On 12/11/23 05:51, Mikael Pettersson wrote:
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.
2023-12-11 Mikael Pettersson <mikpeli...@gmail.com>
PR target/112413
* 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.
THanks. Installed.
jeff
