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);
Thanks,
--
Christopher Bazley
Staff Software Engineer, GNU Tools Team.
Arm Ltd, 110 Fulbourn Road, Cambridge, CB1 9NJ, UK.
http://www.arm.com/
