[Bug c++/111026] New: Incorrect optimization with -o2,-o

[Bug c++/111026] New: Incorrect optimization with -o2,-o

[zhaiqiming at baidu dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111026

            Bug ID: 111026
           Summary: Incorrect optimization with -o2,-o
           Product: gcc
           Version: 12.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zhaiqiming at baidu dot com
  Target Milestone: ---

[Bug c++/111026] Incorrect optimization with -o2,-o

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111026

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-08-15
             Status|UNCONFIRMED                 |WAITING

[Bug c++/111026] Incorrect optimization with -o2,-o

[zhaiqiming at baidu dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111026

--- Comment #1 from zhaiqiming at baidu dot com ---
======

[summary]

When I upgraded from gcc82 to gcc12, I found that linked_list_t::del execution
did not meet expectations. 
Looking at .s , i noticed that the assembly statements corresponding to the
following two lines have disappeared.

(node.*list_node).next->prev = (node.*list_node).prev;
(node.*list_node).prev->next = (node.*list_node).next;


======

[environment-gcc12]
Reading specs from
/home/opt/compiler/gcc-12/bin/../lib/gcc/x86_64-pc-linux-gnu/12.1.0/specs
COLLECT_GCC=/home/opt/compiler/gcc-12/bin/gcc
COLLECT_LTO_WRAPPER=/home/opt/compiler/gcc-12/bin/../libexec/gcc/x86_64-pc-linux-gnu/12.1.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --prefix=/opt/compiler/gcc-12
--with-local-prefix=/opt/compiler/gcc-12
--with-native-system-header-dir=/opt/compiler/gcc-12/include
--enable-languages=c,c++ --disable-libstdcxx-pch --disable-multilib
--with-default-libstdcxx-abi=gcc4-compatible --disable-bootstrap
--with-sysroot=/ --build=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu
--enable-gold --enable-lto
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.1.0 (GCC) 

[environment-gcc82]
Using built-in specs.
COLLECT_GCC=/home/opt/compiler/gcc-8.2/gcc-8.2/bin/gcc
COLLECT_LTO_WRAPPER=/home/opt/compiler/gcc-8.2/gcc-8.2/bin/../libexec/gcc/x86_64-pc-linux-gnu/8.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --prefix=/opt/compiler/gcc-8.2
--with-local-prefix=/opt/compiler/gcc-8.2
--with-native-system-header-dir=/opt/compiler/gcc-8.2/include
--enable-languages=c,c++ --disable-libstdcxx-pch --disable-multilib
--disable-bootstrap --with-default-libstdcxx-abi=gcc4-compatible
Thread model: posix
gcc version 8.2.0 (GCC) 

======

[source code]


struct list_node_t
{
        list_node_t *next;
        list_node_t *prev;
};

template <typename T, list_node_t T::*inner_list_node>
class list_t
{
        public:
                list_t() { _head.next = _head.prev = &_head; }
                bool is_empty() const { return _head.next == &_head; }
                T* entry(list_node_t &node) const { return &node == &_head ?
NULL : (T*)((char*)&node - (char*)_node_offset); }

                void add(T &node)
                {
                        _head.next->prev = &(node.*inner_list_node);
                        (node.*inner_list_node).next = _head.next;
                        (node.*inner_list_node).prev = &_head;
                        _head.next = &(node.*inner_list_node);
                }


                static void del(T &node)
                {
            int slot_1 = 10000;
            printf("slot_1 %d\n", slot_1);
                        (node.*inner_list_node).next->prev =
(node.*inner_list_node).prev;
                        (node.*inner_list_node).prev->next =
(node.*inner_list_node).next;
                        int slot_2 = 20000;
            printf("slot_2 %d\n", slot_2);
                }

        protected:
                static list_node_t const * const _node_offset;
                list_node_t _head;
};
template <typename T, list_node_t T::*inner_list_node>
list_node_t const * const list_t<T, inner_list_node>::_node_offset = &(((T
*)0)->*inner_list_node);

template <typename T, list_node_t T::*inner_list_node>
class safe_list_t: public list_t<T, inner_list_node>
{
        public:
                safe_list_t(): _alive(1),_num(0)
        {
                pthread_mutex_init(&_mutex, NULL);
                pthread_cond_init(&_cond, NULL);
        }

                ~safe_list_t()
                {
                        pthread_cond_destroy(&_cond);
                        pthread_mutex_destroy(&_mutex);
                }

                int len()
                {
                        return _num;
                }

                void put(T &node)
                {
                        pthread_mutex_lock(&_mutex);
                        if (_alive)
                        {
                this->add(node);
                                ++_num;
                        }
                        pthread_mutex_unlock(&_mutex);
                        pthread_cond_signal(&_cond);
                }

                T* get()
                {
                        T *ret;
                        pthread_mutex_lock(&_mutex);
                        while (_alive && list_t<T,
inner_list_node>::is_empty())
                                pthread_cond_wait(&_cond, &_mutex);
                        if (_alive)
                        {
                ret = this->entry(*list_t<T, inner_list_node>::_head.prev);
                this->del(*ret);
                                --_num;
                        }
                        else
                        {
                                ret = NULL;
                        }
                        pthread_mutex_unlock(&_mutex);
                        return ret;
                }

        protected:
                pthread_mutex_t _mutex;
                pthread_cond_t _cond;
                int _alive;
                int _num;
};

template <class T>
class worker_t
{
public:
    T *t;
    list_node_t inner_task_list_node;

public:
    worker_t():t(NULL)
    {
        t = new T;
    }
    worker_t(T *tt):t(tt)
    {
    }

    ~worker_t()
    {
        delete t;
    }

private:
    worker_t(const worker_t& rhs);
    worker_t& operator=(const worker_t& rhs);
};

int main() {
    safe_list_t<worker_t<size_t>, &worker_t<size_t>::inner_task_list_node>  
_serialize_merge_scan_move_list;

    auto * worker_0 = new worker_t<size_t>;
    *worker_0->t = 100;
    _serialize_merge_scan_move_list.put(*worker_0);

    auto * worker_1 = new worker_t<size_t>;
    *worker_1->t = 200;
    _serialize_merge_scan_move_list.put(*worker_1);

    auto* temp_0 = _serialize_merge_scan_move_list.get();
    printf("temp_0->t = %zu\n", *temp_0->t);
    delete temp_0;


    auto* temp_1 = _serialize_merge_scan_move_list.get();
    printf("temp_1->t = %zu\n", *temp_1->t);
    delete temp_1;
}


=====

[.s]

[important parts - gcc82]
Shell command: /home/opt/compiler/gcc-8.2/gcc-8.2/bin/gcc  -S -ohello82-use.s  
-save-temps -std=c++11 -O2 -pipe  -Wall -Wextra  -W  -fPIC
-Werror=return-local-addr -Werror=return-type test_main.cpp -lstdc++  -lpthread
-lssl -lcrypto -lrt -lz -ldl


.L8:
        .cfi_restore_state
        movq    8(%rbx), %r12
        cmpq    %rbx, %r12
        je      .L15
        movq   
_ZN6list_tI8worker_tImEXadL_ZNS1_20inner_task_list_nodeEEEE12_node_offsetE@GOTPCREL(%rip),
%rax
        movl    $10000, %esi
        leaq    .LC0(%rip), %rdi
        subq    (%rax), %r12
        xorl    %eax, %eax
        call    printf@PLT
        movq    8(%r12), %rdx
        movq    16(%r12), %rax
        movl    $20000, %esi
        leaq    .LC1(%rip), %rdi
        movq    %rax, 8(%rdx)
        movq    %rdx, (%rax)
        xorl    %eax, %eax
        call    printf@PLT
        subl    $1, 108(%rbx)
        movq    %rbp, %rdi
        call    pthread_mutex_unlock@PLT
        movq    %r12, %rax
        popq    %rbx
        .cfi_remember_state
        .cfi_def_cfa_offset 24
        popq    %rbp
        .cfi_def_cfa_offset 16
        popq    %r12
        .cfi_def_cfa_offset 8
        ret


[important parts - gcc12]
Shell command: /home/opt/compiler/gcc-12/bin/gcc  -S -ohello12-use.s  
-save-temps -std=c++11 -O2 -pipe  -Wall -Wextra  -W  -fPIC
-Werror=return-local-addr -Werror=return-type test_main.cpp -lstdc++  -lpthread
-lssl -lcrypto -lrt -lz -ldl


.L11:
        movl    $10000, %esi
        leaq    .LC0(%rip), %rdi
        xorl    %eax, %eax
        call    printf@PLT
        movl    $20000, %esi
        leaq    .LC1(%rip), %rdi
        xorl    %eax, %eax
        call    printf@PLT
        subl    $1, 108(%rbx)
        movq    %rbp, %rdi
        call    pthread_mutex_unlock@PLT
        movq    %r12, %rax
        popq    %rbx
        .cfi_remember_state
        .cfi_def_cfa_offset 24
        popq    %rbp
        .cfi_def_cfa_offset 16
        popq    %r12
        .cfi_def_cfa_offset 8
        ret
        .p2align 4,,10
        .p2align 3

[Bug c++/111026] Incorrect optimization with -o1,-o2

[zhaiqiming at baidu dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111026

--- Comment #2 from zhaiqiming at baidu dot com ---
(In reply to zhaiqiming from comment #1)
> ======
> 
> [summary]
> 
> When I upgraded from gcc82 to gcc12, I found that linked_list_t::del
> execution did not meet expectations. 
> Looking at .s , i noticed that the assembly statements corresponding to the
> following two lines have disappeared.
> 
> (node.*list_node).next->prev = (node.*list_node).prev;
> (node.*list_node).prev->next = (node.*list_node).next;
> 
> 
> ======
> 
> [environment-gcc12]
> Reading specs from
> /home/opt/compiler/gcc-12/bin/../lib/gcc/x86_64-pc-linux-gnu/12.1.0/specs
> COLLECT_GCC=/home/opt/compiler/gcc-12/bin/gcc
> COLLECT_LTO_WRAPPER=/home/opt/compiler/gcc-12/bin/../libexec/gcc/x86_64-pc-
> linux-gnu/12.1.0/lto-wrapper
> Target: x86_64-pc-linux-gnu
> Configured with: ../configure --prefix=/opt/compiler/gcc-12
> --with-local-prefix=/opt/compiler/gcc-12
> --with-native-system-header-dir=/opt/compiler/gcc-12/include
> --enable-languages=c,c++ --disable-libstdcxx-pch --disable-multilib
> --with-default-libstdcxx-abi=gcc4-compatible --disable-bootstrap
> --with-sysroot=/ --build=x86_64-pc-linux-gnu --target=x86_64-pc-linux-gnu
> --enable-gold --enable-lto
> Thread model: posix
> Supported LTO compression algorithms: zlib
> gcc version 12.1.0 (GCC) 
> 
> [environment-gcc82]
> Using built-in specs.
> COLLECT_GCC=/home/opt/compiler/gcc-8.2/gcc-8.2/bin/gcc
> COLLECT_LTO_WRAPPER=/home/opt/compiler/gcc-8.2/gcc-8.2/bin/../libexec/gcc/
> x86_64-pc-linux-gnu/8.2.0/lto-wrapper
> Target: x86_64-pc-linux-gnu
> Configured with: ../configure --prefix=/opt/compiler/gcc-8.2
> --with-local-prefix=/opt/compiler/gcc-8.2
> --with-native-system-header-dir=/opt/compiler/gcc-8.2/include
> --enable-languages=c,c++ --disable-libstdcxx-pch --disable-multilib
> --disable-bootstrap --with-default-libstdcxx-abi=gcc4-compatible
> Thread model: posix
> gcc version 8.2.0 (GCC) 
> 
> ======
> 
> [source code]
> 
> 
> struct list_node_t
> {
> 	list_node_t *next;
> 	list_node_t *prev;
> };
> 
> template <typename T, list_node_t T::*inner_list_node>
> class list_t
> {
> 	public:
> 		list_t() { _head.next = _head.prev = &_head; }
> 		bool is_empty() const { return _head.next == &_head; }
> 		T* entry(list_node_t &node) const { return &node == &_head ? NULL :
> (T*)((char*)&node - (char*)_node_offset); }
> 
> 		void add(T &node)
> 		{
> 			_head.next->prev = &(node.*inner_list_node);
> 			(node.*inner_list_node).next = _head.next;
> 			(node.*inner_list_node).prev = &_head;
> 			_head.next = &(node.*inner_list_node);
> 		}
> 
> 
> 		static void del(T &node)
> 		{
>             int slot_1 = 10000;
>             printf("slot_1 %d\n", slot_1);
> 			(node.*inner_list_node).next->prev = (node.*inner_list_node).prev;
> 			(node.*inner_list_node).prev->next = (node.*inner_list_node).next;
> 			int slot_2 = 20000;
>             printf("slot_2 %d\n", slot_2);
> 		}
> 
> 	protected:
> 		static list_node_t const * const _node_offset;
> 		list_node_t _head;
> };
> template <typename T, list_node_t T::*inner_list_node>
> list_node_t const * const list_t<T, inner_list_node>::_node_offset = &(((T
> *)0)->*inner_list_node);
> 
> template <typename T, list_node_t T::*inner_list_node>
> class safe_list_t: public list_t<T, inner_list_node>
> {
> 	public:
> 		safe_list_t(): _alive(1),_num(0)
> 	{
> 		pthread_mutex_init(&_mutex, NULL);
> 		pthread_cond_init(&_cond, NULL);
> 	}
> 
> 		~safe_list_t()
> 		{
> 			pthread_cond_destroy(&_cond);
> 			pthread_mutex_destroy(&_mutex);
> 		}
> 
> 		int len()
> 		{
> 			return _num;
> 		}
> 
> 		void put(T &node)
> 		{
> 			pthread_mutex_lock(&_mutex);
> 			if (_alive)
> 			{
>                 this->add(node);
> 				++_num;
> 			}
> 			pthread_mutex_unlock(&_mutex);
> 			pthread_cond_signal(&_cond);
> 		}
> 
> 		T* get()
> 		{
> 			T *ret;
> 			pthread_mutex_lock(&_mutex);
> 			while (_alive && list_t<T, inner_list_node>::is_empty())
> 				pthread_cond_wait(&_cond, &_mutex);
> 			if (_alive)
> 			{
>                 ret = this->entry(*list_t<T, inner_list_node>::_head.prev);
>                 this->del(*ret);
> 				--_num;
> 			}
> 			else
> 			{
> 				ret = NULL;
> 			}
> 			pthread_mutex_unlock(&_mutex);
> 			return ret;
> 		}
> 
> 	protected:
> 		pthread_mutex_t _mutex;
> 		pthread_cond_t _cond;
> 		int _alive;
> 		int _num;
> };
> 
> template <class T>
> class worker_t
> {
> public:
>     T *t;
>     list_node_t inner_task_list_node;
> 
> public:
>     worker_t():t(NULL)
>     {
>         t = new T;
>     }
>     worker_t(T *tt):t(tt)
>     {
>     }
> 
>     ~worker_t()
>     {
>         delete t;
>     }
>  
> private:
>     worker_t(const worker_t& rhs);
>     worker_t& operator=(const worker_t& rhs);
> };
> 
> int main() {
>     safe_list_t<worker_t<size_t>, &worker_t<size_t>::inner_task_list_node>  
> _serialize_merge_scan_move_list;
> 
>     auto * worker_0 = new worker_t<size_t>;
>     *worker_0->t = 100;
>     _serialize_merge_scan_move_list.put(*worker_0);
> 
>     auto * worker_1 = new worker_t<size_t>;
>     *worker_1->t = 200;
>     _serialize_merge_scan_move_list.put(*worker_1);
> 
>     auto* temp_0 = _serialize_merge_scan_move_list.get();
>     printf("temp_0->t = %zu\n", *temp_0->t);
>     delete temp_0;
> 
>     
>     auto* temp_1 = _serialize_merge_scan_move_list.get();
>     printf("temp_1->t = %zu\n", *temp_1->t);
>     delete temp_1;
> }
> 
> 
> =====
> 
> [.s]
> 
> [important parts - gcc82]
> Shell command: /home/opt/compiler/gcc-8.2/gcc-8.2/bin/gcc  -S
> -ohello82-use.s   -save-temps -std=c++11 -O2 -pipe  -Wall -Wextra  -W  -fPIC
> -Werror=return-local-addr -Werror=return-type test_main.cpp -lstdc++ 
> -lpthread -lssl -lcrypto -lrt -lz -ldl
> 
> 
> .L8:
> 	.cfi_restore_state
> 	movq	8(%rbx), %r12
> 	cmpq	%rbx, %r12
> 	je	.L15
> 	movq
> _ZN6list_tI8worker_tImEXadL_ZNS1_20inner_task_list_nodeEEEE12_node_offsetE@GO
> TPCREL(%rip), %rax
> 	movl	$10000, %esi
> 	leaq	.LC0(%rip), %rdi
> 	subq	(%rax), %r12
> 	xorl	%eax, %eax
> 	call	printf@PLT
> 	movq	8(%r12), %rdx
> 	movq	16(%r12), %rax
> 	movl	$20000, %esi
> 	leaq	.LC1(%rip), %rdi
> 	movq	%rax, 8(%rdx)
> 	movq	%rdx, (%rax)
> 	xorl	%eax, %eax
> 	call	printf@PLT
> 	subl	$1, 108(%rbx)
> 	movq	%rbp, %rdi
> 	call	pthread_mutex_unlock@PLT
> 	movq	%r12, %rax
> 	popq	%rbx
> 	.cfi_remember_state
> 	.cfi_def_cfa_offset 24
> 	popq	%rbp
> 	.cfi_def_cfa_offset 16
> 	popq	%r12
> 	.cfi_def_cfa_offset 8
> 	ret
> 
> 
> [important parts - gcc12]
> Shell command: /home/opt/compiler/gcc-12/bin/gcc  -S -ohello12-use.s  
> -save-temps -std=c++11 -O2 -pipe  -Wall -Wextra  -W  -fPIC
> -Werror=return-local-addr -Werror=return-type test_main.cpp -lstdc++ 
> -lpthread -lssl -lcrypto -lrt -lz -ldl
> 
> 
> .L11:
> 	movl	$10000, %esi
> 	leaq	.LC0(%rip), %rdi
> 	xorl	%eax, %eax
> 	call	printf@PLT
> 	movl	$20000, %esi
> 	leaq	.LC1(%rip), %rdi
> 	xorl	%eax, %eax
> 	call	printf@PLT
> 	subl	$1, 108(%rbx)
> 	movq	%rbp, %rdi
> 	call	pthread_mutex_unlock@PLT
> 	movq	%r12, %rax
> 	popq	%rbx
> 	.cfi_remember_state
> 	.cfi_def_cfa_offset 24
> 	popq	%rbp
> 	.cfi_def_cfa_offset 16
> 	popq	%r12
> 	.cfi_def_cfa_offset 8
> 	ret
> 	.p2align 4,,10
> 	.p2align 3

linked_list_t::del => list_t::del

[Bug c++/111026] Incorrect optimization with -o1,-o2

[zhaiqiming at baidu dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111026

--- Comment #3 from zhaiqiming at baidu dot com ---
====
[head file]


#include <stdlib.h>
#include <vector>
#include <iostream>
#include <pthread.h>

[Bug c++/111026] Incorrect optimization with -o1,-o2

[zhaiqiming at baidu dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111026

zhaiqiming at baidu dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |INVALID
             Status|WAITING                     |RESOLVED