llvm dev - Feb 2012 - [LLVMdev] Updating PHI for Instruction Domination?

So I have a loop with two blocks, a header (which points to return and
latch) and a latch (which points to return and header). I have inserted a
few new blocks, called H and F.

Header now points to H and latch. Latch now points to F. H points to F. F
points to Header and return.

The PHI Nodes have been updated in Header accordingly, now coming from the
preheader and F (instead of latch).

My issue is this: The values in the PHI instruction in the Header for F are
actually defined in Latch and so if you follow the path: Header->H->F,
there becomes an issue with "Instruction does not dominate all uses"
(since
the Header PHI is getting values defined in Latch coming from F but never
going to Latch) since they haven't been defined in that path.

My question is: Is there some call where I can rearrange the basic blocks
and call some functions/utils that solve this issue? Or do I have to
manually solve this myself?

Thanks again.
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By manually I meant create new value names for the F PHI in Header, and
create copy PHIs for each of those values in F that take the corresponding
value from Latch and zero (or something else) from H.


---------- Forwarded message ----------
From: Ryan Taylor <ryta1203 at gmail.com>
Date: Thu, Feb 2, 2012 at 12:08 PM
Subject: Updating PHI for Instruction Domination?
To: llvmdev at cs.uiuc.edu


So I have a loop with two blocks, a header (which points to return and
latch) and a latch (which points to return and header). I have inserted a
few new blocks, called H and F.

Header now points to H and latch. Latch now points to F. H points to F. F
points to Header and return.

The PHI Nodes have been updated in Header accordingly, now coming from the
preheader and F (instead of latch).

My issue is this: The values in the PHI instruction in the Header for F are
actually defined in Latch and so if you follow the path: Header->H->F,
there becomes an issue with "Instruction does not dominate all uses"
(since
the Header PHI is getting values defined in Latch coming from F but never
going to Latch) since they haven't been defined in that path.

My question is: Is there some call where I can rearrange the basic blocks
and call some functions/utils that solve this issue? Or do I have to
manually solve this myself?

Thanks again.
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So essentially I'm adding a path inside of the loop. Is there a way to have
llvm automatically create new IR and update the PHIs simply by adding a
block like this and changing the DomTree?

---------- Forwarded message ----------
From: Ryan Taylor <ryta1203 at gmail.com>
Date: Thu, Feb 2, 2012 at 12:08 PM
Subject: Updating PHI for Instruction Domination?
To: llvmdev at cs.uiuc.edu


So I have a loop with two blocks, a header (which points to return and
latch) and a latch (which points to return and header). I have inserted a
few new blocks, called H and F.

Header now points to H and latch. Latch now points to F. H points to F. F
points to Header and return.

The PHI Nodes have been updated in Header accordingly, now coming from the
preheader and F (instead of latch).

My issue is this: The values in the PHI instruction in the Header for F are
actually defined in Latch and so if you follow the path: Header->H->F,
there becomes an issue with "Instruction does not dominate all uses"
(since
the Header PHI is getting values defined in Latch coming from F but never
going to Latch) since they haven't been defined in that path.

My question is: Is there some call where I can rearrange the basic blocks
and call some functions/utils that solve this issue? Or do I have to
manually solve this myself?

Thanks again.
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Not that I'm aware of.

-eric

On Feb 2, 2012, at 3:47 PM, Ryan Taylor wrote:
> So essentially I'm adding a path inside of the loop. Is there a way to
have llvm automatically create new IR and update the PHIs simply by adding a
block like this and changing the DomTree?
> 
> ---------- Forwarded message ----------
> From: Ryan Taylor <ryta1203 at gmail.com>
> Date: Thu, Feb 2, 2012 at 12:08 PM
> Subject: Updating PHI for Instruction Domination?
> To: llvmdev at cs.uiuc.edu
> 
> 
> So I have a loop with two blocks, a header (which points to return and
latch) and a latch (which points to return and header). I have inserted a few
new blocks, called H and F.
> 
> Header now points to H and latch. Latch now points to F. H points to F. F
points to Header and return.
> 
> The PHI Nodes have been updated in Header accordingly, now coming from the
preheader and F (instead of latch).
> 
> My issue is this: The values in the PHI instruction in the Header for F are
actually defined in Latch and so if you follow the path: Header->H->F,
there becomes an issue with "Instruction does not dominate all uses"
(since the Header PHI is getting values defined in Latch coming from F but never
going to Latch) since they haven't been defined in that path.
> 
> My question is: Is there some call where I can rearrange the basic blocks
and call some functions/utils that solve this issue? Or do I have to manually
solve this myself?
> 
> Thanks again.
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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