RS/6000 Optimizer breaks code -- suggestions?

[Wailin' Through The Nets]

This fragment of code breaks when the following function is inlined and
the code is compiled with -O on a RS/6000.  Question, why?  Note that
without -O everything works fine, even with the function inlined.
But -O kills it.

tradd(b)
union g {long xx; struct half yy;} *b;
{
	b->yy.high &= 077777;	/* WHY CAN'T I INLINE THIS? */
}

m_mult(a,b,c)
struct mint *a,*b,*c;
{
	long x;
	union {long xx; struct half yy;} sum;
	int carry;
	int i,j;
	c->val=xalloc(a->len+b->len,"m_mult");
	sum.xx=0;
	for(i=0;i<b->len;i++)
	{	carry=0;
		for(j=0;j<i+1;j++)
		{	
		sum.xx += (a->val[j])*(b->val[i-j]);
	   	if (sum.yy.high & 0100000) { 
	      		tradd(&sum); 
/*	sum.yy.high &= 077777;		*/
	      		carry += 1; 
	   	}
		c->val[i]=sum.yy.low & 077777;
		sum.xx=sum.xx >> 15;
		sum.yy.high=carry;
	etc etc etc
[Sounds to me like an optimizer bug.  Have you reported it to IBM? -John]
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