error: declaration is incompatible (regparm involved)

hi, i'm trying to build a project (https://github.com/riclas/rstm/) with ICC but i get the following error:

libstm/txthread.cpp(138): error: declaration is incompatible with "__attribute((regparm(3))) bool (*volatile stm::TxThread::tmbegin)(stm::TxThread *)" (declared at line 152 of "include/stm/txthread.hpp")

    __attribute__((regparm(3))) bool (*volatile TxThread::tmbegin)(TxThread*) = begin_CGL;

txthread.cpp(138): bool TM_FASTCALL (*volatile TxThread::tmbegin)(TxThread*) = begin_CGL;

txthread.hpp(152): static TM_FASTCALL bool(*volatile tmbegin)(TxThread*);

TM_FASTCALL is a macro that expands into: __attribute__((regparm(3)))

This works fine in GCC. It also works if i don't define TM_FASTCALL, but then there are other problems, and i'm not sure if this is the root cause or not.

Thanks for any tips, cheers.