Re: [PATCH 1/2] Add vect_finish_stmt_generation for sequences

On Sat, Aug 15, 2026 at 11:01 PM H.J. Lu <[email protected]> wrote:
>
> On Sun, Aug 16, 2026 at 6:36 AM H.J. Lu <[email protected]> wrote:
> >
> > On Fri, Aug 14, 2026 at 8:13 PM Richard Biener <[email protected]> wrote:
> > >
> > > The following attempts to make using gimple_build easier during
> > > vectorizer code generation by providing an overload of
> > > vect_finish_stmt_generation that handles a built sequence.
> > > In addition to inserting and finishing stmts on the sequence the
> > > ultimate result is made to be based on the passed vectorizer
> > > temporary (that gets us the fancy names).
> > >
> > > I have converted one instance in vectorizable_conversion which
> > > I'll need to handle both NOP_EXPR and VIEW_CONVERT_EXPR which
> > > gimple_build happily does correctly, but vect_gimple_build does
> > > not.
> > >
> > > Bootstrapped and tested on x86_64-unknown-linux-gnu.
> > >
> > > Does this look sensible?  I can of course sepecial-case
> > > VIEW_CONVERT_EXPR manually as well.
> > >
> > >         * tree-vect-stmts.cc (vect_finish_stmt_generation): New
> > >         overload for gimple_build sequences.
> > >         (vectorizable_conversion): Convert one instance of
> > >         vect_gimple_build to gimple_build plus
> > >         vect_finish_stmt_generation.
> > > ---
> > >  gcc/tree-vect-stmts.cc | 43 ++++++++++++++++++++++++++++++++----------
> > >  1 file changed, 33 insertions(+), 10 deletions(-)
> > >
> > > diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
> > > index a023977bc51..44090015e7a 100644
> > > --- a/gcc/tree-vect-stmts.cc
> > > +++ b/gcc/tree-vect-stmts.cc
> > > @@ -1260,7 +1260,7 @@ vect_get_vec_defs (vec_info *, slp_tree slp_node,
> > >
> > >  /* Helper function called by vect_finish_replace_stmt and
> > >     vect_finish_stmt_generation.  Set the location of the new
> > > -   statement and create and return a stmt_vec_info for it.  */
> > > +   statement.  */
> > >
> > >  static void
> > >  vect_finish_stmt_generation_1 (vec_info *,
> > > @@ -1285,8 +1285,7 @@ vect_finish_stmt_generation_1 (vec_info *,
> > >  }
> > >
> > >  /* Replace the scalar statement STMT_INFO with a new vector statement VEC_STMT,
> > > -   which sets the same scalar result as STMT_INFO did.  Create and return a
> > > -   stmt_vec_info for VEC_STMT.  */
> > > +   which sets the same scalar result as STMT_INFO did.  */
> > >
> > >  void
> > >  vect_finish_replace_stmt (vec_info *vinfo,
> > > @@ -1302,7 +1301,7 @@ vect_finish_replace_stmt (vec_info *vinfo,
> > >  }
> > >
> > >  /* Add VEC_STMT to the vectorized implementation of STMT_INFO and insert it
> > > -   before *GSI.  Create and return a stmt_vec_info for VEC_STMT.  */
> > > +   before *GSI.  */
> > >
> > >  void
> > >  vect_finish_stmt_generation (vec_info *vinfo,
> > > @@ -1344,6 +1343,31 @@ vect_finish_stmt_generation (vec_info *vinfo,
> > >    vect_finish_stmt_generation_1 (vinfo, stmt_info, vec_stmt);
> > >  }
> > >
> > > +/* Add the stmts in STMTS to the vectorized implementation of STMT_INFO and
> > > +   insert them before *GSI.  Make sure the final stmt has a result
> > > +   based on VAR.  */
> > > +
> > > +void
> > > +vect_finish_stmt_generation (vec_info *vinfo,
> > > +                            stmt_vec_info stmt_info, gimple_seq &stmts,
> > > +                            tree var, gimple_stmt_iterator *gsi)
> > > +{
> > > +  auto si = gsi_start (stmts);
> > > +  while (!gsi_end_p (si))
> > > +    {
> > > +      gimple *new_stmt = gsi_stmt (si);
> > > +      gsi_remove (&si, false);
> > > +      if (gsi_end_p (si))
> > > +       {
> > > +         tree lhs = gimple_get_lhs (new_stmt);
> > > +         gcc_assert (!SSA_NAME_VAR (lhs));
> > > +         SET_SSA_NAME_VAR_OR_IDENTIFIER (lhs, var);
> > > +       }
> > > +      vect_finish_stmt_generation (vinfo, stmt_info, new_stmt, gsi);
> > > +    }
> > > +}
> > > +
> > > +
> > >  /* We want to vectorize a call to combined function CFN with function
> > >     decl FNDECL, using VECTYPE_OUT as the type of the output and VECTYPE_IN
> > >     as the types of all inputs.  Check whether this is possible using
> > > @@ -5797,12 +5821,11 @@ vectorizable_conversion (vec_info *vinfo,
> > >             }
> > >           else
> > >             {
> > > -             new_stmt = vect_gimple_build (vec_dest, code1, vop0);
> > > -             new_temp = make_ssa_name (vec_dest, new_stmt);
> > > -             gimple_set_lhs (new_stmt, new_temp);
> > > -             vect_finish_stmt_generation (vinfo, stmt_info, new_stmt, gsi);
> > > -
> > > -             slp_node->push_vec_def (new_stmt);
> > > +             gimple_seq stmts = NULL;
> > > +             new_temp = gimple_build (&stmts, code1, vectype_out, vop0);
> > > +             vect_finish_stmt_generation (vinfo, stmt_info,
> > > +                                          stmts, vec_dest, gsi);
> > > +             slp_node->push_vec_def (new_temp);
> > >             }
> > >         }
> > >        break;
> > > --
> > > 2.51.0
> > >
> >
> > I need the patch enclosed here to avoid ICE in 2 testcases included
>
> Here is the updated patch with 3 tests.
>
> > in the patch.   But I got another ICE in bad.c:
> >
> > [hjl@gnu-zen4-1 gcc]$ ./xgcc -B./ -S -O2 -march=x86-64 ~/bugs/gcc/cvise-1/bad.c
> > during GIMPLE pass: thread
> > /export/home/hjl/bugs/gcc/cvise-1/bad.c: In function ‘collate_output___o_2’:
> > /export/home/hjl/bugs/gcc/cvise-1/bad.c:20:1: internal compiler error:
> > Segmentation fault
>
> This is
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=126876

The big comment about HJL's patch is `code1 == NOP_EXPR` should be
`CONVERT_EXPR_CODE_P (code1)` instead.

>
>
> --
> H.J.