[Bug c++/97907] New: error when compiling with optimization

[gustavo at ugr dot es via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97907

Bug ID: 97907
   Summary: error when compiling with optimization
   Product: gcc
   Version: 10.2.1
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: gustavo at ugr dot es
  Target Milestone: ---

Created attachment 49596
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=49596&action=edit
source code and makefile, also available at https://pccito.ugr.es/bug/ and
https://pccito.ugr.es/bug.tgz

3(5) should return 2 but it only works when no optimization level is applied.
f1 and f2 are two dumb functions not intended to work.

// g++ -O1 -save-temps -std=c11 -v -Wallpopcount.cc   -o popcount

#include 

unsigned f1(unsigned u)
{
unsigned c;
asm("popcnt %0, %1":"+r"(c):"r"(u));
return c;
}

unsigned f2(unsigned u)
{
unsigned c;
asm("popcnt %0, %1":"=r"(c),"=r"(u));
return c;
}

unsigned f3(unsigned u)
{
unsigned c;
asm("popcnt %1, %0":"=r"(c):"r"(u));
return c;
}

int main()
{
std::cout << "f1(5) = " << f1(5) << std::endl
  << "f2(5) = " << f2(5) << std::endl
  << "f3(5) = " << f3(5) << std::endl;
}

[Bug c++/97907] error when compiling with optimization

[gustavo at ugr dot es via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97907

--- Comment #2 from gustavo  ---
(In reply to Andreas Schwab from comment #1)
> f1 invokes undefined behaviour by modifying an input-only asm operand.

as expected... this is a test for students.

only f3 matters.

[Bug libstdc++/91488] [9/10/11/12 Regression] char_traits::length causes "inlining failed in call to always_inline" error with -fgnu-tm -O2 -std=c++17

[gustavo at ugr dot es via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91488

gustavo  changed:

   What|Removed |Added

 CC||gustavo at ugr dot es

--- Comment #5 from gustavo  ---
the bug is still here in gcc versión 11.1.1 20210531 (Red Hat 11.1.1-3) (GCC)

[Bug libstdc++/91488] [9/10/11/12 Regression] char_traits::length causes "inlining failed in call to always_inline" error with -fgnu-tm -O2 -std=c++17

[gustavo at ugr dot es via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91488

--- Comment #6 from gustavo  ---
the bug is still here in gcc versión 11.1.1 20210531 (Red Hat 11.1.1-3) (GCC)


g++ -fgnu-tm -O1 -Wallbug.cc   -o bug
In file included from /usr/include/c++/11/ios:40,
 from /usr/include/c++/11/ostream:38,
 from /usr/include/c++/11/iostream:39,
 from bug.cc:2:
/usr/include/c++/11/bits/char_traits.h: In static member function 'static
constexpr std::size_t std::char_traits::length(const char_type*)':
/usr/include/c++/11/bits/char_traits.h:257:5: error: inlining failed in call to
'always_inline' 'constexpr bool std::__constant_string_p(const _CharT*) [with
_CharT = char]': 
  257 | __constant_string_p(const _CharT* __s)
  | ^~~
/usr/include/c++/11/bits/char_traits.h:368:32: note: called from here
  368 | if (__constant_string_p(__s))
  | ~~~^
/usr/include/c++/11/bits/char_traits.h:257:5: error: inlining failed in call to
'always_inline' 'constexpr bool std::__constant_string_p(const _CharT*) [with
_CharT = char]': 
  257 | __constant_string_p(const _CharT* __s)
  | ^~~
/usr/include/c++/11/bits/char_traits.h:368:32: note: called from here
  368 | if (__constant_string_p(__s))
  | ~~~^
make: *** [: bug] Error 1

[Bug libstdc++/91488] [9/10/11/12 Regression] char_traits::length causes "inlining failed in call to always_inline" error with -fgnu-tm -O2 -std=c++17

[gustavo at ugr dot es via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91488

--- Comment #7 from gustavo  ---
can be reproduced also trunk gcc in: 
https://gcc.godbolt.org/z/v6T9j3r4M