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

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
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
   20 | collate_output___o_2 (void)
      | ^~~~~~~~~~~~~~~~~~~~
0x4a21ad4 internal_error(char const*, ...)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/diagnostic-global-context.cc:787
0x2876943 crash_signal
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/toplev.cc:325
0x2aef827 path_range_query::ssa_range_in_phi(vrange&, gphi*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-path.cc:262
0x2aefb42 path_range_query::range_defined_in_block(vrange&,
tree_node*, basic_block_def*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-path.cc:303
0x2aef2d4 path_range_query::internal_range_of_expr(vrange&, tree_node*, gimple*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-path.cc:160
0x2aef42f path_range_query::range_of_expr(vrange&, tree_node*, gimple*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-path.cc:180
0x23482e9 fur_stmt::get_operand(vrange&, tree_node*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-fold.cc:145
0x234a8c1 fold_using_range::range_of_range_op(vrange&,
gimple_range_op_handler&, fur_source&)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-fold.cc:817
0x2349ec1 fold_using_range::fold_stmt(vrange&, gimple*, fur_source&, tree_node*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-fold.cc:706
0x23488b6 fold_range(vrange&, gimple*, range_query*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-fold.cc:321
0x2af1279 path_range_query::range_of_stmt(vrange&, gimple*, tree_node*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-path.cc:685
0x2aefb90 path_range_query::range_defined_in_block(vrange&,
tree_node*, basic_block_def*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-path.cc:309
0x2aef2d4 path_range_query::internal_range_of_expr(vrange&, tree_node*, gimple*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-path.cc:160
0x2aef42f path_range_query::range_of_expr(vrange&, tree_node*, gimple*)
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-range-path.cc:180
0x4823aa7 gimple_match_range_of_expr
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-match-head.cc:532
0x487bb10 gimple_simplify_PLUS_EXPR(gimple_match_op*, gimple**,
tree_node* (*)(tree_node*), code_helper, tree_node*, tree_node*,
tree_node*)
/export/build/gnu/tools-build/gcc-gitlab-test-debug/build-x86_64-linux/gcc/gimple-match-1.cc:19695
0x359c364 gimple_simplify(gimple_match_op*, gimple**, tree_node*
(*)(tree_node*), code_helper, tree_node*, tree_node*, tree_node*)
/export/build/gnu/tools-build/gcc-gitlab-test-debug/build-x86_64-linux/gcc/gimple-match-7.cc:25870
0x37005ab gimple_resimplify2
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-match-exports.cc:1029
0x36fdcf4 gimple_match_op::resimplify(gimple**, tree_node* (*)(tree_node*))
/export/gnu/import/git/gitlab/x86-gcc-test/gcc/gimple-match-exports.cc:113
0x31cf93f gimple_simplify_POINTER_PLUS_EXPR(gimple_match_op*,
gimple**, tree_node* (*)(tree_node*), code_helper, tree_node*,
tree_node*, tree_node*)
/export/build/gnu/tools-build/gcc-gitlab-test-debug/build-x86_64-linux/gcc/gimple-match-3.cc:12679
./cc1 -quiet -iprefix
/export/build/gnu/tools-build/gcc-gitlab-test-debug/build-x86_64-linux/gcc/../lib/gcc/x86_64-pc-linux-gnu/17.0.0/
-isystem ./include -isystem ./include-fixed
/export/home/hjl/bugs/gcc/cvise-1/bad.c -quiet -dumpbase bad.c
-dumpbase-ext .c -march=x86-64 -mtls-dialect=gnu2 -O2 -o bad.s
Please submit a full bug report, with preprocessed source (by using
-freport-bug).
Please include the complete backtrace with any bug report.
See <https://gcc.gnu.org/bugs/> for instructions.
[hjl@gnu-zen4-1 gcc]$


-- 
H.J.

From 879f54bb30e2c1859f59e4132ece8375520c54ab Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <[email protected]>
Date: Sat, 15 Aug 2026 08:35:23 +0800
Subject: [PATCH] Fix Add vect_finish_stmt_generation for sequences

Signed-off-by: H.J. Lu <[email protected]>
---
 gcc/testsuite/g++.target/i386/pr126788-2.C | 169 +++++++++++++++++++++
 gcc/testsuite/g++.target/i386/pr126788-3.C |  30 ++++
 gcc/tree-vect-stmts.cc                     |  23 ++-
 3 files changed, 217 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/g++.target/i386/pr126788-2.C
 create mode 100644 gcc/testsuite/g++.target/i386/pr126788-3.C

diff --git a/gcc/testsuite/g++.target/i386/pr126788-2.C b/gcc/testsuite/g++.target/i386/pr126788-2.C
new file mode 100644
index 00000000000..2cd2ca2d76a
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/pr126788-2.C
@@ -0,0 +1,169 @@
+/* { dg-do compile } */
+/* { dg-options "-fno-checking -O2 -march=x86-64-v4 -std=c++20" } */
+
+char __parse_integer___buf[32];
+template <typename _Tp> using remove_reference_t = _Tp;
+template <typename _Tp, typename _Up>
+constexpr bool is_same_v = __is_same (_Tp, _Up);
+template <typename _Tp, typename _Up>
+concept __same_as = is_same_v<_Tp, _Up>;
+template <typename _Tp, typename _Up>
+concept same_as = __same_as<_Up, _Tp>;
+struct __is_integer
+{
+  enum
+  {
+    __value = 1
+  };
+};
+using wstring_view = int;
+template <typename, typename> class basic_format_context;
+template <typename> struct basic_format_parse_context
+{
+  int *begin ();
+  int *end ();
+};
+template <typename, typename> struct formatter;
+namespace __format
+{
+template <typename _CharT>
+concept __char = same_as<_CharT, wchar_t>;
+template <typename> struct _Sink_iter
+{
+};
+template <typename _CharT>
+using __format_context = basic_format_context<_CharT, _CharT>;
+} // namespace __format
+using wformat_context = __format::__format_context<wchar_t>;
+namespace __format
+{
+template <typename _CharT>
+void
+__parse_integer (_CharT *__first, _CharT *)
+{
+  for (int __i = 0; __i < 32 && __first + __i; ++__i)
+    __parse_integer___buf[__i] = __i;
+  __parse_integer (__parse_integer___buf, __parse_integer___buf);
+}
+enum _Pres_type
+{
+};
+template <typename _CharT> struct _Spec
+{
+  void
+  _M_parse_width (int *__first, int *__last,
+                  basic_format_parse_context<_CharT>)
+  {
+    __parse_integer (__first, __last);
+  }
+};
+template <__char _CharT> struct __formatter_int
+{
+  _Pres_type _AsInteger;
+  _CharT
+  _M_do_parse (basic_format_parse_context<_CharT> __pc, _Pres_type)
+  {
+    _Spec<_CharT> __spec;
+    auto __last = __pc.end (), __first = __pc.begin ();
+    __spec._M_parse_width (__first, __last, __pc);
+    return 0;
+  }
+  template <typename>
+  _CharT
+  _M_parse (basic_format_parse_context<_CharT> __pc)
+  {
+    _M_do_parse (__pc, _AsInteger);
+    return 0;
+  }
+};
+template <typename>
+constexpr bool __is_formattable_integer = __is_integer::__value;
+template <typename _Tp>
+concept __formattable_integer = __is_formattable_integer<_Tp>;
+} // namespace __format
+template <__format::__formattable_integer _Tp, __format::__char _CharT>
+struct formatter<_Tp, _CharT>
+{
+  _CharT
+  parse (basic_format_parse_context<_CharT> __pc)
+  {
+    _M_f.template _M_parse<_Tp> (__pc);
+    return 0;
+  }
+  __format::__formatter_int<_CharT> _M_f;
+};
+namespace __format
+{
+enum _Arg_t
+{
+  _Arg_u128
+};
+}
+int _M_val;
+__format::_Arg_t _M_type;
+struct
+{
+  template <typename _Visitor>
+  void
+  _M_visit (_Visitor)
+  {
+    switch (_M_type)
+      {
+        using enum __format::_Arg_t;
+      case _Arg_u128:
+        _Visitor () (_M_val);
+      }
+  }
+} __visit_format_arg___arg;
+template <typename _Visitor>
+void
+__visit_format_arg (_Visitor)
+{
+  __visit_format_arg___arg._M_visit (_Visitor ());
+}
+template <typename, typename> struct basic_format_context
+{
+  template <typename _Tp> using formatter_type = formatter<_Tp, wchar_t>;
+};
+namespace __format
+{
+struct : basic_format_parse_context<wchar_t>
+{
+} _M_pc;
+void _M_scan ();
+struct _Scanner
+{
+  _Scanner (int);
+  virtual void _M_format_arg (unsigned long);
+};
+template <typename _Out, typename _CharT> struct _Formatting_scanner : _Scanner
+{
+  _Formatting_scanner (basic_format_context<_Out, _CharT>, int __str)
+      : _Scanner (__str)
+  {
+  }
+  void
+  _M_format_arg (unsigned long)
+  {
+    __visit_format_arg (
+        [] (auto __arg)
+          {
+            typename basic_format_context<_Out, _CharT>::formatter_type<
+                remove_reference_t<decltype (__arg)>>
+                __f;
+            __f.parse (_M_pc);
+          });
+  }
+};
+template <unsigned = 0>
+_Sink_iter<wchar_t>
+__do_vformat_to (_Sink_iter<wchar_t> x, int __fmt,
+                 __format_context<wchar_t> &__ctx)
+{
+  _Formatting_scanner __scanner (__ctx, __fmt);
+  _M_scan ();
+  return x;
+}
+template _Sink_iter<wchar_t> __do_vformat_to (_Sink_iter<wchar_t>,
+                                              wstring_view, wformat_context &);
+}
diff --git a/gcc/testsuite/g++.target/i386/pr126788-3.C b/gcc/testsuite/g++.target/i386/pr126788-3.C
new file mode 100644
index 00000000000..17723cdcba5
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/pr126788-3.C
@@ -0,0 +1,30 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -march=x86-64-v4 -std=c++17" } */
+
+extern int _M_current;
+extern int end ();
+struct color
+{
+  char r;
+  struct
+  {
+    unsigned char g;
+    unsigned char b;
+  } m_24bit;
+  color (char g, char b)
+  {
+    m_24bit.g = g;
+    m_24bit.b = b;
+  }
+};
+void
+set_style_bg_color (color)
+{
+  for (;;)
+    {
+      const unsigned char g = _M_current;
+      if (end ())
+	break;
+      set_style_bg_color (color (g, _M_current));
+    }
+}
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index 070981dbdb3..5330da1edd8 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -5828,11 +5828,24 @@ vectorizable_conversion (vec_info *vinfo,
 	    }
 	  else
 	    {
-	      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);
+	      if (code1 == NOP_EXPR)
+		{
+		  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);
+		}
+	      else
+		{
+		  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;
-- 
2.55.0

struct obstack
{
  char *next_free;
} collate_output_extrapool;

extern struct obstack _obstack_newchunk (void);
extern char obstack_int32_grow___o_2;
extern char obstack_int32_grow___o1_1;
extern long nwcs;
extern int collate_output_runp_6;
void
obstack_int32_grow (struct obstack *obstack, int data)
{
  struct obstack __o = *obstack;
  if (__o.next_free + 4 > &obstack_int32_grow___o_2)
    _obstack_newchunk ();
  obstack_int32_grow___o1_1 = data;
}
void
collate_output___o_2 (void)
{
  obstack_int32_grow (&collate_output_extrapool, nwcs);
  struct obstack *__o = &collate_output_extrapool;
  int __len = nwcs;
  if (__o + __len > (struct obstack *) collate_output___o_2)
    _obstack_newchunk ();
  __o->next_free += __len;
  obstack_int32_grow (&collate_output_extrapool, collate_output_runp_6);
}