[Bug tree-optimization/105051] consider not combining malloc + memset to calloc when inside calloc itself

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105051

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
It's more of a QOI issue, we have similar (old) bugs where we pattern-match a
memcpy loop to memcpy inside memcpy (PR56888).  The difficulty is to reliably
detect whether we're in a place where emitting a call to 'foo' will recurse. 
Unfortunately the people with knowledge in this area are too busy and given
workarounds exist this hasn't been top priority.