[Bug middle-end/113163] New: [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[Bug middle-end/113163] New: [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

            Bug ID: 113163
           Summary: [14 Regression][GCN] ICE in
                    vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: burnus at gcc dot gnu.org
                CC: tamar.christina at arm dot com
  Target Milestone: ---
            Target: amdgcn-amdhsa

The ICE happens when building Newlib with the GCN compiler:

during GIMPLE pass: vect
In file included from src/accel_newlib-mainline/newlib/libc/stdlib/l64a.c:24:
src/accel_newlib-mainline/newlib/libc/include/stdlib.h: In function 'l64a':
src/accel_newlib-mainline/newlib/libc/include/stdlib.h:195:9: internal compiler
error: in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420
  195 | char *  l64a (long __input);
      |         ^~~~

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

Tamar Christina <tnfchris at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tnfchris at gcc dot gnu.org

--- Comment #1 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
Hi,

This does not contain enough information for me to try to reproduce the issue.

Can you give me the full target triple, compile flag and how the compiler was
configured?

A reproducer would be helpful too.

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

--- Comment #2 from Tobias Burnus <burnus at gcc dot gnu.org> ---
Created attachment 56958
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56958&action=edit
Reduced testcase (

$ amdgcn-amdhsa-gcc -g -O2 inp5.i -march=gfx900

during GIMPLE pass: vect
inp5.i: In function '_l64a_r':
inp5.i:4:1: internal compiler error: in vect_peel_nonlinear_iv_init, at
tree-vect-loop.cc:9420
    4 | _l64a_r (struct _reent *rptr,
      | ^~~~~~~
0x94cc17 vect_peel_nonlinear_iv_init(gimple**, tree_node*, tree_node*,
tree_node*, vect_induction_op_type)
       
/net/build5-fossa-cs/scratch/tburnus/fsf.mainline.x86_64-linux-gnu-amdgcn/src/gcc-mainline/gcc/tree-vect-loop.cc:9420
0x148bb04 vect_update_ivs_after_vectorizer
        src/gcc-mainline/gcc/tree-vect-loop-manip.cc:2267
0x1498153 vect_do_peeling(_loop_vec_info*, tree_node*, tree_node*, tree_node**,
tree_node**, tree_node**, int, bool, bool, tree_node**)
        src/gcc-mainline/gcc/tree-vect-loop-manip.cc:3399
0x148714e vect_transform_loop(_loop_vec_info*, gimple*)
        src/gcc-mainline/gcc/tree-vect-loop.cc:11911
0x14c9544 vect_transform_loops
        src/gcc-mainline/gcc/tree-vectorizer.cc:1006
0x14c9bc3 try_vectorize_loop_1
        src/gcc-mainline/gcc/tree-vectorizer.cc:1152
0x14c9bc3 try_vectorize_loop
        src/gcc-mainline/gcc/tree-vectorizer.cc:1182
0x14ca224 execute
        src/gcc-mainline/gcc/tree-vectorizer.cc:1298

 * * *

Breakpoint 1, vect_peel_nonlinear_iv_init (stmts=0x7fffffffd698,
init_expr=0x7ffff7a56948, skip_niters=0x7ffff7bb8798, 
    step_expr=0x7ffff7a64ba0, induction_type=vect_step_op_shr)
    at src/gcc-mainline/gcc/tree-vect-loop.cc:9420
9420      gcc_assert (TREE_CODE (skip_niters) == INTEGER_CST);

(gdb) p debug_tree(skip_niters)
 <ssa_name 0x7ffff7bb8798
    type <integer_type 0x7ffff7b5e3f0 public unsigned SI
        size <integer_cst 0x7ffff7a64768 constant 32>
        unit-size <integer_cst 0x7ffff7a64780 constant 4>
        align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
0x7ffff7b5e3f0 precision:32 min <integer_cst 0x7ffff7b752d0 0> max <integer_cst
0x7ffff7a64b28 4294967295>>

    def_stmt GIMPLE_NOP
    version:54>
$2 = void

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

--- Comment #3 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
Thanks, taking a look.

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

--- Comment #4 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
Hmm so can't seem to reproduce it with x86_64 or aarch64.

let me build a --target=amdgcn-amdhsa

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

--- Comment #5 from Tobias Burnus <burnus at gcc dot gnu.org> ---
While higher at the call stack:

#3  0x000000000148714f in vect_transform_loop
(loop_vinfo=loop_vinfo@entry=0x350f2a0,
loop_vectorized_call=loop_vectorized_call@entry=0x0)
    at src/gcc-mainline/gcc/tree-vect-loop.cc:11911
11911     epilogue = vect_do_peeling (loop_vinfo, niters, nitersm1,
&niters_vector,

(gdb) p debug_tree(niters)
 <integer_cst 0x7ffff7bb2030 type <integer_type 0x7ffff7b5e3f0> constant 6>


One level down:

#2  0x0000000001498154 in vect_do_peeling
(loop_vinfo=loop_vinfo@entry=0x350f2a0, niters=<optimized out>,
niters@entry=0x7ffff7bb2030, 
    nitersm1=nitersm1@entry=0x7ffff7bb2c78,
niters_vector=niters_vector@entry=0x7fffffffda60,
step_vector=step_vector@entry=0x7fffffffda68, 
    niters_vector_mult_vf_var=niters_vector_mult_vf_var@entry=0x7fffffffda70,
th=<optimized out>, check_profitability=<optimized out>, 
    niters_no_overflow=<optimized out>, advance=<optimized out>)
    at src/gcc-mainline/gcc/tree-vect-loop-manip.cc:3399
3399            vect_update_ivs_after_vectorizer (loop_vinfo,
niters_vector_mult_vf,

where niters_vector_mult_vf is ssa_name that fails in the assert.


The variable seems to be generated a few lines up in the same function (line
3375 and following):

      if (!integer_onep (*step_vector))
        {
          /* On exit from the loop we will have an easy way of calcalating
             NITERS_VECTOR / STEP * STEP.  Install a dummy definition
             until then.  */
          niters_vector_mult_vf = make_ssa_name (TREE_TYPE (*niters_vector));
          SSA_NAME_DEF_STMT (niters_vector_mult_vf) = gimple_build_nop ();
          *niters_vector_mult_vf_var = niters_vector_mult_vf;
        }
      else
        vect_gen_vector_loop_niters_mult_vf (loop_vinfo, *niters_vector,
                                             &niters_vector_mult_vf);

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[burnus at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

--- Comment #6 from Tobias Burnus <burnus at gcc dot gnu.org> ---
and for that condition, we have:

3375          if (!integer_onep (*step_vector))
(gdb) p debug_tree(*step_vector)
 <integer_cst 0x7ffff7bb2f48 type <integer_type 0x7ffff7b5e3f0> constant 8>

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

Tamar Christina <tnfchris at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
           Priority|P3                          |P1
   Last reconfirmed|                            |2023-12-28
           Assignee|unassigned at gcc dot gnu.org      |tnfchris at gcc dot gnu.org

--- Comment #7 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
ok, managed to reproduce using a cross cc1.

This seems to happen because the vectorizer decides to use partial vectors to
vectorize the loop and the target picks a nonlinear induction step which we
can't support for early breaks.

The attached patch fixes it by rejecting these kind of inductions when partial
vectors are forced.

I'll submit the patch for when maintainers are back from holidays.

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

--- Comment #8 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
Created attachment 56959
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56959&action=edit
nonlinear IV

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

Tamar Christina <tnfchris at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |doko at gcc dot gnu.org

--- Comment #9 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
*** Bug 113169 has been marked as a duplicate of this bug. ***

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

--- Comment #10 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
Patch submitted

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[ams at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

Andrew Stubbs <ams at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ams at gcc dot gnu.org

--- Comment #11 from Andrew Stubbs <ams at gcc dot gnu.org> ---
(In reply to Tamar Christina from comment #7)
> This seems to happen because the vectorizer decides to use partial vectors
> to vectorize the loop and the target picks a nonlinear induction step which
> we can't support for early breaks.

In which hook is this selected?

I'm not aware of this being a deliberate choice we made...

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

--- Comment #12 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
(In reply to Andrew Stubbs from comment #11)
> (In reply to Tamar Christina from comment #7)
> > This seems to happen because the vectorizer decides to use partial vectors
> > to vectorize the loop and the target picks a nonlinear induction step which
> > we can't support for early breaks.
> 
> In which hook is this selected?
> 
> I'm not aware of this being a deliberate choice we made...

I haven't looked into why on the target we get a nonlinear induction (mostly
because I don't know much about the target). I however wasn't able to reproduce
it on SVE and x86_64 even when forcing partial vectors.

So I guess it's more accurate to say "something about the target" is making the
vectorizer pick a nonlinear induction.  most likely missing support for
something.

Note that the testcase does work if partial vectors is turned off. So It should
work fine if the vectorizer retries without partial vectors.

waiting for Richi to come back from holiday to review the patch and should be
fixed.

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.0

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

--- Comment #13 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tamar Christina <tnfchris@gcc.gnu.org>:

https://gcc.gnu.org/g:cbf569486b2decbde0308f9f4d0f0837e4cfefd9

commit r14-7036-gcbf569486b2decbde0308f9f4d0f0837e4cfefd9
Author: Tamar Christina <tamar.christina@arm.com>
Date:   Tue Jan 9 11:16:16 2024 +0000

    middle-end: rejects loops with nonlinear inductions and early breaks
[PR113163]

    We can't support nonlinear inductions other than neg when vectorizing
    early breaks and iteration count is known.

    For early break we currently require a peeled epilog but in these cases
    we can't compute the remaining values.

    gcc/ChangeLog:

            PR middle-end/113163
            * tree-vect-loop-manip.cc (vect_can_peel_nonlinear_iv_p):
            Reject non-linear inductions that aren't supported.

    gcc/testsuite/ChangeLog:

            PR middle-end/113163
            * gcc.target/gcn/pr113163.c: New test.

[Bug middle-end/113163] [14 Regression][GCN] ICE in vect_peel_nonlinear_iv_init, at tree-vect-loop.cc:9420

[tnfchris at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113163

Tamar Christina <tnfchris at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #14 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
Fixed, thanks for the report.