[LLVMdev] Still Another LiveInterval Question
evan.cheng at apple.com
Thu Jan 17 15:25:01 PST 2008
On Jan 17, 2008, at 2:06 PM, David Greene wrote:
> Ok, so I'm delving much more deeply into this stuff. :)
> On a target like x86, is it true to say that for virtual registers
> phi-elimination, the only time their live intervals should have
> more than one
> value number is if they participate in 2-address instructions where
> a copy had
> to be introduced to satisfy the read-write requirements of the
> And further, in that case, LiveIntervals for virtual registers
> should only
> have at most two value numbers?
That's true only before coalescing. After coalescing, you will
frequently see intervals but more valno's.
> How about on targets without these reuiqrements? Should
> LiveIntervals for
> virtual registers only ever have one value number?
Again, true but only before coalescing.
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