I am using

$ /Users/eschnett/gcc/bin/gfortran --version
GNU Fortran 95 (GCC) 4.1.0 20050925 (experimental)

with the options

/Users/eschnett/gcc/bin/gfortran -mlongcall -g3 -O2 -funroll-loops -Wall -Wshadow -Wsurprising -c -o $current_wd/AHFinder_exp.F.o $current_wd/AHFinder_exp.f

which leads to the error message

/Users/eschnett/Calpha/arrangements/CactusEinstein/AHFinder/src/AHFinder_exp.F: In function ‘ahfinder_exp’:
/Users/eschnett/Calpha/arrangements/CactusEinstein/AHFinder/src/AHFinder_exp.F:28: warning: unused variable ‘cctk_equals’
/Users/eschnett/Calpha/arrangements/CactusEinstein/AHFinder/src/AHFinder_exp.F:477: error: insn does not satisfy its constraints:
(insn 28938 28937 28936 8 /Users/eschnett/Calpha/arrangements/CactusEinstein/AHFinder/src/AHFinder_exp.F:221 (set (reg:DF 3 r3)
        (mem/u/c/i:DF (lo_sum:SI (reg:SI 3 r3)
                (const:SI (minus:SI (symbol_ref/u:SI ("*LC2") [flags 0x2])
                        (symbol_ref:SI ("<pic base>") [flags 0x180])))) [5 S8 A64])) 1 {movdf_low_si} (nil)
    (nil))
/Users/eschnett/Calpha/arrangements/CactusEinstein/AHFinder/src/AHFinder_exp.F:477: internal compiler error: in reload_cse_simplify_operands, at postreload.c:393
Please submit a full bug report,
with preprocessed source if appropriate.
See <URL:http://gcc.gnu.org/bugs.html> for instructions.

I attach the source code file AHFinder_exp.f and the module source AHFinder_dat.f.