with DomTreeT = llvm::DominatorTreeBase<llvm::VPBlockBase, false>]’:
../include/llvm/Support/GenericDomTreeConstruction.h:578:25: note: ‘<anonymous>’ declared here
  578 |     DT.Roots = FindRoots(DT, PostViewBUI);
      |                ~~~~~~~~~^~~~~~~~~~~~~~~~~
In static member function ‘static _Up* std::__copy_move<_IsMove, true, std::random_access_iterator_tag>::__copy_m(_Tp*, _Tp*, _Up*) [with _Tp = llvm::VPBlockBase*; _Up = llvm::VPBlockBase*; bool _IsMove = true]’,
    inlined from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:506:30,
    inlined from ‘_OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:533:42,
    inlined from ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:540:31,
    inlined from ‘_OI std::move(_II, _II, _OI) [with _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:665:38,
    inlined from ‘llvm::SmallVectorImpl<T>& llvm::SmallVectorImpl<T>::operator=(llvm::SmallVectorImpl<T>&&) [with T = llvm::VPBlockBase*]’ at ../include/llvm/ADT/SmallVector.h:1094:14,
    inlined from ‘llvm::SmallVector<T, N>& llvm::SmallVector<T, N>::operator=(llvm::SmallVector<T, N>&&) [with T = llvm::VPBlockBase*; unsigned int N = 1]’ at ../include/llvm/ADT/SmallVector.h:1259:36,
    inlined from ‘static void llvm::DomTreeBuilder::SemiNCAInfo<DomTreeT>::CalculateFromScratch(DomTreeT&, BatchUpdatePtr) [with DomTreeT = llvm::DominatorTreeBase<llvm::VPBlockBase, false>]’ at ../include/llvm/Support/GenericDomTreeConstruction.h:578:14:
/usr/include/c++/13/bits/stl_algobase.h:437:30: warning: ‘void* __builtin_memmove(void*, const void*, long unsigned int)’ forming offset 24 is out of the bounds [0, 24] of object ‘<anonymous>’ with type ‘llvm::DomTreeBuilder::SemiNCAInfo<llvm::DominatorTreeBase<llvm::VPBlockBase, false> >::RootsT’ {aka ‘llvm::SmallVector<llvm::VPBlockBase*, 1>’} [-Warray-bounds=]
  437 |             __builtin_memmove(__result, __first, sizeof(_Tp) * _Num);
      |             ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/llvm/Support/GenericDomTreeConstruction.h: In static member function ‘static void llvm::DomTreeBuilder::SemiNCAInfo<DomTreeT>::CalculateFromScratch(DomTreeT&, BatchUpdatePtr) [with DomTreeT = llvm::DominatorTreeBase<llvm::VPBlockBase, false>]’:
../include/llvm/Support/GenericDomTreeConstruction.h:578:25: note: ‘<anonymous>’ declared here
  578 |     DT.Roots = FindRoots(DT, PostViewBUI);
      |                ~~~~~~~~~^~~~~~~~~~~~~~~~~

In a regular build, there's currently 14 such warning instances, but since they are so large and noisy, they are very disruptive, and they don't seem to be an actual issue in the LLVM code base.

With the -Warray-bounds warning disabled, the build instead ends up with 9 similar warnings of the kind -Wstringop-overread:

In file included from /usr/include/c++/13/string:51,
                 from /usr/include/c++/13/bits/locale_classes.h:40,
                 from /usr/include/c++/13/bits/ios_base.h:41,
                 from /usr/include/c++/13/streambuf:43,
                 from /usr/include/c++/13/bits/streambuf_iterator.h:35,
                 from /usr/include/c++/13/iterator:66,
                 from ../include/llvm/ADT/ADL.h:13,
                 from ../include/llvm/ADT/DenseMap.h:17,
                 from ../lib/Transforms/Vectorize/VPlanAnalysis.h:12,
                 from ../lib/Transforms/Vectorize/VPlan.h:27,
                 from ../lib/Transforms/Vectorize/LoopVectorizationPlanner.h:27,                 from ../lib/Transforms/Vectorize/VPlanConstruction.cpp:14:
In static member function ‘static _Up* std::__copy_move<_IsMove, true, std::random_access_iterator_tag>::__copy_m(_Tp*, _Tp*, _Up*) [with _Tp = llvm::VPBlockBase*; _Up = llvm::VPBlockBase*; bool _IsMove = true]’,
    inlined from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:506:30,
    inlined from ‘_OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:533:42,
    inlined from ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:540:31,
    inlined from ‘_OI std::move(_II, _II, _OI) [with _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:665:38,
    inlined from ‘llvm::SmallVectorImpl<T>& llvm::SmallVectorImpl<T>::operator=(llvm::SmallVectorImpl<T>&&) [with T = llvm::VPBlockBase*]’ at ../include/llvm/ADT/SmallVector.h:1071:25,
    inlined from ‘llvm::SmallVector<T, N>& llvm::SmallVector<T, N>::operator=(llvm::SmallVector<T, N>&&) [with T = llvm::VPBlockBase*; unsigned int N = 1]’ at ../include/llvm/ADT/SmallVector.h:1259:36,
    inlined from ‘static void llvm::DomTreeBuilder::SemiNCAInfo<DomTreeT>::CalculateFromScratch(DomTreeT&, BatchUpdatePtr) [with DomTreeT = llvm::DominatorTreeBase<llvm::VPBlockBase, false>]’ at ../include/llvm/Support/GenericDomTreeConstruction.h:578:14:
/usr/include/c++/13/bits/stl_algobase.h:437:30: warning: ‘void* __builtin_memmove(void*, const void*, long unsigned int)’ reading between 9 and 34359738360 bytes from a region of size 8 [-Wstringop-overread]
  437 |             __builtin_memmove(__result, __first, sizeof(_Tp) * _Num);
      |             ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../lib/Transforms/Vectorize/VPlanDominatorTree.h:23,
                 from ../lib/Transforms/Vectorize/VPlanConstruction.cpp:17:
../include/llvm/Support/GenericDomTreeConstruction.h: In static member function ‘static void llvm::DomTreeBuilder::SemiNCAInfo<DomTreeT>::CalculateFromScratch(DomTreeT&, BatchUpdatePtr) [with DomTreeT = llvm::DominatorTreeBase<llvm::VPBlockBase, false>]’:
../include/llvm/Support/GenericDomTreeConstruction.h:578:25: note: at offset 16 into source object ‘<anonymous>’ of size 24
  578 |     DT.Roots = FindRoots(DT, PostViewBUI);
      |                ~~~~~~~~~^~~~~~~~~~~~~~~~~
In static member function ‘static _Up* std::__copy_move<_IsMove, true, std::random_access_iterator_tag>::__copy_m(_Tp*, _Tp*, _Up*) [with _Tp = llvm::VPBlockBase*; _Up = llvm::VPBlockBase*; bool _IsMove = true]’,
    inlined from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:506:30,
    inlined from ‘_OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:533:42,
    inlined from ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove = true; _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:540:31,
    inlined from ‘_OI std::move(_II, _II, _OI) [with _II = llvm::VPBlockBase**; _OI = llvm::VPBlockBase**]’ at /usr/include/c++/13/bits/stl_algobase.h:665:38,
    inlined from ‘llvm::SmallVectorImpl<T>& llvm::SmallVectorImpl<T>::operator=(llvm::SmallVectorImpl<T>&&) [with T = llvm::VPBlockBase*]’ at ../include/llvm/ADT/SmallVector.h:1094:14,
    inlined from ‘llvm::SmallVector<T, N>& llvm::SmallVector<T, N>::operator=(llvm::SmallVector<T, N>&&) [with T = llvm::VPBlockBase*; unsigned int N = 1]’ at ../include/llvm/ADT/SmallVector.h:1259:36,
    inlined from ‘static void llvm::DomTreeBuilder::SemiNCAInfo<DomTreeT>::CalculateFromScratch(DomTreeT&, BatchUpdatePtr) [with DomTreeT = llvm::DominatorTreeBase<llvm::VPBlockBase, false>]’ at ../include/llvm/Support/GenericDomTreeConstruction.h:578:14:
/usr/include/c++/13/bits/stl_algobase.h:437:30: warning: ‘void* __builtin_memmove(void*, const void*, long unsigned int)’ reading between 9 and 34359738352 bytes from a region of size 8 [-Wstringop-overread]
  437 |             __builtin_memmove(__result, __first, sizeof(_Tp) * _Num);
      |             ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/llvm/Support/GenericDomTreeConstruction.h: In static member function ‘static void llvm::DomTreeBuilder::SemiNCAInfo<DomTreeT>::CalculateFromScratch(DomTreeT&, BatchUpdatePtr) [with DomTreeT = llvm::DominatorTreeBase<llvm::VPBlockBase, false>]’:
../include/llvm/Support/GenericDomTreeConstruction.h:578:25: note: at offset 16 into source object ‘<anonymous>’ of size 24
  578 |     DT.Roots = FindRoots(DT, PostViewBUI);
      |                ~~~~~~~~~^~~~~~~~~~~~~~~~~

Disable both of these, as they are extremely spammy and seem to alert on things that aren't an issue in LLVM.

[mstorsjo]

I haven't analyzed the thing that it warns about in detail, but the warnings are very very noisy and disruptive.

With this in place, building LLVM with GCC 13 "only" produces 47 warnings, but those are less spammy and seemingly accurate - and potentially actionable.

[firewave]

With this in place, building LLVM with GCC 13 "only" produces 47 warnings, but those are less spammy and seemingly accurate - and potentially actionable.

Seems reasonable to disable them for now (although I have no idea what the policy might be on this) so you have manageable output from the compiler.

[nikic]

LGTM

[nikic]

We should probably deduplicate this CMAKE_CXX_COMPILER_ID STREQUAL "GNU" check, as it's repeated 6 times in a row now...

[mstorsjo]

Sure, I can do that as a separate change.

[mstorsjo]

Argh, the github PR merge UI totally botched the huge commit message with quoted gcc diagnostics. To get a more readable version in the git history, I manually pushed a revert + a reapply with the properly formatted commit message.