https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112508
Roger Sayle <roger at nextmovesoftware dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
CC| |roger at nextmovesoftware dot
com
Last reconfirmed| |2024-02-15
--- Comment #2 from Roger Sayle <roger at nextmovesoftware dot com> ---
The issue appears to be with (poor costing in) loop invariant store motion.
Adding the command line option "-fno-move-loop-stores" reduces the .s file from
149 lines to 54 lines, and the size of main (as reported by objdump -d) from
317 bytes to 73 bytes. To confirm that this isn't specific to this (possibly
pathological/obscure) test case, I ran the CSiBE benchmark on x86_64, comparing
"-Os" to "-Os -fno-move-loop-stores", which shows a net saving of 1606 bytes
with -fno-move-loop-stores. There are cases where -fno-move-loop-stores
reduces code size (on x86_64, and I've not investigated other targets), so I
guess it would be preferrable to use more accurate size costs instead of just
disabling this sub-pass. Note that the bigger hammer, -fno-tree-loop-im, also
avoids the code growth, but the more precise/specific -fno-move-loop-stores is
sufficient.
