On Tue, Mar 08, 2022 at 09:49:15AM -0600, Segher Boessenkool wrote:
> > But like I said above, even if we didn't copy these XVECLEN 0 rtvecs,
> > the crash would not go away.
>
> An rtvec should never have length 0. Look at gen_rtvec for another
> example.
That is not true. In case of ASM_OPERANDS, lots of code relies that it
can use ASM_OPERANDS_{INPUT,LABEL}_LENGTH without checking if
ASM_OPERANDS_{INPUT,LABEL}_VEC is non-NULL. Those ASM*LENGTH macros are
defined as XVECLEN which I believe will just segfault if the vec is NULL:
#define XVECLEN(RTX, N) GET_NUM_ELEM (XVEC (RTX, N))
#define GET_NUM_ELEM(RTVEC) ((RTVEC)->num_elem)
#define XVEC(RTX, N) (RTL_CHECK2 (RTX, N, 'E', 'V').rt_rtvec)
cfgexpand.cc as Marek said will allocate even zero length vectors using
rtvec_alloc (0):
rtvec argvec = rtvec_alloc (ninputs);
rtvec constraintvec = rtvec_alloc (ninputs);
rtvec labelvec = rtvec_alloc (nlabels);
or e.g. in
PATTERN (insn) = gen_rtx_ASM_OPERANDS (VOIDmode, ggc_strdup (""), "", 0,
rtvec_alloc (0),
rtvec_alloc (0),
ASM_OPERANDS_LABEL_VEC (tmp),
ASM_OPERANDS_SOURCE_LOCATION(tmp));
Jakub
