On Sun, Oct 14, 2012 at 11:25 PM, Eric Botcazou wrote:
>> I don't think we want to do that. A REG_EQUAL/REG_EQUIV note can use a
>> pseudo that isn't live and still be valid. Consider a simple example
>> like this:
>>
>> a = b + 3
>> // b dies here
>> c = a {REG_EQUAL b+3}
>>
>> The REG_EQUAL note is valid and may help optimization. Removing it
>> just because b is dead at that point would be unnecessarily
>> pessimistic.
>
> But if you have a REG_DEAD note for b on the first insn, then you cannot
> rematerialize the REG_EQUAL note after it, otherwise bad things can happen.
>
> See PR rtl-optimization/51505 for an example.That's not the case here. The register is only dead because the webizer renamed one of its live ranges but "forgets" to rename the EQ_NOTE use. Ciao! Steven
