Re: [Bug target/42553] New: wrong code with -O1

2009-12-30 Thread Andrew Pinski 



Sent from my iPhone

On Dec 30, 2009, at 7:56 AM, "debian-gcc at lists dot debian dot org" > wrote:


current trunk/branches on x86_64-linux-gnu. return values with  
different

compilers and different optimizations:

-O0  -O1  -O2  -O3
gcc-4.1   0222
gcc-4.3   0222
gcc-4.4   2000
gcc-4.5   0100

 Matthias

#include 
#include 

static bool atomic_test_and_reset_bit(unsigned long *v,unsigned long  
bit) {

 bool res;

 __asm__ __volatile__( "btr %2,%1\n"
   "adc $0,%0\n"
   :"=r"(res), "=m"(*v)
   :"r"(bit), "r"(0)) ;
 return res ? 1 : 0;


This inline-asm looks wrong. Because it says *v is always overriden.  
So if that function is inlined, flags down below does not have to be  
set before it.



}

int main(void)
{
 unsigned long flags = 0;
 int j;

 j = atomic_test_and_reset_bit(&flags, 2);

 printf("%d\n", j);

 return 0;
}


--
  Summary: wrong code with -O1
  Product: gcc
  Version: 4.4.3
   Status: UNCONFIRMED
 Severity: normal
 Priority: P3
Component: target
   AssignedTo: unassigned at gcc dot gnu dot org
   ReportedBy: debian-gcc at lists dot debian dot org
GCC target triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42553

[Bug target/42553] New: wrong code with -O1

2009-12-30 Thread debian-gcc at lists dot debian dot org 
current trunk/branches on x86_64-linux-gnu. return values with different
compilers and different optimizations:

 -O0  -O1  -O2  -O3
gcc-4.1   0222
gcc-4.3   0222
gcc-4.4   2000
gcc-4.5   0100

  Matthias

#include 
#include 

static bool atomic_test_and_reset_bit(unsigned long *v,unsigned long bit) {
  bool res;

  __asm__ __volatile__( "btr %2,%1\n"
"adc $0,%0\n"
:"=r"(res), "=m"(*v)
:"r"(bit), "r"(0)) ;
  return res ? 1 : 0;
}

int main(void)
{
  unsigned long flags = 0;
  int j;

  j = atomic_test_and_reset_bit(&flags, 2);

  printf("%d\n", j);

  return 0;
}


-- 
   Summary: wrong code with -O1
   Product: gcc
   Version: 4.4.3
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: debian-gcc at lists dot debian dot org
GCC target triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42553