Segfault on O0 and error on O1

I am trying to compile some fortran code with DVODE. I am getting a segmentation fault if I precompile the individual files with O0, and an compile-time error during `opt` if I compile it at O1. See my [Makefile](https://github.com/user-attachments/files/30259866/Makefile.txt)
[dvode.f90.txt](https://github.com/user-attachments/files/30259883/dvode.f90.txt)

When running `flang-22 -O1`, I get the following error: [error_O1.log](https://github.com/user-attachments/files/30259848/error_O1.log)
When running `flang-22 -O0` instead, I get the following segmentation fault: [error_O0.log](https://github.com/user-attachments/files/30259847/error_O0.log)

Contents of `main.f90`:
```fortran
MODULE robertston
IMPLICIT NONE

DOUBLE PRECISION, PARAMETER :: initial_time = 0.0D0
DOUBLE PRECISION, PARAMETER :: final_time = 40.D0

DOUBLE PRECISION, PARAMETER, DIMENSION(3) :: default_rate_constants = (/0.04D0, 1.0D4, 3.0D7/)
DOUBLE PRECISION, PARAMETER, DIMENSION(3) :: default_initial_abundances = (/1.D0, 0.D0, 0.D0/)

CONTAINS
PURE FUNCTION get_reaction_rates(abundances, rate_constants) RESULT(reaction_rates)
DOUBLE PRECISION, DIMENSION(3), INTENT(IN) :: abundances
DOUBLE PRECISION, DIMENSION(3), INTENT(IN) :: rate_constants

DOUBLE PRECISION, DIMENSION(SIZE(rate_constants)) :: reaction_rates

reaction_rates(1) = rate_constants(1) * abundances(1)
reaction_rates(2) = rate_constants(2) * abundances(2) * abundances(3)
reaction_rates(3) = rate_constants(3) * (abundances(2) ** 2)
END FUNCTION get_reaction_rates

PURE FUNCTION get_rates_of_change(abundances, rate_constants) RESULT(rates_of_change)
DOUBLE PRECISION, DIMENSION(3), INTENT(IN) :: abundances
DOUBLE PRECISION, DIMENSION(3), INTENT(IN) :: rate_constants

DOUBLE PRECISION, DIMENSION(SIZE(abundances)) :: rates_of_change

DOUBLE PRECISION, DIMENSION(SIZE(rate_constants)) :: reaction_rates

reaction_rates = get_reaction_rates(abundances, rate_constants)
rates_of_change(1) = -reaction_rates(1) + reaction_rates(2)
rates_of_change(2) = reaction_rates(1) - reaction_rates(2) - reaction_rates(3)
rates_of_change(3) = reaction_rates(3)
END FUNCTION get_rates_of_change

SUBROUTINE ROBERTSTON_F(NEQUATIONS, T, Y, YDOT)
INTEGER, INTENT(IN) :: NEQUATIONS

DOUBLE PRECISION, INTENT(IN) :: T
DOUBLE PRECISION, DIMENSION(NEQUATIONS), INTENT(IN) :: Y
DOUBLE PRECISION, DIMENSION(NEQUATIONS), INTENT(OUT) :: YDOT

YDOT = get_rates_of_change(Y, default_rate_constants)
END SUBROUTINE ROBERTSTON_F
END MODULE robertston

MODULE solver
USE DVODE_F90_M
USE robertston, ONLY: ROBERTSTON_F

IMPLICIT NONE

ABSTRACT INTERFACE
PURE FUNCTION I_YDOT_function(abundances, rate_constants) RESULT(YDOT)
DOUBLE PRECISION, INTENT(IN), DIMENSION(:) :: abundances
DOUBLE PRECISION, INTENT(IN), DIMENSION(:) :: rate_constants

DOUBLE PRECISION, DIMENSION(SIZE(abundances)) :: YDOT
END FUNCTION I_YDOT_function
END INTERFACE

CONTAINS
SUBROUTINE solve_abundances(nspecies, nreactions, nsteps, &
rate_constants, initial_abundances, &
final_time, YDOT_function, abundances)
INTEGER, INTENT(IN) :: nspecies, nreactions, nsteps
DOUBLE PRECISION, DIMENSION(nreactions), INTENT(IN) :: rate_constants
DOUBLE PRECISION, DIMENSION(nspecies), INTENT(IN) :: initial_abundances
DOUBLE PRECISION, INTENT(IN) :: final_time
PROCEDURE(I_YDOT_function) :: YDOT_function

DOUBLE PRECISION, DIMENSION(nspecies, nreactions), INTENT(OUT) :: abundances

DOUBLE PRECISION :: target_time
INTEGER :: time_idx
DOUBLE PRECISION :: time_step
DOUBLE PRECISION :: current_time

INTEGER :: ITASK, ISTATE
TYPE(VODE_OPTS), SAVE :: OPTIONS

CHARACTER(LEN=*), PARAMETER :: FMT = "(F15.8,E15.8,E15.8,E15.8)"

ITASK = 1
ISTATE = 1
OPTIONS = SET_OPTS(METHOD_FLAG=22, ABSERR=1.0D-8, RELERR=1.0D-8, &
USER_SUPPLIED_JACOBIAN=.False., NEVENTS=0)

current_time = 0.0D0
time_step = (final_time - current_time) / NSTEPS

abundances(:, 1) = initial_abundances
WRITE(*,FMT) current_time, abundances(1, 1), abundances(2, 1), abundances(3, 1)
DO time_idx = 1, NSTEPS
target_time = current_time + time_step

CALL DVODE_F90(F, nspecies, abundances(:, time_idx), current_time, target_time, &
& ITASK, ISTATE, OPTIONS)
current_time = target_time
WRITE(*,FMT) current_time, abundances(1, time_idx), abundances(2, time_idx), abundances(3, time_idx)
END DO

CONTAINS
SUBROUTINE F(NEQUATIONS, T, Y, YDOT)
INTEGER, INTENT(IN) :: NEQUATIONS

INTEGER, PARAMETER :: WP = KIND(1.0D0)
REAL(WP), INTENT(IN) :: T
REAL(WP), DIMENSION(NEQUATIONS), INTENT(IN) :: Y
REAL(WP), DIMENSION(NEQUATIONS), INTENT(OUT) :: YDOT

YDOT = YDOT_function(Y, rate_constants)
END SUBROUTINE F
END SUBROUTINE solve_abundances

FUNCTION get_final_abundance(nspecies, nreactions, nsteps, &
rate_constants, initial_abundances, &
final_time, YDOT_function, species_index) RESULT(final_abundance)
INTEGER, INTENT(IN) :: nspecies, nreactions, nsteps, species_index
DOUBLE PRECISION, DIMENSION(nreactions), INTENT(IN) :: rate_constants
DOUBLE PRECISION, DIMENSION(nspecies), INTENT(IN) :: initial_abundances
DOUBLE PRECISION, INTENT(IN) :: final_time
PROCEDURE(I_YDOT_function) :: YDOT_function

DOUBLE PRECISION :: final_abundance

DOUBLE PRECISION, DIMENSION(nspecies, nreactions) :: abundances

CALL solve_abundances(nspecies, nreactions, nsteps, &
rate_constants, initial_abundances, &
final_time, YDOT_function, abundances)

final_abundance = abundances(species_index, NSTEPS)
END FUNCTION get_final_abundance
END MODULE solver

PROGRAM main
USE robertston, ONLY: default_rate_constants, &
default_initial_abundances, initial_time, final_time, get_rates_of_change
USE enzyme, only: enzyme_const, enzyme_dup, enzyme_fwddiff
USE solver, only: solve_abundances, get_final_abundance

IMPLICIT NONE

INTEGER, PARAMETER :: NSPECIES = SIZE(default_initial_abundances)
INTEGER, PARAMETER :: NREACTIONS = SIZE(default_rate_constants)
INTEGER, PARAMETER :: NSTEPS = 2000
DOUBLE PRECISION, DIMENSION(NSPECIES, NSTEPS) :: abundances

DOUBLE PRECISION, DIMENSION(NREACTIONS) :: d_rate_constants = 0
DOUBLE PRECISION, DIMENSION(NREACTIONS) :: d_initial_abundances = 0
CALL enzyme_fwddiff(get_final_abundance, enzyme_const, NSPECIES, enzyme_const, NREACTIONS, &
enzyme_const, NSTEPS, &
enzyme_dup, default_rate_constants, d_rate_constants, &
enzyme_dup, default_initial_abundances, d_initial_abundances, &
enzyme_const, final_time, &
enzyme_const, get_rates_of_change, &
enzyme_const, 1)
END PROGRAM main
```

Could anyone help me out with this? Is this an issue in my Makefile, or just asking something of Enzyme it cannot do? If I remove all the calls to enzyme and just compile as usual, flang can compile it just fine.

Thank you!

Start with the attached Makefile, main.f90, error_O1.log, and error_O0.log; reproduce with flang-22 at -O0 and -O1, focusing on the enzyme_fwddiff(get_final_abundance, ...) entry point. Done means identifying whether the failure is in the build, the Enzyme/Flang interaction, or unsupported input, and documenting a reproducible diagnosis or fix.

Written by the indexing model from the issue text.