I see multiprecision tests being run on AIX but not on Fedora nor in BuildFarm

Hello,
I'm now porting Boost v1.69 to AIX.
While running tests of Boost.Multiprecision to AIX, I see failing tests that I do not see being run on a Fedora/Intel machine (Boost v1.69) nor in the Boost buildfarm (https://www.boost.org/development/tests/master/developer/multiprecision.html).
(They seem to deal with MPFR.)
Moreover, about all Boost 1.69 multiprecision tests, I see 259 tests on the buildfarm, 324 on my Fedora machine, but about 530 on AIX.
Why?
Thx

../boost/multiprecision/mpfr.hpp:166:134: error: no matching function for call to 'max(long unsigned int, mpfr_prec_t&)'

../bin.v2/libs/multiprecision/test/test_arithmetic_mpc.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/**test_arithmetic_mpc**.o...
../bin.v2/libs/multiprecision/test/test_arithmetic_mpfr.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/**test_arithmetic_mpfr**.o...
../bin.v2/libs/multiprecision/test/test_arithmetic_mpfr_50.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/**test_arithmetic_mpfr_50**.o...
../bin.v2/libs/multiprecision/test/test_arithmetic_mpfr_50_static.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/**test_arithmetic_mpfr_50_static**.o...
../bin.v2/libs/multiprecision/test/test_mpfr_mpc_precisions.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/**test_mpfr_mpc_precisions**.o...

../bin.v2/libs/multiprecision/test/test_complex.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/test_complex.o...
../bin.v2/libs/multiprecision/test/test_numeric_limits_mpfr.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/test_numeric_limits.o...
../bin.v2/libs/multiprecision/test/test_numeric_limits_mpfr_50.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/test_numeric_limits.o...
../bin.v2/libs/multiprecision/test/test_move_mpfr.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/test_move.o...
../bin.v2/libs/multiprecision/test/test_exp_mpfr50.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/test_exp.o...
../bin.v2/libs/multiprecision/test/test_log_mpfr50.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/test_log.o...
../bin.v2/libs/multiprecision/test/test_pow_mpfr50.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/test_pow.o...
../bin.v2/libs/multiprecision/test/test_sqrt_mpfr50.test/gcc-9.3.0/debug/address-model-64/visibility-hidden/test_sqrt.o...

Compare the Boost.Multiprecision test lists on AIX, Fedora, and the BuildFarm, starting with the linked BuildFarm results and the listed test targets. Inspect boost/multiprecision/mpfr.hpp around line 166 and the MPFR/MPC test targets to determine why they are selected differently. Done means the platform-dependent test selection and the AIX compilation error are explained and reproducible.

Written by the indexing model from the issue text.