Function call during ISR - F28335

Todd Anderson78572

All:

I noticed that there is a full context save/restore when a function is called from inside of an ISR. If one were able to make that function an "Inline" function, would that allow the compiler to be smarter in terms of context save/restore (reduce the number of instructions) like it does when there is no function call?

over 13 years ago

0 Archaeologist over 13 years ago

TI__Guru* 84285 points

Yes. If the called function gets inlined, for whatever reason, there would be no need to do a full save. Is this not working in your test case?

0 Todd Anderson78572 over 13 years ago in reply to Archaeologist

Guru 14640 points

One additional caveat - we use a macro to generate the ISR code. It turns out that by inlining the called function, I saved 30 cycles of interrupt time, going from 44 cycles of execution time to 14 cycles from the ISR entry to exit. Thanks.

0 Douglas Gwyn over 13 years ago in reply to Todd Anderson78572

Expert 2210 points

Assuming we're talking about the C6xxx family, it takes 8 cycles just for the canonical interrupt vector fetch packet, and another 6 cycles for the B IRP when the interrupt handler returns. That's without doing anything at all in the interrupt handler!

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Function call during ISR - F28335