What does the GCC function suffix “isra” mean?

问题:

While profiling a program compiled with gcc, I noticed functions like foo.isra.3. What does isra indicate? I notice that one of the functions is only called in a few places, and one of the arguments is always specified as a literal value. Maybe it means it's a variant of the function optimised for certain arguments?

回答1:

According to a comment on this bug report (and similar comments I could find):

ISRA is the name of the variable that gets created by IPA SRA ...

IPA SRA is an optimization option:

-fipa-sra

Perform interprocedural scalar replacement of aggregates, removal of unused parameters and replacement of parameters passed by reference by parameters passed by value.

Enabled at levels -O2, -O3 and -Os.

So most likely, it's a version of a function with those optimizations.

In the case you mentioned, it's possible that it's replacing a pass-by-reference with a pass-by-value since it knows there's no point to passing a literal by reference.