On Fri, Jun 19, 2026 at 4:54 PM Christopher Bazley <[email protected]> wrote:
>
> On 17/06/2026 08:47, Richard Biener wrote:
> > On Tue, Jun 16, 2026 at 5:52 PM Christopher Bazley <[email protected]>
> > wrote:
> >>
> >> Hi Richard,
> >>
> >> On 09/06/2026 10:40, Richard Biener wrote:
> >>> On Wed, Jun 3, 2026 at 5:21 PM Christopher Bazley <[email protected]>
> >>> wrote:
> >>>> @@ -8075,7 +8078,12 @@ store_constructor (tree exp, rtx target, int
> >>>> cleared, poly_int64 size,
> >>>> similarly non-const type vectors. */
> >>>> icode = convert_optab_handler (vec_init_optab, mode,
> >>>> eltmode);
> >>>> }
> >>>> -
> >>>> + else
> >>>> + {
> >>>> + /* Handle variable-length vector types. */
> >>>> + icode = convert_optab_handler (vec_init_optab, mode,
> >>>> eltmode);
> >>>> + const_n_elts = constant_lower_bound (n_elts);
> >>>> + }
> >>>
> >>> And here I'd like to see
> >>>
> >>> gcc_assert (icode != CODE_FOR_nothing);
> >>
> >>
> >> Unfortunately, I cannot make this requested change because it causes the
> >> compiler to crash in an existing test case, even if I restrict the scope
> >> of the assertion to the new 'else' block.
> >
> > The 'else' block was where I wanted the assert to be, of course.
> >
> >>
> >> Reproducer:
> >>
> >> make check-gcc RUNTESTFLAGS="aarch64-sve-acle.exp=cops_bool.c"
> >>
> >> Variable values:
> >>
> >> mode = E_VNx16BImode
> >> eltmode = E_QImode
> >> icode = CODE_FOR_nothing
> >>
> >> Backtrace:
> >>
> >> #0 fancy_abort (file=file@entry=0x255f858
> >> "/work/results_sc/src-patched/gcc/expr.cc", line=line@entry=8085,
> >> function=function@entry=0x25602a0 "store_constructor")
> >> at /work/results_sc/src-patched/gcc/diagnostics/context.h:558
> >> #1 0x0000000000be9c98 in store_constructor
> >> (exp=exp@entry=0xfffff6577e58, target=target@entry=0xfffff605d408,
> >> cleared=cleared@entry=0, size=..., reverse=reverse@entry=false)
> >> at /work/results_sc/src-patched/gcc/expr.cc:8085
> >> #2 0x0000000000bec00c in expand_constructor
> >> (exp=exp@entry=0xfffff6577e58, target=0xfffff605d408,
> >> target@entry=0xfffff605d3f0, modifier=modifier@entry=EXPAND_NORMAL,
> >> avoid_temp_mem=avoid_temp_mem@entry=false)
> >> at /work/results_sc/src-patched/gcc/poly-int.h:470
> >> #3 0x0000000000bd21b8 in expand_expr_real_1 (exp=0xfffff6577e58,
> >> target=<optimized out>, tmode=E_VNx16BImode, modifier=EXPAND_NORMAL,
> >> alt_rtl=0x0, inner_reference_p=<optimized out>)
> >> at /work/results_sc/src-patched/gcc/expr.cc:11943
> >> #4 0x0000000000bd845c in expand_expr_real_gassign
> >> (g=g@entry=0xfffff65a88f0, target=target@entry=0xfffff605d3f0,
> >> tmode=tmode@entry=E_VNx16BImode, modifier=modifier@entry=EXPAND_NORMAL,
> >> alt_rtl=alt_rtl@entry=0x0,
> >> inner_reference_p=inner_reference_p@entry=false) at
> >> /work/results_sc/src-patched/gcc/gimple.h:2728
> >> #5 0x0000000000bd5604 in expand_expr_real_1
> >> (exp=exp@entry=0xfffff65bf318, target=<optimized out>,
> >> tmode=E_VNx16BImode, modifier=EXPAND_NORMAL, alt_rtl=0x0,
> >> inner_reference_p=<optimized out>)
> >> at /work/results_sc/src-patched/gcc/expr.cc:11552
> >> #6 0x0000000000bd8298 in expand_expr_real
> >> (exp=exp@entry=0xfffff65bf318, target=<optimized out>, tmode=<optimized
> >> out>, modifier=modifier@entry=EXPAND_NORMAL, alt_rtl=alt_rtl@entry=0x0,
> >> inner_reference_p=inner_reference_p@entry=false) at
> >> /work/results_sc/src-patched/gcc/expr.cc:9628
> >> #7 0x0000000000a86328 in expand_expr (exp=0xfffff65bf318,
> >> target=<optimized out>, mode=<optimized out>, modifier=EXPAND_NORMAL) at
> >> /work/results_sc/src-patched/gcc/expr.h:323
> >> #8 expand_return (retval=0xfffff74c9a28) at
> >> /work/results_sc/src-patched/gcc/cfgexpand.cc:4172
> >> #9 expand_gimple_stmt_1 (stmt=0xfffff65a89a0) at
> >> /work/results_sc/src-patched/gcc/cfgexpand.cc:4281
> >> #10 expand_gimple_stmt (stmt=stmt@entry=0xfffff65a89a0) at
> >> /work/results_sc/src-patched/gcc/cfgexpand.cc:4390
> >> #11 0x0000000000a88938 in expand_gimple_basic_block (bb=<optimized out>,
> >> asan_epilog_seq=asan_epilog_seq@entry=0x0) at
> >> /work/results_sc/src-patched/gcc/cfgexpand.cc:6507
> >> --Type <RET> for more, q to quit, c to continue without paging--
> >> #12 0x0000000000a8a568 in (anonymous namespace)::pass_expand::execute
> >> (this=<optimized out>, fun=0xfffff6591000) at
> >> /work/results_sc/src-patched/gcc/cfgexpand.cc:7254
> >> #13 0x0000000000f7ce98 in execute_one_pass (pass=pass@entry=0x3297c70)
> >> at /work/results_sc/src-patched/gcc/passes.cc:2646
> >> #14 0x0000000000f7d8d4 in execute_pass_list_1 (pass=0x3297c70) at
> >> /work/results_sc/src-patched/gcc/passes.cc:2757
> >> #15 0x0000000000f7d948 in execute_pass_list (fn=<optimized out>,
> >> pass=<optimized out>) at /work/results_sc/src-patched/gcc/passes.cc:2768
> >> #16 0x0000000000aced24 in cgraph_node::expand (this=0xfffff6588aa0) at
> >> /work/results_sc/src-patched/gcc/context.h:49
> >> #17 cgraph_node::expand (this=0xfffff6588aa0) at
> >> /work/results_sc/src-patched/gcc/cgraphunit.cc:1827
> >> #18 0x0000000000ad0dc0 in expand_all_functions () at
> >> /work/results_sc/src-patched/gcc/cgraphunit.cc:2057
> >> #19 symbol_table::compile (this=this@entry=0xfffff7406000) at
> >> /work/results_sc/src-patched/gcc/cgraphunit.cc:2435
> >> #20 0x0000000000ad3a48 in symbol_table::compile (this=0xfffff7406000) at
> >> /work/results_sc/src-patched/gcc/cgraphunit.cc:2348
> >> #21 symbol_table::finalize_compilation_unit (this=0xfffff7406000) at
> >> /work/results_sc/src-patched/gcc/cgraphunit.cc:2626
> >> #22 0x00000000010bf96c in compile_file () at
> >> /work/results_sc/src-patched/gcc/toplev.cc:482
> >> #23 0x000000000086baac in do_compile () at
> >> /work/results_sc/src-patched/gcc/toplev.cc:2228
> >> #24 toplev::main (this=this@entry=0xfffffffff078, argc=<optimized out>,
> >> argc@entry=35, argv=<optimized out>, argv@entry=0xfffffffff1f8) at
> >> /work/results_sc/src-patched/gcc/toplev.cc:2392
> >> #25 0x000000000086d094 in main (argc=35, argv=0xfffffffff1f8) at
> >> /work/results_sc/src-patched/gcc/main.cc:39
> >> (gdb) up
> >> #1 0x0000000000be9c98 in store_constructor
> >> (exp=exp@entry=0xfffff6577e58, target=target@entry=0xfffff605d408,
> >> cleared=cleared@entry=0, size=..., reverse=reverse@entry=false)
> >> at /work/results_sc/src-patched/gcc/expr.cc:8085
> >> 8085 gcc_assert (icode != CODE_FOR_nothing);
> >>
> >> Context:
> >>
> >> 8080 }
> >> 8081 else
> >> 8082 {
> >> 8083 /* Handle variable-length vector types. */
> >> 8084 icode = convert_optab_handler (vec_init_optab,
> >> mode, eltmode);
> >> 8085 gcc_assert (icode != CODE_FOR_nothing);
> >> 8086 const_n_elts = constant_lower_bound (n_elts);
> >> 8087 }
> >> 8088
> >> 8089 if (const_n_elts && icode != CODE_FOR_nothing)
> >>
> >> As far as I can tell, store_constructor is designed to handle the case
> >> where vector is null. For example, it calls the store_constructor_field
> >> function per element instead of assigning values to RTVEC_ELT (vector,
> >> eltpos).
> >
> > But right here it does
> >
> > vector = rtvec_alloc (const_n_elts);
> >
>
> That statement is in a secondary block that is only entered if
> const_n_elts && icode != CODE_FOR_nothing.
>
> In the specific failing test case, the only effect of my proposed change
> is to set const_n_elts to a non-zero value; 'vector' keeps its initial
> value because icode is still equal to CODE_FOR_nothing:
>
> rtvec vector = NULL;
>
> const_n_elts is not used outside the secondary block that is not
> entered, therefore the non-zero value of const_n_elts is irrelevant to
> the failing test case.
>
> > so not sure what you mean with 'vector is null'. Or is
> > constant_lower_bound == 0?
>
> constant_lower_bound (n_elts) is 16, as expected for mode = E_VNx16BImode.
>
> > The only case that might be relevant is a {} CTOR, one without elements.
> > But
>
> CONSTRUCTOR_NELTS (exp) is also 16, so I think that the {} case does not
> apply here.
>
> > we should have special-paths for that - are they possibly not taken for VLA
> > vector modes?
> >
> > I'll note that in general vector CTORs for BImode vectors that are not
> > constant
> > are a red herring - totally inefficent - and we should avoid those at all
> > cost.
>
> As far as I can tell, the vector is constant, and the generated code
> looks acceptable to me, e.g.
>
> ptrue p0.b, vl3
> ptrue p1.b, all
>
> from this macro body (when n == 3):
>
> svbool_t pg = svptrue_b8 (); \
> svbool_t data1 = svptrue_pat_b8 (SV_VL ## n); \
>
> > But yes, the requirement outlined is that the target needs to support
> > vec_init with E_VNx16BImode, E_QImode. If it does not the vectorizer
> > should not have created such CTOR.
>
> I don't think the vectoriser did create it, at least not in this case.
> The cops_bool.c.200t.slp2 file is full of "***** Analysis failed
> with..." messages. The test does not seem to contain any loops, either.
>
> My understanding is that the vector constructor is created by a call to
> a function such as svptrue_b8 (), e.g.
>
> svbool_t all_true = svptrue_b8 ();
>
> becomes { -1, ... } in
>
> cmp_35 = sveor_b_z ({ -1, ... }, init1_30, res_init1_34);
>
> which is the GIMPLE version of
>
> svbool_t cmp = sveor_b_z (all_true, init1, res_init1);
But {-1, ...} is a VECTOR_CST, not a CONSTRUCTOR.
> Thanks,
> --
> Christopher Bazley
> Staff Software Engineer, GNU Tools Team.
> Arm Ltd, 110 Fulbourn Road, Cambridge, CB1 9NJ, UK.
> http://www.arm.com/
