> Output of -fstack-usage is not accurate > ======================================= > > This article mentions a "call cost": > https://mcuoneclipse.com/2015/08/21/gnu-static-stack-usage-analysis/ > > I checked for myself, by looking at the change of the stackpointer with a > debugger, and, yes, there seems to be a constant mismatch (2 bytes with > avr-gcc-5.3) between change of stack pointer and output of -fstack-usage. > In some rare cases there are more differences, which I didn't understand > yet.
That's a bug, very likely in the AVR back-end, which must be fixed by someone who knows the AVR architecture. > Wishes: > - Add stack-usage in output of -fdump-ipa-cgraph, so that you don't need to > relate information from two input files at all. I guess this is not > trivial. Or is it? It's not difficult, but there is a conflict between them because -fstack-usage is designed to be conservatively correct while -fdump-ipa-cgraph is not (it does not dump the full callgraph). -- Eric Botcazou