PR 17949 (unaligned memory accesses due to ivopts) question

[Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>]

Hello,

strength reduction in ivopts may turn references to "packed" fields
in structures to accesses via pointers.  The adress obtained this
way may be unaligned, which causes crash when STRICT_ALIGNMENT = 1.

This problem however does not seem to be limited to ivopts.  For example
the testcase below probably (I do not have access to the hardware
just now, so I have checked only assembler, and I cannot read ia64 asm
very well, so I am not entirely sure) fails in the same way.

It seems to me that fixing this in ivopts is not the right place.
Maybe setting DECL_NONADDRESSABLE_P for unaligned fields of structures
when STRICT_ALIGNMENT = 1 would be more correct?

Zdenek

typedef struct
{
  short i __attribute__ ((packed));
  int f[2] __attribute__ ((packed));
} A;

A a;

void foo(int *);

int main(void)
{
  foo (a.f);
  return 0;
}

void foo(int *x)
{
  *x = 0;
}