Attachment #31169 for bug #58970

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      HOST_WIDE_INT adjust = bitoffset - *bitpos;

      gcc_assert ((adjust % BITS_PER_UNIT) == 0);
      if (*offset == NULL_TREE)
	*offset = size_zero_node;

      *bitpos += adjust;
      *offset

      tem = tem.sext (TYPE_PRECISION (sizetype));
      tem = tem.lshift (BITS_PER_UNIT == 8 ? 3 : exact_log2 (BITS_PER_UNIT));
      tem += bit_offset;
      if (tem.fits_shwi () && !tem.is_negative ())
	{
	  *pbitpos = tem.to_shwi ();
	  *poffset = offset = NULL_TREE;

  if (offset)
    {
      /* Avoid returning a negative bitpos as this may wreak havoc later.  */
      if (bit_offset.is_negative () || !bit_offset.fits_shwi())
        {
	  double_int mask
	    = double_int::mask (BITS_PER_UNIT == 8

Line 0 Link Here

(-)gcc/testsuite/gcc.dg/pr58970.c (+35 lines)
	1	/* PR middle-end/58970 */
	2	/* { dg-do compile } */
	3	/* { dg-options "-O2" } */
	4
	5	struct S
	6	{
	7	struct
	8	{
	9	unsigned int b:1;
	10	} t[1];
	11	};
	12
	13	void
	14	foo (int x, struct S *p)
	15	{
	16	if (x == -1)
	17	p->t[x].b = 0;
	18	}
	19
	20	struct T
	21	{
	22	char x;
	23	struct
	24	{
	25	unsigned char a : 8;
	26	unsigned char b : 1;
	27	} t[1];
	28	};
	29
	30	void
	31	bar (int x, struct T *p)
	32	{
	33	if (x == -1)
	34	p->t[x].b = 0;
	35	}

Return to bug 58970

Lines 4584-4590 get_bit_range (unsigned HOST_WIDE_INT *bitstart, Link Here

(-)gcc/expr.c (-3 / +4 lines)
4584	HOST_WIDE_INT adjust = bitoffset - *bitpos;	4584	HOST_WIDE_INT adjust = bitoffset - *bitpos;
4585		4585
4586	gcc_assert ((adjust % BITS_PER_UNIT) == 0);	4586	gcc_assert ((adjust % BITS_PER_UNIT) == 0);
4587	gcc_assert (*offset != NULL_TREE);	4587	if (*offset == NULL_TREE)
		4588	*offset = size_zero_node;
4588		4589
4589	*bitpos += adjust;	4590	*bitpos += adjust;
4590	*offset	4591	*offset
Lines 6710-6716 get_inner_reference (tree exp, HOST_WIDE_INT *pbit Link Here
6710	tem = tem.sext (TYPE_PRECISION (sizetype));	6711	tem = tem.sext (TYPE_PRECISION (sizetype));
6711	tem = tem.lshift (BITS_PER_UNIT == 8 ? 3 : exact_log2 (BITS_PER_UNIT));	6712	tem = tem.lshift (BITS_PER_UNIT == 8 ? 3 : exact_log2 (BITS_PER_UNIT));
6712	tem += bit_offset;	6713	tem += bit_offset;
6713	if (tem.fits_shwi ())	6714	if (tem.fits_shwi () && !tem.is_negative ())
6714	{	6715	{
6715	*pbitpos = tem.to_shwi ();	6716	*pbitpos = tem.to_shwi ();
6716	*poffset = offset = NULL_TREE;	6717	*poffset = offset = NULL_TREE;
Lines 6721-6727 get_inner_reference (tree exp, HOST_WIDE_INT *pbit Link Here
6721	if (offset)	6722	if (offset)
6722	{	6723	{
6723	/* Avoid returning a negative bitpos as this may wreak havoc later. */	6724	/* Avoid returning a negative bitpos as this may wreak havoc later. */
6724	if (bit_offset.is_negative ())	6725	if (bit_offset.is_negative () \|\| !bit_offset.fits_shwi())
6725	{	6726	{
6726	double_int mask	6727	double_int mask
6727	= double_int::mask (BITS_PER_UNIT == 8	6728	= double_int::mask (BITS_PER_UNIT == 8