llvm dev - Sep 2011 - [LLVMdev] reusing FunctionPassManager with different Modules

Hi,

Is it generally safe to cache a FunctionPassManager and reuse it on modules
other than the one it was constructed with (assuming they have the same target
triple)?

paul
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On 09/23/2011 11:28 AM, Redmond, Paul wrote:
> Hi,
>
> Is it generally safe to cache a FunctionPassManager and reuse it on
> modules other than the one it was constructed with (assuming they have
> the same target triple)?
No. FunctionPass has a pair of methods, doInitialization and 
doFinalization, which take Module& and are allowed to read or modify it 
outside runOnFunction.

Nick

Thanks.

The reason I ask is because I'm looking at some code that does just that. A
single FunctionPassManager is constructed with a dummy Module and
createStandardFunctionPasses is called on it. The FunctionPassManager cached and
run on Functions in other Modules. So far I haven't noticed any problems but
I guess that is because the passes added by createStandardFunctionPasses
don't touch the Module.

paul

-----Original Message-----
From: Nick Lewycky [mailto:nicholas at mxc.ca] 
Sent: Saturday, September 24, 2011 12:21 PM
To: Redmond, Paul
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] reusing FunctionPassManager with different Modules

On 09/23/2011 11:28 AM, Redmond, Paul wrote:
> Hi,
>
> Is it generally safe to cache a FunctionPassManager and reuse it on 
> modules other than the one it was constructed with (assuming they have 
> the same target triple)?
No. FunctionPass has a pair of methods, doInitialization and doFinalization,
which take Module& and are allowed to read or modify it outside
runOnFunction.

Nick