[CIR][CodeGen] Implement type trait expression handling

[tommymcm]

Minimized test case:

#include <stack>
class A {
  std::stack<A> A;
} A;

Failed assertion:

clangir/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp

Line 705 in aeac352

llvm_unreachable("NYI");

Flags: -fclangir -O2

[abhijeetsharma200]

Hey, I would love to work on this issue!

I followed the installation steps from the docs of CIR to setup my project.

I tried to reproduce the issue with the provided minimal test case with the following command.

$ tmp/install-llvm/bin/clang++ -fclangir -O2 t.cpp -isysroot $(xcrun --sdk macosx --show-sdk-path)

However, the compilation fails during the frontend phase with a standard C++ error about incomplete types, before it even reaches the CIR codegen stage.

In file included from t.cpp:2:
In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/stack:128:
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/deque:251:34: error: invalid application of 'sizeof' to an incomplete type 'A'
  251 |   static const _DiffType value = sizeof(_ValueType) < 256 ? 4096 / sizeof(_ValueType) : 16;
      |                                  ^~~~~~~~~~~~~~~~~~
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/deque:265:15: note: in instantiation of template class
      'std::__deque_block_size<A, long>' requested here
  265 |               __deque_block_size<_ValueType, _DiffType>::value
      |               ^
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/deque:501:20: note: in instantiation of default argument for
      '__deque_iterator<value_type, pointer, reference, __map_pointer, difference_type>' required here
  501 |   using iterator = __deque_iterator<value_type, pointer, reference, __map_pointer, difference_type>;
      |                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/stack:156:20: note: in instantiation of template class 'std::deque<A>' requested here
  156 |   typedef typename container_type::value_type value_type;
      |                    ^
t.cpp:4:17: note: in instantiation of template class 'std::stack<A>' requested here
    4 |   std::stack<A> A;
      |                 ^
t.cpp:3:7: note: definition of 'A' is not complete until the closing '}'
    3 | class A {
      |       ^
1 error generated.

Could you suggest another test case or any mistake I made in reproducing this error? Thanks.

[tommymcm]

Let me minimize this test case some more so it doesn't depend on any system includes.

[abhijeetsharma200]

Thanks! Appreciate it!

[tommymcm]

Thanks! Appreciate it!

No problem, it's reducing now. It may take an hour or two.

[tommymcm]

Here's the minimized test:

namespace B {
template <class _0p> class B {
public:
  typedef _0p A;
  B() { __has_trivial_destructor(A); }
};
template <class _0p, class _0e0uence = B<_0p>> class A {
  _0e0uence A;
};
} // namespace B
class A {
  B::A<A> A;
} A;

[abhijeetsharma200]

Thanks! I was able to reproduce it.
I will get to making a patch for it.

[abhijeetsharma200]

Hey, I have been following these docs for the patch. But I was getting this error.

/Users/abhi/Developer/Personal/llvm-project/clang/lib/CIR/CodeGen/CIRGenExprScalar.cpp:708:49: error: no member named 'getValue' in 'clang::TypeTraitExpr'
  708 |     auto attr = CGF.getBuilder().getBoolAttr(E->getValue());

I see the getValue is part of TypeTraitExpr in the docs, but I noticed that in clang/AST/ExprCXX.h there is getBoolValue() instead. Is there a better source for docs for CIR?

[tommymcm]

This repository was recently rebased against upstream llvm. It probably changed since the 21.0.0 release that you're looking at. You can always build the doxygen locally by passing LLVM_ENABLE_DOXYGEN=On to cmake. This will make your build slower, so I recommend having a separate build for this so it's not in your dev loop.
You can also always reference the source code in the repo for less pretty documentation. You can find TypeTraitExpr in clang/include/clang/AST/ExprCXX.h

[abhijeetsharma200]

Got it thanks! I will build doxygen locally. Looking up in the source code directly can become too time-consuming, at least when getting started.

[abhijeetsharma200]

Made the PR! Please take a took when you get time.

[abhijeetsharma200]

Here's the minimized test:

namespace B {
template <class _0p> class B {
public:
  typedef _0p A;
  B() { __has_trivial_destructor(A); }
};
template <class _0p, class _0e0uence = B<_0p>> class A {
  _0e0uence A;
};
} // namespace B
class A {
  B::A<A> A;
} A;

Just for the sake of my learning, how did you minimize to this test? Any general tips/thought process? I'd like to be able to create minimal cases as well. Thanks!

[tommymcm]

Here's the minimized test:

namespace B {
template <class _0p> class B {
public:
  typedef _0p A;
  B() { __has_trivial_destructor(A); }
};
template <class _0p, class _0e0uence = B<_0p>> class A {
  _0e0uence A;
};
} // namespace B
class A {
  B::A<A> A;
} A;

Just for the sake of my learning, how did you minimize to this test? Any general tips/thought process? I'd like to be able to create minimal cases as well. Thanks!

Sorry, just saw this. I use shrinkray to minimize test cases. There are a lot of test case minimizers though, shrinkray is just easy to download and run compared to others.