[Bug c/89163] New: Missed optimization: sar and shr equivalent for non-negative numbers

2019-02-02 Thread tspiteri at ieee dot org 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89163

Bug ID: 89163
   Summary: Missed optimization: sar and shr equivalent for
non-negative numbers
   Product: gcc
   Version: 8.2.1
Status: UNCONFIRMED
  Keywords: missed-optimization
  Severity: normal
  Priority: P3
 Component: c
  Assignee: unassigned at gcc dot gnu.org
  Reporter: tspiteri at ieee dot org
  Target Milestone: ---

For the minimized test case below, shift is equivalent to same_as, because shr
and sar are equivalent for non-negative numbers. The generated code is not the
same.

int shift(int i) {
return i >= 0 ? (unsigned)i >> 8 : i >> 8;
}
int same_as(int i) {
return i >> 8;
}

shift:
movl%edi, %edx
movl%edi, %eax
shrl$8, %edx
sarl$8, %eax
testl   %edi, %edi
cmovns  %edx, %eax
ret

same_as:
movl%edi, %eax
sarl$8, %eax
ret

[Bug c++/47544] New: c++0x linker does not find =default constructor for explicitly instantiated template

2011-01-30 Thread tspiteri at ieee dot org 
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47544

   Summary: c++0x linker does not find =default constructor for
explicitly instantiated template
   Product: gcc
   Version: 4.5.2
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: tspit...@ieee.org


When compiling the file a.cpp below, the linker does not find the constructor
of an explicitly instantiated template if the constructor is defined using =
default.


$ cat a.cpp
template typename T
struct s {
s();
};

extern template struct sint;

template typename T
sT::s() = default;
//sT::s() {} // gives no error

template struct sint;

int main()
{
sint a;
}


$ g++-4.5 -std=c++0x a.cpp
/tmp/cc4PTe2q.o(.text+0x10): In function `main':
: undefined reference to `sint::s()'
collect2: ld returned 1 exit status


$ g++-4.5 -v
Using built-in specs.
COLLECT_GCC=g++-4.5
COLLECT_LTO_WRAPPER=/home/eeyts/root/libexec/gcc/x86_64-unknown-linux-gnu/4.5.2/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-4.5.2/configure --prefix=/home/eeyts/root
--disable-shared --enable-threads=posix --enable-__cxa_atexit --enable-libgomp
--disable-libunwind-exceptions --enable-languages=c,c++,ada
--with-gmp=/home/eeyts/root --with-mpfr=/home/eeyts/root
--with-mpc=/home/eeyts/root --with-host-libstdcxx=/usr/lib64/libstdc++.so.6
--with-ppl=/home/eeyts/root --with-cloog=/home/eeyts/root
--with-libelf=/home/eeyts/root --program-suffix=-4.5
Thread model: posix
gcc version 4.5.2 (GCC) 


$ ld -v
GNU ld version 2.15.92.0.2 20040927

[Bug c++/44870] New: -pedantic causes error when calling function with rvalue argument inside template

2010-07-08 Thread tspiteri at ieee dot org 
Inside a template function, calling another function that takes an rvalue
reference as argument with a temporary value incorrectly results in an error
when the -pedantic flag is used.


Reduced test case:

void foo(int data);

template typename T
void bar(T t)
{ foo(int()); }

void baz()
{ bar(0); }


Compilation command:

g++-4.5 -std=c++0x -c b.cpp -pedantic


Output from compilation command:

b.cpp: In function ‘void bar(T)’:
b.cpp:5:12: error: invalid initialization of reference of type ‘int’ from
expression of type ‘int’
b.cpp:1:6: error: in passing argument 1 of ‘void foo(int)’


Output of g++-4.5 -v:

Using built-in specs.
COLLECT_GCC=g++-4.5
COLLECT_LTO_WRAPPER=/home/eeyts/root/libexec/gcc/x86_64-unknown-linux-gnu/4.5.0/lto-wrapper
Target: x86_64-unknown-linux-gnu
Configured with: ../gcc-4.5.0/configure --prefix=/home/eeyts/root
--disable-shared --enable-threads=posix --enable-__cxa_atexit --enable-libgomp
--disable-libunwind-exceptions --enable-languages=c,c++
--with-gmp=/home/eeyts/root --with-mpfr=/home/eeyts/root
--with-mpc=/home/eeyts/root --with-host-libstdcxx=/usr/lib64/libstdc++.so.6
--with-ppl=/home/eeyts/root --with-cloog=/home/eeyts/root
--with-libelf=/home/eeyts/root --program-suffix=-4.5
Thread model: posix
gcc version 4.5.0 (GCC)


-- 
   Summary: -pedantic causes error when calling function with rvalue
argument inside template
   Product: gcc
   Version: 4.5.0
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: tspiteri at ieee dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44870

[Bug libstdc++/44875] New: libstdc++ status documentation fails to mention missing c++0x io members

2010-07-08 Thread tspiteri at ieee dot org 
In
http://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html#status.iso.200x,
the documentation states that 27 Input/output library is implemented, except
for 27.2.3 Thread safety, which is partially implemented. But there are missing
move constructors, move assignment operators, move() member functions, and
swap() member functions in sections 27.5 to 27.9, so I think that they should
be listed as Partial until the functions are implemented.


-- 
   Summary: libstdc++ status documentation fails to mention missing
c++0x io members
   Product: gcc
   Version: 4.6.0
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: libstdc++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: tspiteri at ieee dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44875