[OMPIRBuilder] Hoist alloca's to entry blocks of compiler-emitted GPU reduction functions (#181359)
Fixes a bug in GPU reductions when `-O0` was used to compile GPU
reductions. There were invalid memory accesses at runtime for the
following example:
```fortran
program test_array_reduction()
integer :: red_array(1)
integer :: i
red_array = 0
!$omp target teams distribute parallel do reduction(+:red_array)
do i = 1, 100
red_array(1) = red_array(1) + 4422
end do
!$omp end target teams distribute parallel do
print *, red_array
end program test_array_reduction
```
The issue was caused by alloca's for some temp values in the combiner
region of the reduction op being inlined beyond the entry blocks of the
GPU reduction functions emitted by the compiler.
This PR fixes the issue by hoisting all alloca's to the entry block
after the reduction functions are completely emitted by the compiler.
llvm-project
c985f285 - [OMPIRBuilder] Hoist alloca's to entry blocks of compiler-emitted GPU reduction functions (#181359)
