[Bug c/88160] New: Error: register save offset not a multiple of 4

[armin at diedering dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88160

            Bug ID: 88160
           Summary: Error: register save offset not a multiple of 4
           Product: gcc
           Version: 8.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: armin at diedering dot de
  Target Milestone: ---

The bug can reproduced in gcc-4.9.4 and gcc-8.1.0 for target m68k.
The error may also affect other targets. It's IMHO internal stuff.
More accurate: The bug treated by compilation for a coldfire cpu (mcpu=5475)
and 16 bit integers (-mshort) with Dwarf2 debug enabled (-g) and optimize (-O2)

test.c:
--------------------------------------------------
void *memset(void*,int,size_t);
void test(void *p) { 
  memset(p,0,166); 
  asm("":::"d4","d5","d6"); // force sve regs to sp
}
--------------------------------------------------

gcc -mcpu=5475 -g -S test.c -o-
outputs:
--------------------------------------------------
        .cfi_startproc
        lea (-12,%sp),%sp <-- allocate freame
        .cfi_def_cfa_offset 16
        movem.l #112,(%sp) <-- save regs d4-d6 
        .cfi_offset 4, -16
        .cfi_offset 5, -12
        .cfi_offset 6, -8
        .loc 1 1 81
        subq.l #2,%sp         <-- extra space - coldfire defaults 
        .cfi_def_cfa_offset 18    PREFERRED_STACK_BOUNDARY to 32
        pea 166.w
        .cfi_def_cfa_offset 22
        clr.w -(%sp)
        .cfi_def_cfa_offset 24
        move.l 24(%sp),-(%sp)
        .cfi_def_cfa_offset 28
        jsr _memset
--------------------------------------------------
thats o.k. no error

BUT with optimize (gcc 4.9.4 -O2 and above and gcc 8.1.0 -O0 and above
gcc -mcpu=5475 -g -O2 -S test.c -o-
outputs:
--------------------------------------------------
        .cfi_startproc
        .loc 1 1 79 is_stmt 0 view .LVU1
        lea (-14,%sp),%sp               <-- extra space from above now merged
        .cfi_def_cfa_offset 20          <-- BUG BUG BUG should be 18
        movem.l #112,2(%sp)             <-- 2(%sp) 2==space from above o.k.
        .cfi_offset 4, -18   <- should -16 [ -cfi_def_cfa_offset+2 ]
        .cfi_offset 5, -14   <- should -12 [ -cfi_def_cfa_offset+2+4 ]
        .cfi_offset 6, -10   <- should -8  [ -cfi_def_cfa_offset+2+8 ]
        .loc 1 1 81 is_stmt 1 view .LVU2
        pea 166.w
        .cfi_def_cfa_offset 24
        clr.w -(%sp)
        .cfi_def_cfa_offset 26
        move.l 24(%sp),-(%sp)
        .cfi_def_cfa_offset 30
        jsr _memset
--------------------------------------------------