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(nonzero_bits): Handle case when BYTE_LOADS_EXTEND is not on and we

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are asked for something in a mode wider than it.

From-SVN: r5183
This commit is contained in:
Richard Kenner 1993-08-18 17:48:33 -04:00
parent 9d53c94264
commit 0840fd91a3
1 changed files with 19 additions and 0 deletions
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19
gcc/combine.c
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@ -6347,6 +6347,25 @@ nonzero_bits (x, mode)
just return the mode mask. Those tests will then be false. */
return nonzero;
#ifndef BYTE_LOADS_EXTEND
/* If X is wider than MODE, but both are a single word for both the host
and target machines, we can compute this from which bits of the
object might be nonzero in its own mode, taking into account the fact
that on many CISC machines, accessing an object in a wider mode
causes the high-order bits to become undefined. So they are
not known to be zero. */
if (GET_MODE (x) != VOIDmode && GET_MODE (x) != mode
&& GET_MODE_BITSIZE (GET_MODE (x)) <= BITS_PER_WORD
&& GET_MODE_BITSIZE (GET_MODE (x)) <= HOST_BITS_PER_WIDE_INT
&& GET_MODE_BITSIZE (mode) < GET_MODE_BITSIZE (GET_MODE (x)))
{
nonzero &= nonzero_bits (x, GET_MODE (x));
nonzero |= GET_MODE_MASK (mode) & ~ GET_MODE_MASK (GET_MODE (x));
return nonzero;
}
#endif
code = GET_CODE (x);
switch (code)
{