PATCH: PR rtl-optimization/50696: [x32] Unnecessary lea
Thu Oct 13 21:51:00 GMT 2011
On Thu, Oct 13, 2011 at 2:23 PM, Richard Kenner
>> Does it look OK?
> If I understand your code correctly, there's essentially the same code
> as you have a bit above that:
> /* If the constant is one less than a power of two, this might be
> representable by an extraction even if no shift is present.
> If it doesn't end up being a ZERO_EXTEND, we will ignore it unless
> we are in a COMPARE. */
> else if ((i = exact_log2 (INTVAL (XEXP (x, 1)) + 1)) >= 0)
> new_rtx = make_extraction (mode,
> make_compound_operation (XEXP (x, 0),
> 0, NULL_RTX, i, 1, 0, in_code == COMPARE);
> So you need to understand why your code "fires" and it doesn't.
It is because mask 0xffffffff is optimized to 0xfffffffc by keeping track
of non-zero bits in registers and the above code doesn't take that
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