[all-commits] [llvm/llvm-project] 3db2c5: [OpenMP][OMPIRBuilder] Collect users of a value be...

[Kareem Ergawy via All-commits]

  Branch: refs/heads/users/ergawy/handle_users_with_repeated_args
  Home:   https://github.com/llvm/llvm-project
  Commit: 3db2c56779f76838def2b8a5475d77233a004cc5
      https://github.com/llvm/llvm-project/commit/3db2c56779f76838def2b8a5475d77233a004cc5
  Author: ergawy <kareem.ergawy at amd.com>
  Date:   2025-05-08 (Thu, 08 May 2025)

  Changed paths:
    M llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
    A mlir/test/Target/LLVMIR/omp-target-call-with-repeated-parameter.mlir

  Log Message:
  -----------
  [OpenMP][OMPIRBuilder] Collect users of a value before replacing them in target outlined function

This PR fixes a crash that curently happens given the following input:
```fortran
subroutine caller()
  real :: x, y, z
  integer :: i

  !$omp target
    x = i
    call callee(x,x)
  !$omp end target
endsubroutine caller

subroutine callee(x1,x2)
  real :: x1, x2
endsubroutine callee
```

The crash happens because the following sequence of events is taken by
the `OMPIRBuilder`:
1.   ....
n.   An outlined function for the target region is created. At first the
     outlined function still refers to the SSA values from the original
     function of the target region.
n+1. The builder then iterates over the users of SSA values used in the
     target region to replace them with the corresponding function arguments
     of outlined function.
n+2. If the same instruction references the SSA value more than once (say m),
     all uses of that SSA value are replaced in the instruction.
     Deleting all m uses of the value.
n+3. The next m-1 iterations will still iterate over the same
     instruction dropping the last m-1 actual users of the value.

Hence, we call all users first before modifying them.



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