Should dead stores which could trap be deleted?

[John Wehle]

Consider:

long
subr(long a, long b)
  {
  long c;

  c = a / b;

  return 0;
  }

currently gcc produces;

	pushl %ebp
	movl %esp,%ebp
	xorl %eax,%eax
	leave
	ret

when compiled -O2 on x86 due to dead_trivially_dead_insns.  Consider
the situation where b equals 0 which on the x86 normally causes a
divide by zero exception.  What are the guidelines regarding instructions
which could trap / to what extent is it valid for optimizations to modify
the behaviour of a program with respect to traps?

-- John
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