llvm dev - Jun 2019 - How to the get the PHI Nodes in a basic block?

Hi all,
I have an Instruction object I from where I can correctly obtain the parent
doing I.getParent(). Now I would like to understand how to obtain the PHI
Nodes in that block. Do you suggest to iterate all over the instructions
since the PHI nodes are always at the beginning or should I use another
approach? What the best way to iterate over the instructions in a block?

Thanks
Alberto
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Hi Alberto,

You’ll have to indeed iterate over the instructions, but you don’t have to go
through all of them.
You can use MachineBasicBlock::getFirstNonPHI and then iterate backward.

Cheers,
-Quentin
> On Jun 27, 2019, at 11:07 AM, Alberto Barbaro via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> 
> Hi all,
> I have an Instruction object I from where I can correctly obtain the parent
doing I.getParent(). Now I would like to understand how to obtain the PHI Nodes
in that block. Do you suggest to iterate all over the instructions since the PHI
nodes are always at the beginning or should I use another approach? What the
best way to iterate over the instructions in a block?
> 
> Thanks
> Alberto
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

BasicBlock::phis() gives you the range of PHI instructions in that block.

--
Krzysztof Parzyszek  kparzysz at quicinc.com<mailto:kparzysz at
quicinc.com>   LLVM compiler development

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Alberto
Barbaro via llvm-dev
Sent: Thursday, June 27, 2019 1:07 PM
To: llvm-dev <llvm-dev at lists.llvm.org>
Subject: [EXT] [llvm-dev] How to the get the PHI Nodes in a basic block?

Hi all,
I have an Instruction object I from where I can correctly obtain the parent
doing I.getParent(). Now I would like to understand how to obtain the PHI Nodes
in that block. Do you suggest to iterate all over the instructions since the PHI
nodes are always at the beginning or should I use another approach? What the
best way to iterate over the instructions in a block?

Thanks
Alberto
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Thanks for the answers. I'll try it tomorrow.

Alberto

On Thu, Jun 27, 2019, 21:13 Krzysztof Parzyszek <kparzysz at quicinc.com>
wrote:
> BasicBlock::phis() gives you the range of PHI instructions in that block.
>
>
>
> --
>
> Krzysztof Parzyszek  kparzysz at quicinc.com   LLVM compiler development
>
>
>
> *From:* llvm-dev <llvm-dev-bounces at lists.llvm.org> *On Behalf Of
*Alberto
> Barbaro via llvm-dev
> *Sent:* Thursday, June 27, 2019 1:07 PM
> *To:* llvm-dev <llvm-dev at lists.llvm.org>
> *Subject:* [EXT] [llvm-dev] How to the get the PHI Nodes in a basic block?
>
>
>
> Hi all,
>
> I have an Instruction object I from where I can correctly obtain the
> parent doing I.getParent(). Now I would like to understand how to obtain
> the PHI Nodes in that block. Do you suggest to iterate all over the
> instructions since the PHI nodes are always at the beginning or should I
> use another approach? What the best way to iterate over the instructions in
> a block?
>
>
>
> Thanks
>
> Alberto
>
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