On Fri, 19 Jul 2019, Jozef Lawrynowicz wrote: > For MSP430, the folding of identical functions marked with the "interrupt" > attribute by -fipa-icf-functions results in wrong code being generated. > Interrupts have different calling conventions than regular functions, so > inserting a CALL from one identical interrupt to another is not correct and > will result in stack corruption.
But ICF by creating an alias would be fine, correct? As I understand, the real issue here is that gcc does not know how to correctly emit a call to "interrupt" functions (because they have unusual ABI and exist basically to have their address stored somewhere). So I think the solution shouldn't be in disabling ICF altogether, but rather in adding a way to recognize that a function has quasi-unknown ABI and thus not directly callable (so any other optimization can see that it may not emit a call to this function), then teaching ICF to check that when deciding to fold by creating a wrapper. (would it be possible to tell ICF that addresses of interrupt functions are not significant so it can fold them by creating aliases?) Alexander
