https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71509
--- Comment #4 from Anton Blanchard <anton at samba dot org> --- Created attachment 39683 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=39683&action=edit Another bitop LHS test case Here's another issue found in the Linux kernel. Seems like this should be a single lwz/stw since the union of counter and the bitops completely overlap. The half word store followed by word load is going to prevent it from store forwarding. 0000000000000000 <set_page_slub_counters>: 0: 00 00 03 81 lwz r8,0(r3) 4: 20 00 89 78 clrldi r9,r4,32 8: c2 0f 2a 79 rldicl r10,r9,33,31 c: 00 f8 48 51 rlwimi r8,r10,31,0,0 10: 5e 00 2a 55 rlwinm r10,r9,0,1,15 14: 00 00 03 91 stw r8,0(r3) 18: 00 00 83 b0 sth r4,0(r3) 1c: 00 00 42 60 ori r2,r2,0 20: 00 00 23 81 lwz r9,0(r3) 24: 00 04 29 55 rlwinm r9,r9,0,16,0 28: 78 53 29 7d or r9,r9,r10 2c: 00 00 23 91 stw r9,0(r3) 30: 20 00 80 4e blr
