[Bug rtl-optimization/28657] New: could not expand __builtin_constant_p correctly

["dtemirbulatov at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

this code example could not be build for arm-elf correctly

static inline __attribute__((always_inline)) __attribute__((always_inline))
void *my_alloc(unsigned int size)
{
 if (__builtin_constant_p(size)) {
   __I_think_size_is_a_constant();
   return func2(size);
 }
 return func3(size);
}


static inline __attribute__((always_inline)) __attribute__((always_inline)) int
verify(int type, const void * addr, unsigned int size)
{
 return 0;
}

typedef struct my_struct {
 int num_entries;
 void** list;
 int list_size;
} my_struct_t;



int main_func(struct inode *inode,
        struct file *file,
        unsigned int cmd,
        unsigned long arg)
{
 struct my_struct urun;
 int res=0;
 urun.list = 0;

 switch (cmd) {
 case 1:
  func1();
  break;
 case 2:

  fill_array_randomly(&urun, sizeof(struct my_struct));



  res = (void *)
   my_alloc (urun.num_entries);

  if (urun.list) {
       int size;

       if (urun.list_size > 512) return -1;

       size = urun.list_size * sizeof(void*);

       if (verify(0, (void *)urun.list, size)) return -1;

       urun.list = (void**) my_alloc (size);

  }


 }

 return res + urun.list;
}

compiler thinks that size in my_alloc is a constant
this is a regression from 
2003-03-30  Richard Henderson   <rth@redhat.com>

        PR opt/10011, opt/10252:
         * toplev.c (rest_of_compilation): Run purge_builtin_constant_p
         before post-gcse cse pass.

and it was fixed by

2004-03-12  Roger Sayle  <roger@eyesopen.com>

       * combine.c (unmentioned_reg_p): New function to check whether an
       expression is a "specialization" of another, i.e. that there are
       no registers or memory references mentioned in the first that don't
       appear in the second.
       (unmentioned_reg_p_1): New helper subroutine of unmentioned_reg_p.
       (combine_instructions): Also try combining instructions using the
       REG_EQUAL note from a preceding log-linked instruction.


-- 
           Summary: could not expand __builtin_constant_p correctly
           Product: gcc
           Version: 3.4.6
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dtemirbulatov at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28657