Jitting expression templates yeets a UD2 instruction

[JPenuchot]

Hi,

I don't really have any way to explain that bug honestly, what happens is that I simply JIT an expression template program to dynamically generate & evaluate expression templates, and the result is an illegal instruction that is triggered by either the JIT compiler or the code it runs.

I don't have enough RAM to even compile clang in debug mode so I can't really do any further investigation, but by debugging the executable it seems like the illegal instruction was purposely called to crash the program as it's a UD2 instruction.

Here's the program if you want to replicate that bug, it only requires Blaze which is a header only library:

#include <iostream>
#include <type_traits>

#include <blaze/Blaze.h>

template<unsigned int I, typename T1, typename T2>
inline auto add( T1 const& e1, T2 const& e2 )
  -> std::enable_if_t < !(I > 0), decltype(e1)> {
  return e1;
}

template<unsigned int I, typename T1, typename T2>
inline auto add( T1 const& e1, T2 const& e2 )
  -> std::enable_if_t < (I > 0), decltype(add<I-1>( e1 + e2, e2 ))> {
  return add<I-1>( e1 + e2, e2 );
}

template<unsigned int I, typename T1, typename T2>
[[clang::jit]]
blaze::DynamicVector<float> eval ( T1 const& e1, T2 const& e2 ) {
  blaze::DynamicVector<float> res = add<I>( e1,e2 );
  return res;
}

int main ()
{
  blaze::DynamicVector<float> a( 10,1.f ), b( 10,1.f );
  for( auto const i : { 1, 2, 3, 4 } )
    std::cout << eval<i>( a, b ) << '\n';
}

The code runs perfectly when I do the same without jitting eval, so the error is clearly related to the jit compiler or generated code execution.

Regards,
Jules