https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112413
--- Comment #8 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jeff Law <l...@gcc.gnu.org>: https://gcc.gnu.org/g:eea25179d8d1406685b8b0995ba841605f895283 commit r14-6417-geea25179d8d1406685b8b0995ba841605f895283 Author: Mikael Pettersson <mikpeli...@gmail.com> Date: Mon Dec 11 08:40:41 2023 -0700 [PATCH] wrong code on m68k with -mlong-jump-table-offsets and -malign-int (PR target/112413) On m68k the compiler assumes that the PC-relative jump-via-jump-table instruction and the jump table are adjacent with no padding in between. When -mlong-jump-table-offsets is combined with -malign-int, a 2-byte nop may be inserted before the jump table, causing the jump to add the fetched offset to the wrong PC base and thus jump to the wrong address. Fixed by referencing the jump table via its label. On the test case in the PR the object code change is (the moveal at 16 is the nop): a: 6536 bcss 42 <f+0x42> c: e588 lsll #2,%d0 e: 203b 0808 movel %pc@(18 <f+0x18>,%d0:l),%d0 - 12: 4efb 0802 jmp %pc@(16 <f+0x16>,%d0:l) + 12: 4efb 0804 jmp %pc@(18 <f+0x18>,%d0:l) 16: 284c moveal %a4,%a4 18: 0000 0020 orib #32,%d0 1c: 0000 002c orib #44,%d0 Bootstrapped and tested on m68k-linux-gnu, no regressions. Note: I don't have commit rights to I would need assistance applying this. PR target/112413 gcc/ * config/m68k/linux.h (ASM_RETURN_CASE_JUMP): For TARGET_LONG_JUMP_TABLE_OFFSETS, reference the jump table via its label. * config/m68k/m68kelf.h (ASM_RETURN_CASE_JUMP): Likewise. * config/m68k/netbsd-elf.h (ASM_RETURN_CASE_JUMP): Likewise.
