[middle-end/PR102359] Not add initialization for DECL_VALUE_EXPR variables with -ftrivial-auto-var-init

  Hi, 

This is the patch to fix this issue based on our discussion.

I have tested it on aarch64 with bootstrap and regtests. X86 bootstrap was done, regtests is ongoing.

Okay for trunk?

Thanks.

Qing

======================
From d349ef0145512efe7f9af2c6bbd01f636475bce3 Mon Sep 17 00:00:00 2001
From: qing zhao <qing.zhao@oracle.com>
Date: Mon, 4 Oct 2021 15:26:03 -0700
Subject: [PATCH] middle-end/102359 Not add initialization for variables that
 have been  initialized by FEs.

C++ FE creates proxy variables, which have associated DECL_VALUE_EXPR
and have been initialized by FE. For such auto variable, we should not
add initialization when -ftrivial-auto-var-init presents.

gcc/ChangeLog:

2021-10-04  qing zhao  <qing.zhao@oracle.com>

	* gimplify.c (is_decl_init_by_fe): New function.
	(gimplify_decl_expr): Not add initialization for an auto variable
	when it has been initialized by frontend.

gcc/testsuite/ChangeLog:

2021-10-04  qing zhao  <qing.zhao@oracle.com>

	* g++.dg/pr102359_1.C: New test.
	* g++.dg/pr102359_2.C: New test.
---
 gcc/gimplify.c                    | 21 ++++++++++++++++++++-
 gcc/testsuite/g++.dg/pr102359_1.C | 13 +++++++++++++
 gcc/testsuite/g++.dg/pr102359_2.C | 13 +++++++++++++
 3 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/pr102359_1.C
 create mode 100644 gcc/testsuite/g++.dg/pr102359_2.C
  

On Tue, 5 Oct 2021, Qing Zhao wrote:

> Hi, 
> 
> This is the patch to fix this issue based on our discussion.
> 
> I have tested it on aarch64 with bootstrap and regtests. X86 bootstrap was done, regtests is ongoing.
> 
> Okay for trunk?
> 
> Thanks.
> 
> Qing
> 
> ======================
> From d349ef0145512efe7f9af2c6bbd01f636475bce3 Mon Sep 17 00:00:00 2001
> From: qing zhao <qing.zhao@oracle.com>
> Date: Mon, 4 Oct 2021 15:26:03 -0700
> Subject: [PATCH] middle-end/102359 Not add initialization for variables that
>  have been  initialized by FEs.
> 
> C++ FE creates proxy variables, which have associated DECL_VALUE_EXPR
> and have been initialized by FE. For such auto variable, we should not
> add initialization when -ftrivial-auto-var-init presents.
> 
> gcc/ChangeLog:
> 
> 2021-10-04  qing zhao  <qing.zhao@oracle.com>
> 
> 	* gimplify.c (is_decl_init_by_fe): New function.
> 	(gimplify_decl_expr): Not add initialization for an auto variable
> 	when it has been initialized by frontend.
> 
> gcc/testsuite/ChangeLog:
> 
> 2021-10-04  qing zhao  <qing.zhao@oracle.com>
> 
> 	* g++.dg/pr102359_1.C: New test.
> 	* g++.dg/pr102359_2.C: New test.
> ---
>  gcc/gimplify.c                    | 21 ++++++++++++++++++++-
>  gcc/testsuite/g++.dg/pr102359_1.C | 13 +++++++++++++
>  gcc/testsuite/g++.dg/pr102359_2.C | 13 +++++++++++++
>  3 files changed, 46 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/g++.dg/pr102359_1.C
>  create mode 100644 gcc/testsuite/g++.dg/pr102359_2.C
> 
> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
> index b27776a..d6865ad 100644
> --- a/gcc/gimplify.c
> +++ b/gcc/gimplify.c
> @@ -1819,6 +1819,19 @@ gimple_add_padding_init_for_auto_var (tree decl, bool is_vla,
>    gimplify_seq_add_stmt (seq_p, call);
>  }
>  
> +/* Return true if the DECL is initialized by FE.
> +   If the VAR_DECL has DECL_VALUE_EXPR that was created by FE (usually C++FE),
> +   it's a proxy varaible, and FE already initializd the DECL_VALUE_EXPR of it.
> +*/
> +static bool
> +is_decl_init_by_fe (tree decl, bool is_created_by_fe)
> +{
> +  if (DECL_HAS_VALUE_EXPR_P (decl)
> +      && is_created_by_fe)
> +    return true;
> +  return false;
> +}
> +
>  /* Return true if the DECL need to be automaticly initialized by the
>     compiler.  */
>  static bool
> @@ -1871,8 +1884,13 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>    if (VAR_P (decl) && !DECL_EXTERNAL (decl))
>      {
>        tree init = DECL_INITIAL (decl);
> +      bool is_value_expr_created_by_fe = false;

no need for the = false, it's always initialized below.

>        bool is_vla = false;
>  
> +      /* Check whether a decl has FE created VALUE_EXPR here BEFORE 
> +	 gimplify_vla_decl creates VALUE_EXPR for vla decl.  */
> +      is_value_expr_created_by_fe = DECL_HAS_VALUE_EXPR_P (decl);

That looks a bit weird when looking at ...

> +
>        poly_uint64 size;
>        if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
>  	  || (!TREE_STATIC (decl)
> @@ -1934,7 +1952,8 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>        /* When there is no explicit initializer, if the user requested,
>  	 We should insert an artifical initializer for this automatic
>  	 variable.  */
> -      else if (is_var_need_auto_init (decl))
> +      else if (is_var_need_auto_init (decl)
> +	       && !is_decl_init_by_fe (decl, is_value_expr_created_by_fe))

... which just expands to

 if (DECL_HAS_VALUE_EXPR_P (decl) && DECL_HAS_VALUE_EXPR_P (decl))

can you please name 'is_value_expr_created_by_fe' as
'decl_had_value_expr_p' and check && !decl_had_value_expr_p here?
So sth like

diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index b27776af7c8..9013f385f13 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -1872,6 +1872,7 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
     {
       tree init = DECL_INITIAL (decl);
       bool is_vla = false;
+      bool decl_had_value_expr_p = DECL_HAS_VALUE_EXPR_P (decl);
 
       poly_uint64 size;
       if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
@@ -1934,7 +1935,8 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
       /* When there is no explicit initializer, if the user requested,
         We should insert an artifical initializer for this automatic
         variable.  */
-      else if (is_var_need_auto_init (decl))
+      else if (is_var_need_auto_init (decl)
+              && !decl_had_value_expr_p)
        {
          gimple_add_init_for_auto_var (decl,
                                        flag_auto_var_init,

OK with that change.

Thanks,
Richard.


>  	{
>  	  gimple_add_init_for_auto_var (decl,
>  					flag_auto_var_init,
> diff --git a/gcc/testsuite/g++.dg/pr102359_1.C b/gcc/testsuite/g++.dg/pr102359_1.C
> new file mode 100644
> index 0000000..da643cd
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/pr102359_1.C
> @@ -0,0 +1,13 @@
> +/* PR middle-end/102359 ICE gimplification failed since
> +   r12-3433-ga25e0b5e6ac8a77a.  */
> +/* { dg-do compile } */
> +/* { dg-options "-ftrivial-auto-var-init=zero" } */
> +/* { dg-require-effective-target c++17 } */
> +
> +struct A {
> +  double a = 111;
> +  auto foo() {
> +    return [*this] { return a; };
> +  }
> +};
> +int X = A{}.foo()();
> diff --git a/gcc/testsuite/g++.dg/pr102359_2.C b/gcc/testsuite/g++.dg/pr102359_2.C
> new file mode 100644
> index 0000000..d026d72
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/pr102359_2.C
> @@ -0,0 +1,13 @@
> +/* PR middle-end/102359 ICE gimplification failed since
> +   r12-3433-ga25e0b5e6ac8a77a.  */
> +/* { dg-do run} */
> +/* { dg-options "-ftrivial-auto-var-init=zero" } */
> +/* { dg-require-effective-target c++17 } */
> +
> +int main()
> +{
> + int i = 42;
> + auto l = [=]() mutable { return i; };
> + if (l() != i)
> +   __builtin_abort ();
> +}
>
  

> On Oct 5, 2021, at 3:19 AM, Richard Biener <rguenther@suse.de> wrote:
> 
> On Tue, 5 Oct 2021, Qing Zhao wrote:
> 
>> Hi, 
>> 
>> This is the patch to fix this issue based on our discussion.
>> 
>> I have tested it on aarch64 with bootstrap and regtests. X86 bootstrap was done, regtests is ongoing.
>> 
>> Okay for trunk?
>> 
>> Thanks.
>> 
>> Qing
>> 
>> ======================
>> From d349ef0145512efe7f9af2c6bbd01f636475bce3 Mon Sep 17 00:00:00 2001
>> From: qing zhao <qing.zhao@oracle.com>
>> Date: Mon, 4 Oct 2021 15:26:03 -0700
>> Subject: [PATCH] middle-end/102359 Not add initialization for variables that
>> have been  initialized by FEs.
>> 
>> C++ FE creates proxy variables, which have associated DECL_VALUE_EXPR
>> and have been initialized by FE. For such auto variable, we should not
>> add initialization when -ftrivial-auto-var-init presents.
>> 
>> gcc/ChangeLog:
>> 
>> 2021-10-04  qing zhao  <qing.zhao@oracle.com>
>> 
>> 	* gimplify.c (is_decl_init_by_fe): New function.
>> 	(gimplify_decl_expr): Not add initialization for an auto variable
>> 	when it has been initialized by frontend.
>> 
>> gcc/testsuite/ChangeLog:
>> 
>> 2021-10-04  qing zhao  <qing.zhao@oracle.com>
>> 
>> 	* g++.dg/pr102359_1.C: New test.
>> 	* g++.dg/pr102359_2.C: New test.
>> ---
>> gcc/gimplify.c                    | 21 ++++++++++++++++++++-
>> gcc/testsuite/g++.dg/pr102359_1.C | 13 +++++++++++++
>> gcc/testsuite/g++.dg/pr102359_2.C | 13 +++++++++++++
>> 3 files changed, 46 insertions(+), 1 deletion(-)
>> create mode 100644 gcc/testsuite/g++.dg/pr102359_1.C
>> create mode 100644 gcc/testsuite/g++.dg/pr102359_2.C
>> 
>> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
>> index b27776a..d6865ad 100644
>> --- a/gcc/gimplify.c
>> +++ b/gcc/gimplify.c
>> @@ -1819,6 +1819,19 @@ gimple_add_padding_init_for_auto_var (tree decl, bool is_vla,
>>   gimplify_seq_add_stmt (seq_p, call);
>> }
>> 
>> +/* Return true if the DECL is initialized by FE.
>> +   If the VAR_DECL has DECL_VALUE_EXPR that was created by FE (usually C++FE),
>> +   it's a proxy varaible, and FE already initializd the DECL_VALUE_EXPR of it.
>> +*/
>> +static bool
>> +is_decl_init_by_fe (tree decl, bool is_created_by_fe)
>> +{
>> +  if (DECL_HAS_VALUE_EXPR_P (decl)
>> +      && is_created_by_fe)
>> +    return true;
>> +  return false;
>> +}
>> +
>> /* Return true if the DECL need to be automaticly initialized by the
>>    compiler.  */
>> static bool
>> @@ -1871,8 +1884,13 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>>   if (VAR_P (decl) && !DECL_EXTERNAL (decl))
>>     {
>>       tree init = DECL_INITIAL (decl);
>> +      bool is_value_expr_created_by_fe = false;
> 
> no need for the = false, it's always initialized below.
> 
>>       bool is_vla = false;
>> 
>> +      /* Check whether a decl has FE created VALUE_EXPR here BEFORE 
>> +	 gimplify_vla_decl creates VALUE_EXPR for vla decl.  */
>> +      is_value_expr_created_by_fe = DECL_HAS_VALUE_EXPR_P (decl);
> 
> That looks a bit weird when looking at ...
> 
>> +
>>       poly_uint64 size;
>>       if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
>> 	  || (!TREE_STATIC (decl)
>> @@ -1934,7 +1952,8 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>>       /* When there is no explicit initializer, if the user requested,
>> 	 We should insert an artifical initializer for this automatic
>> 	 variable.  */
>> -      else if (is_var_need_auto_init (decl))
>> +      else if (is_var_need_auto_init (decl)
>> +	       && !is_decl_init_by_fe (decl, is_value_expr_created_by_fe))
> 
> ... which just expands to
> 
> if (DECL_HAS_VALUE_EXPR_P (decl) && DECL_HAS_VALUE_EXPR_P (decl))
> 
> can you please name 'is_value_expr_created_by_fe' as
> 'decl_had_value_expr_p' and check && !decl_had_value_expr_p here?
> So sth like

I can do this -:) I agree that the change will make the code simpler.

However, my major concern with this change is: later when people look at this change, they might ask:
Why we should not initialize a variable with VALUE_EXPR? And whether the variable whose VALUE_EXPR 
was created by “gimplify_vla_decl” should be excluded? 

My new function and comments were all for this purpose.

If I go with this change, at least we should add some comments to explain this as following, what do you think?
> 
> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
> index b27776af7c8..9013f385f13 100644
> --- a/gcc/gimplify.c
> +++ b/gcc/gimplify.c
> @@ -1872,6 +1872,7 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>     {
>       tree init = DECL_INITIAL (decl);
>       bool is_vla = false;

   + /* Check whether a decl has FE created VALUE_EXPR here BEFORE 
   +	 gimplify_vla_decl creates VALUE_EXPR for vla decl.  */

> +      bool decl_had_value_expr_p = DECL_HAS_VALUE_EXPR_P (decl);
> 
>       poly_uint64 size;
>       if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
> @@ -1934,7 +1935,8 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>       /* When there is no explicit initializer, if the user requested,
>         We should insert an artifical initializer for this automatic
>         variable.  */
> -      else if (is_var_need_auto_init (decl))
> +      else if (is_var_need_auto_init (decl)

+   /* If the VAR_DECL has DECL_VALUE_EXPR that was created by FE (usually C++FE),
+   it's a proxy varaible, and FE already initializd the DECL_VALUE_EXPR of it. */

> +              && !decl_had_value_expr_p)
>        {
>          gimple_add_init_for_auto_var (decl,
>                                        flag_auto_var_init,
> 
> OK with that change.

thanks.

Qing
> 
> Thanks,
> Richard.
> 
> 
>> 	{
>> 	  gimple_add_init_for_auto_var (decl,
>> 					flag_auto_var_init,
>> diff --git a/gcc/testsuite/g++.dg/pr102359_1.C b/gcc/testsuite/g++.dg/pr102359_1.C
>> new file mode 100644
>> index 0000000..da643cd
>> --- /dev/null
>> +++ b/gcc/testsuite/g++.dg/pr102359_1.C
>> @@ -0,0 +1,13 @@
>> +/* PR middle-end/102359 ICE gimplification failed since
>> +   r12-3433-ga25e0b5e6ac8a77a.  */
>> +/* { dg-do compile } */
>> +/* { dg-options "-ftrivial-auto-var-init=zero" } */
>> +/* { dg-require-effective-target c++17 } */
>> +
>> +struct A {
>> +  double a = 111;
>> +  auto foo() {
>> +    return [*this] { return a; };
>> +  }
>> +};
>> +int X = A{}.foo()();
>> diff --git a/gcc/testsuite/g++.dg/pr102359_2.C b/gcc/testsuite/g++.dg/pr102359_2.C
>> new file mode 100644
>> index 0000000..d026d72
>> --- /dev/null
>> +++ b/gcc/testsuite/g++.dg/pr102359_2.C
>> @@ -0,0 +1,13 @@
>> +/* PR middle-end/102359 ICE gimplification failed since
>> +   r12-3433-ga25e0b5e6ac8a77a.  */
>> +/* { dg-do run} */
>> +/* { dg-options "-ftrivial-auto-var-init=zero" } */
>> +/* { dg-require-effective-target c++17 } */
>> +
>> +int main()
>> +{
>> + int i = 42;
>> + auto l = [=]() mutable { return i; };
>> + if (l() != i)
>> +   __builtin_abort ();
>> +}
>> 
> 
> -- 
> Richard Biener <rguenther@suse.de>
> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
> Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
  

This is the updated patch, I will push it after done with testing.

Let me know if you see any issue.

Thanks.

Qing.

============================

From 1f07c20ecdc9a015369c8bb472ebbd3bcaabdf17 Mon Sep 17 00:00:00 2001
From: qing zhao <qing.zhao@oracle.com>
Date: Tue, 5 Oct 2021 08:10:02 -0700
Subject: [PATCH] middle-end/102359 Not add initialization for variables that
 have been  initialized by FEs.

C++ FE creates proxy variables, which have associated DECL_VALUE_EXPR
and have been initialized by FE. For such auto variable, we should not
add initialization when -ftrivial-auto-var-init presents.

gcc/ChangeLog:

2021-10-05  qing zhao  <qing.zhao@oracle.com>

	* gimplify.c (gimplify_decl_expr): Not add initialization for an
	auto variable when it has been initialized by frontend.

gcc/testsuite/ChangeLog:

2021-10-05  qing zhao  <qing.zhao@oracle.com>

	* g++.dg/pr102359_1.C: New test.
	* g++.dg/pr102359_2.C: New test.
---
 gcc/gimplify.c                    |  9 ++++++++-
 gcc/testsuite/g++.dg/pr102359_1.C | 13 +++++++++++++
 gcc/testsuite/g++.dg/pr102359_2.C | 13 +++++++++++++
 3 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/pr102359_1.C
 create mode 100644 gcc/testsuite/g++.dg/pr102359_2.C

diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index b27776a..d96fca4 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -1872,6 +1872,9 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
     {
       tree init = DECL_INITIAL (decl);
       bool is_vla = false;
+      /* Check whether a decl has FE created VALUE_EXPR here BEFORE
+	 gimplify_vla_decl creates VALUE_EXPR for a vla decl.  */
+      bool decl_had_value_expr_p = DECL_HAS_VALUE_EXPR_P (decl);
 
       poly_uint64 size;
       if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
@@ -1934,7 +1937,11 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
       /* When there is no explicit initializer, if the user requested,
 	 We should insert an artifical initializer for this automatic
 	 variable.  */
-      else if (is_var_need_auto_init (decl))
+      else if (is_var_need_auto_init (decl)
+	       /* If the decl has VALUE_EXPR that was created by FE (usually
+		  C++FE), it's a proxy varaible, and FE already initialized
+		  the VALUE_EXPR of it, we should not initialize it here.  */
+	       && !decl_had_value_expr_p)
 	{
 	  gimple_add_init_for_auto_var (decl,
 					flag_auto_var_init,
diff --git a/gcc/testsuite/g++.dg/pr102359_1.C b/gcc/testsuite/g++.dg/pr102359_1.C
new file mode 100644
index 0000000..da643cd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr102359_1.C
@@ -0,0 +1,13 @@
+/* PR middle-end/102359 ICE gimplification failed since
+   r12-3433-ga25e0b5e6ac8a77a.  */
+/* { dg-do compile } */
+/* { dg-options "-ftrivial-auto-var-init=zero" } */
+/* { dg-require-effective-target c++17 } */
+
+struct A {
+  double a = 111;
+  auto foo() {
+    return [*this] { return a; };
+  }
+};
+int X = A{}.foo()();
diff --git a/gcc/testsuite/g++.dg/pr102359_2.C b/gcc/testsuite/g++.dg/pr102359_2.C
new file mode 100644
index 0000000..d026d72
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr102359_2.C
@@ -0,0 +1,13 @@
+/* PR middle-end/102359 ICE gimplification failed since
+   r12-3433-ga25e0b5e6ac8a77a.  */
+/* { dg-do run} */
+/* { dg-options "-ftrivial-auto-var-init=zero" } */
+/* { dg-require-effective-target c++17 } */
+
+int main()
+{
+ int i = 42;
+ auto l = [=]() mutable { return i; };
+ if (l() != i)
+   __builtin_abort ();
+}
  

On 10/5/21 10:32, Qing Zhao wrote:
> 
> 
>> On Oct 5, 2021, at 3:19 AM, Richard Biener <rguenther@suse.de> wrote:
>>
>> On Tue, 5 Oct 2021, Qing Zhao wrote:
>>
>>> Hi,
>>>
>>> This is the patch to fix this issue based on our discussion.
>>>
>>> I have tested it on aarch64 with bootstrap and regtests. X86 bootstrap was done, regtests is ongoing.
>>>
>>> Okay for trunk?
>>>
>>> Thanks.
>>>
>>> Qing
>>>
>>> ======================
>>>  From d349ef0145512efe7f9af2c6bbd01f636475bce3 Mon Sep 17 00:00:00 2001
>>> From: qing zhao <qing.zhao@oracle.com>
>>> Date: Mon, 4 Oct 2021 15:26:03 -0700
>>> Subject: [PATCH] middle-end/102359 Not add initialization for variables that
>>> have been  initialized by FEs.
>>>
>>> C++ FE creates proxy variables, which have associated DECL_VALUE_EXPR
>>> and have been initialized by FE. For such auto variable, we should not
>>> add initialization when -ftrivial-auto-var-init presents.
>>>
>>> gcc/ChangeLog:
>>>
>>> 2021-10-04  qing zhao  <qing.zhao@oracle.com>
>>>
>>> 	* gimplify.c (is_decl_init_by_fe): New function.
>>> 	(gimplify_decl_expr): Not add initialization for an auto variable
>>> 	when it has been initialized by frontend.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> 2021-10-04  qing zhao  <qing.zhao@oracle.com>
>>>
>>> 	* g++.dg/pr102359_1.C: New test.
>>> 	* g++.dg/pr102359_2.C: New test.
>>> ---
>>> gcc/gimplify.c                    | 21 ++++++++++++++++++++-
>>> gcc/testsuite/g++.dg/pr102359_1.C | 13 +++++++++++++
>>> gcc/testsuite/g++.dg/pr102359_2.C | 13 +++++++++++++
>>> 3 files changed, 46 insertions(+), 1 deletion(-)
>>> create mode 100644 gcc/testsuite/g++.dg/pr102359_1.C
>>> create mode 100644 gcc/testsuite/g++.dg/pr102359_2.C
>>>
>>> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
>>> index b27776a..d6865ad 100644
>>> --- a/gcc/gimplify.c
>>> +++ b/gcc/gimplify.c
>>> @@ -1819,6 +1819,19 @@ gimple_add_padding_init_for_auto_var (tree decl, bool is_vla,
>>>    gimplify_seq_add_stmt (seq_p, call);
>>> }
>>>
>>> +/* Return true if the DECL is initialized by FE.
>>> +   If the VAR_DECL has DECL_VALUE_EXPR that was created by FE (usually C++FE),
>>> +   it's a proxy varaible, and FE already initializd the DECL_VALUE_EXPR of it.
>>> +*/
>>> +static bool
>>> +is_decl_init_by_fe (tree decl, bool is_created_by_fe)
>>> +{
>>> +  if (DECL_HAS_VALUE_EXPR_P (decl)
>>> +      && is_created_by_fe)
>>> +    return true;
>>> +  return false;
>>> +}
>>> +
>>> /* Return true if the DECL need to be automaticly initialized by the
>>>     compiler.  */
>>> static bool
>>> @@ -1871,8 +1884,13 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>>>    if (VAR_P (decl) && !DECL_EXTERNAL (decl))
>>>      {
>>>        tree init = DECL_INITIAL (decl);
>>> +      bool is_value_expr_created_by_fe = false;
>>
>> no need for the = false, it's always initialized below.
>>
>>>        bool is_vla = false;
>>>
>>> +      /* Check whether a decl has FE created VALUE_EXPR here BEFORE
>>> +	 gimplify_vla_decl creates VALUE_EXPR for vla decl.  */
>>> +      is_value_expr_created_by_fe = DECL_HAS_VALUE_EXPR_P (decl);
>>
>> That looks a bit weird when looking at ...
>>
>>> +
>>>        poly_uint64 size;
>>>        if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
>>> 	  || (!TREE_STATIC (decl)
>>> @@ -1934,7 +1952,8 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>>>        /* When there is no explicit initializer, if the user requested,
>>> 	 We should insert an artifical initializer for this automatic
>>> 	 variable.  */
>>> -      else if (is_var_need_auto_init (decl))
>>> +      else if (is_var_need_auto_init (decl)
>>> +	       && !is_decl_init_by_fe (decl, is_value_expr_created_by_fe))
>>
>> ... which just expands to
>>
>> if (DECL_HAS_VALUE_EXPR_P (decl) && DECL_HAS_VALUE_EXPR_P (decl))
>>
>> can you please name 'is_value_expr_created_by_fe' as
>> 'decl_had_value_expr_p' and check && !decl_had_value_expr_p here?
>> So sth like
> 
> I can do this -:) I agree that the change will make the code simpler.
> 
> However, my major concern with this change is: later when people look at this change, they might ask:
> Why we should not initialize a variable with VALUE_EXPR? And whether the variable whose VALUE_EXPR
> was created by “gimplify_vla_decl” should be excluded?
> 
> My new function and comments were all for this purpose.
> 
> If I go with this change, at least we should add some comments to explain this as following, what do you think?
>>
>> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
>> index b27776af7c8..9013f385f13 100644
>> --- a/gcc/gimplify.c
>> +++ b/gcc/gimplify.c
>> @@ -1872,6 +1872,7 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>>      {
>>        tree init = DECL_INITIAL (decl);
>>        bool is_vla = false;
> 
>     + /* Check whether a decl has FE created VALUE_EXPR here BEFORE
>     +	 gimplify_vla_decl creates VALUE_EXPR for vla decl.  */
>> +      bool decl_had_value_expr_p = DECL_HAS_VALUE_EXPR_P (decl);
>>
>>        poly_uint64 size;
>>        if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
>> @@ -1934,7 +1935,8 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>>        /* When there is no explicit initializer, if the user requested,
>>          We should insert an artifical initializer for this automatic
>>          variable.  */
>> -      else if (is_var_need_auto_init (decl))
>> +      else if (is_var_need_auto_init (decl)
> 
> +   /* If the VAR_DECL has DECL_VALUE_EXPR that was created by FE (usually C++FE),
> +   it's a proxy varaible, and FE already initializd the DECL_VALUE_EXPR of it. */

I'd suggest merging this comment into the comment on the variable 
declaration.

>> +              && !decl_had_value_expr_p)
>>         {
>>           gimple_add_init_for_auto_var (decl,
>>                                         flag_auto_var_init,
>>
>> OK with that change.
> 
> thanks.
> 
> Qing
>>
>> Thanks,
>> Richard.
>>
>>
>>> 	{
>>> 	  gimple_add_init_for_auto_var (decl,
>>> 					flag_auto_var_init,
>>> diff --git a/gcc/testsuite/g++.dg/pr102359_1.C b/gcc/testsuite/g++.dg/pr102359_1.C
>>> new file mode 100644
>>> index 0000000..da643cd
>>> --- /dev/null
>>> +++ b/gcc/testsuite/g++.dg/pr102359_1.C
>>> @@ -0,0 +1,13 @@
>>> +/* PR middle-end/102359 ICE gimplification failed since
>>> +   r12-3433-ga25e0b5e6ac8a77a.  */
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-ftrivial-auto-var-init=zero" } */
>>> +/* { dg-require-effective-target c++17 } */
>>> +
>>> +struct A {
>>> +  double a = 111;
>>> +  auto foo() {
>>> +    return [*this] { return a; };
>>> +  }
>>> +};
>>> +int X = A{}.foo()();
>>> diff --git a/gcc/testsuite/g++.dg/pr102359_2.C b/gcc/testsuite/g++.dg/pr102359_2.C
>>> new file mode 100644
>>> index 0000000..d026d72
>>> --- /dev/null
>>> +++ b/gcc/testsuite/g++.dg/pr102359_2.C
>>> @@ -0,0 +1,13 @@
>>> +/* PR middle-end/102359 ICE gimplification failed since
>>> +   r12-3433-ga25e0b5e6ac8a77a.  */
>>> +/* { dg-do run} */
>>> +/* { dg-options "-ftrivial-auto-var-init=zero" } */
>>> +/* { dg-require-effective-target c++17 } */
>>> +
>>> +int main()
>>> +{
>>> + int i = 42;
>>> + auto l = [=]() mutable { return i; };
>>> + if (l() != i)
>>> +   __builtin_abort ();
>>> +}
>>>
>>
>> -- 
>> Richard Biener <rguenther@suse.de>
>> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
>> Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
>
  

> On Oct 5, 2021, at 1:30 PM, Jason Merrill <jason@redhat.com> wrote:
> 
>>> 'decl_had_value_expr_p' and check && !decl_had_value_expr_p here?
>>> So sth like
>> I can do this -:) I agree that the change will make the code simpler.
>> However, my major concern with this change is: later when people look at this change, they might ask:
>> Why we should not initialize a variable with VALUE_EXPR? And whether the variable whose VALUE_EXPR
>> was created by “gimplify_vla_decl” should be excluded?
>> My new function and comments were all for this purpose.
>> If I go with this change, at least we should add some comments to explain this as following, what do you think?
>>> 
>>> diff --git a/gcc/gimplify.c b/gcc/gimplify.c
>>> index b27776af7c8..9013f385f13 100644
>>> --- a/gcc/gimplify.c
>>> +++ b/gcc/gimplify.c
>>> @@ -1872,6 +1872,7 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>>>     {
>>>       tree init = DECL_INITIAL (decl);
>>>       bool is_vla = false;
>>    + /* Check whether a decl has FE created VALUE_EXPR here BEFORE
>>    +	 gimplify_vla_decl creates VALUE_EXPR for vla decl.  */
>>> +      bool decl_had_value_expr_p = DECL_HAS_VALUE_EXPR_P (decl);
>>> 
>>>       poly_uint64 size;
>>>       if (!poly_int_tree_p (DECL_SIZE_UNIT (decl), &size)
>>> @@ -1934,7 +1935,8 @@ gimplify_decl_expr (tree *stmt_p, gimple_seq *seq_p)
>>>       /* When there is no explicit initializer, if the user requested,
>>>         We should insert an artifical initializer for this automatic
>>>         variable.  */
>>> -      else if (is_var_need_auto_init (decl))
>>> +      else if (is_var_need_auto_init (decl)
>> +   /* If the VAR_DECL has DECL_VALUE_EXPR that was created by FE (usually C++FE),
>> +   it's a proxy varaible, and FE already initializd the DECL_VALUE_EXPR of it. */
> 
> I'd suggest merging this comment into the comment on the variable declaration.

Okay, will merge these two comments into one and put it on the variable declaration.

thanks.

Qing