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Re: PATCH: PR target/46519: Missing vzeroupper
On Tue, Jan 4, 2011 at 3:35 PM, Mark Mitchell <mark@codesourcery.com> wrote:
> On 1/4/2011 2:09 PM, H.J. Lu wrote:
>
>> I tried to use DF. ?DF can tell me if a register is live or dead at the basic
>> block entry. ?But what I want to know is if the upper 128bit of a vector
>> register is zero, dead or live, at the basic block entry. ?Can DF tell me
>> that?
>
> DF, in the sense of math, can certainly tell you that. ?I'm not sure
> about DF, in the sense of code presently in GCC. ?But, if not, it could
> be made to do so; what you have meets the requirements for dataflow
> abstraction. ?If our infrastructure isn't powerful enough, we should
> probably make it more powerful.
>
Missing info in the current DF infrastructure:
1. Used/unused registers at basic block boundaries.
2. The accessing modes of dead/live/used/unused registers at basic
block boundaries.
3. Zero/sign extension info of live registers at the basic block entry.
--
H.J.