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