[Bug target/70232] [6 regression] excessive stack usage with -O2

[arnd at linaro dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70232

--- Comment #4 from Arnd Bergmann <arnd at linaro dot org> ---
I've tried out a few more things as well, to see if the alignment of the struct
lpfc_name type or the builtin memcpy makes a different. Replacing the array of
eight bytes with a single uint64_t and scalar operations instead of string
functions makes very little difference, so it seems to be neither of them.

However, I think the wwn_to_uint64_t() function is what causes the problem.
This is supposed to be turned into a direct load or a byte reversing load
depending on endianess, but this apparently does not happen.

Adding -mbig-endian to the compiler flags brings the stack usage down, so
presumably the optimization step that identifies byteswap patters is what
causes the stack growth.