Hi, How can i know, if a value have uses outside of the current basic block (liveout), without iterating through all the basic block ? Thanks. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20090530/71681bc2/attachment.html>
On Fri, May 29, 2009 at 11:37 PM, Rotem Varon<varonrotem at gmail.com> wrote:> Hi, > > How can i know, if a value have uses outside of the current basic block > (liveout), without iterating through all the basic block ? > > Thanks.Try use_iterator. See llvm/Value.h. -Eli
On May 29, 2009, at 11:37 PM, Rotem Varon wrote:> How can i know, if a value have uses outside of the current basic > block (liveout), without iterating through all the basic block ?If the value is created within the basic block in question, and the block doesn't loop to itself, then you can just iterate through the uses and note if the use is an instruction in a different block: bool isLiveOut(Instruction* I) { BasicBlock* I_BB = I->getParent(): for (Value::use_iterator ui = I->use_begin(), ue = I->use_end(); ui ! = ue; ++ui) if (cast<Instruction>(ui)->getParent() != I_BB) return true; } } If the value is created within the block but the block loops to itself, you can get away with a very slight adjustment: if (cast<Instruction>(ui)->getParent() != I_BB && !isa<PHINode>(ui)) If the value is created in one block and you want to know if it's live out of some dominated block, that's a lot more complicated (and expensive). John.
On May 29, 2009, at 11:57 PM, John McCall wrote:> If the value is created within the block but the block loops to > itself, you can get away with a very slight adjustment: > > if (cast<Instruction>(ui)->getParent() != I_BB && !isa<PHINode>(ui))Correction: this should read: if (cast<Instruction>(ui)->getParent() != I_BB || isa<PHINode>(ui)) John.
Thank you.
Is it possible to determine the liveout of the operands (see example bellow)
?
%5 = add i32 %4, %3
For '%5': i can simply use " i->isUsedOutsideOfBlock() "
For '%3' and '%4' : this is the question ...
>From your answer, is it possible to determine *which* value is liveout ( in
binary instruction)?
On Sat, May 30, 2009 at 2:57 AM, John McCall <rjmccall at apple.com>
wrote:
> On May 29, 2009, at 11:37 PM, Rotem Varon wrote:
> > How can i know, if a value have uses outside of the current basic
> > block (liveout), without iterating through all the basic block ?
>
> If the value is created within the basic block in question, and the
> block doesn't loop to itself, then you can just iterate through the
> uses and note if the use is an instruction in a different block:
>
> bool isLiveOut(Instruction* I) {
> BasicBlock* I_BB = I->getParent():
> for (Value::use_iterator ui = I->use_begin(), ue =
I->use_end(); ui
> !
> = ue; ++ui)
> if (cast<Instruction>(ui)->getParent() != I_BB)
> return true;
> }
> }
>
> If the value is created within the block but the block loops to
> itself, you can get away with a very slight adjustment:
>
> if (cast<Instruction>(ui)->getParent() != I_BB
&&
> !isa<PHINode>(ui))
>
> If the value is created in one block and you want to know if it's live
> out of some dominated block, that's a lot more complicated (and
> expensive).
>
> John.
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