Compiler/TMS570LS0432: Division and ABI helper-functions from runtime library

There is no method by which you can force the compiler to implement a division expression a particular way.  The compiler will use either an instruction like SDIV or call a function from the RTS like __aeabi_idivmod.  

For the case where a function like __aeabi_idivmod is used, you can control what happens when divide by 0 is detected.  The TI ARM compiler, like nearly all ARM compilers, adheres to the standard ABI for the ARM architecture.  This specification requires that, when divide by 0 is detected, the function __aeabi_idiv0 (for 32-bit divide) or __aeabi_ldiv0 (for 64-bit divide) gets called.  For further details, please search this page from ARM for the term Division by zero.  

For example, you could add these two C functions to your system ...

int __aeabi_idiv0(int return_value)
{
   return 0;
}

long long __aeabi_ldiv0(long long return_value)
{
   return 0;
}

These example functions are written to always return 0, which matches the behavior of the instructions SDIV and UDIV.  

Thanks and regards,

-George

Hi George,

thank you for your answer.

Yep, it is understandable that __aeabi_idiv0 and __aeabi_ldiv0 could be redefined, thus quotient could be redefined as well. The whole helper could be reworked for 64-bit division and 32-bit modulo division, so not an issue.

But since it is not possible to force calling __aeabi_uidivmod and __aeabi_idivmod, division by zero cannot be redefined for 32 bit division. And it is a bit pity cause in accordance with the referenced by you document:

Ideally, a *divmod function should return {infinity, 0} or {0, numerator}, where infinity is an approximation.

And it is not possible to get this infinity for 32-bit division.

Nevertheless thank you for your answer. I just thought that maybe some compiler flag is available to force using helper functions for 32-bit division.

Regards,

Dmitry

P.S. If you don't mind, just another short question. Does TI provide some documentation with description of the runtime library and its functions behavior?