Oliver Horst
2013-Feb-08 15:20 UTC
[LLVMdev] Possible issue with DenseMap when using AliasSetTracker
Dear All, while willing to assist developers to adhere strictly to coding guidelines, I wrote the attached program called "alias-detector". The program's intent is to utilize the BasicAliasAnalysis to get a list of aliases for each pointer in a certain program code. First it initializes clang as frontend, executes the EmitLLVMOnlyAction, and then processes the produced Module with the following three passes: 1. BasicAliasAnalysis -- The basic alias analysis 2. AliasTrackerPass -- BasicBlockPass that creates an AliasSet for each pointer in the analyzed code (line 261 and line 94 respectively) 3. AliasDetectorPass -- BasicBlockPass that prints the AliasSet of each pointer in the analyzed code (line 264 and line 133 respectively) The first Pass seems to work flawlessly. However, the 2nd Pass fails due to a segmentation fault that somehow seems to be related to the DenseMap data structure. However, I wasn't able to pin down the issue. Accordingly, I'd like to ask for an advise. Maybe someone with more knowledge of the code basis could have a closer look on the topic and could tell whether this is really an issue of the DenseMap or me using it incorrectly. I'm currently using llvm and clang in release version 3.2. Please find attached the "alias-detector" program and its backtrace. Best regards Oliver Horst -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: alias-detector.cpp URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130208/6eefc12c/attachment.ksh> -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: backtrace.txt URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130208/6eefc12c/attachment.txt>
Nick Lewycky
2013-Feb-11 10:19 UTC
[LLVMdev] Possible issue with DenseMap when using AliasSetTracker
Oliver Horst wrote:> Dear All, > > while willing to assist developers to adhere strictly to coding guidelines, I > wrote the attached program called "alias-detector". The program's intent is to > utilize the BasicAliasAnalysis to get a list of aliases for each pointer in a > certain program code. First it initializes clang as frontend, executes the > EmitLLVMOnlyAction, and then processes the produced Module with the following > three passes: > 1. BasicAliasAnalysis -- The basic alias analysis > 2. AliasTrackerPass -- BasicBlockPass that creates an AliasSet for each pointer > in the analyzed code (line 261 and line 94 respectively) > 3. AliasDetectorPass -- BasicBlockPass that prints the AliasSet of each pointer > in the analyzed code (line 264 and line 133 respectively) > > The first Pass seems to work flawlessly. However, the 2nd Pass fails due to a > segmentation fault that somehow seems to be related to the DenseMap data > structure. However, I wasn't able to pin down the issue. Accordingly, I'd like > to ask for an advise. Maybe someone with more knowledge of the code basis could > have a closer look on the topic and could tell whether this is really an issue > of the DenseMap or me using it incorrectly. > > I'm currently using llvm and clang in release version 3.2. > Please find attached the "alias-detector" program and its backtrace.The problem is that you never added a DataLayout object to the PassManager (it's an ImmutablePass) and AliasSetTracker appears to be assuming you have one. However, I don't see such a bug with llvm on trunk, and the line numbers don't line up. Perhaps this has already been fixed? Nick
Oliver Horst
2013-Feb-11 18:02 UTC
[LLVMdev] Possible issue with DenseMap when using AliasSetTracker
Dear Nick, I followed your advise and added a DataLayout Pass, as well as updated to the trunk version of llvm and clang. However, the issue stays the same. Please find attached the updated program source and backtrace. Best Regards Oliver> -----Ursprüngliche Nachricht----- > Von: Nick Lewycky [mailto:nicholas at mxc.ca] > Gesendet: Montag, 11. Februar 2013 11:19 > An: Oliver Horst > Cc: llvmdev at cs.uiuc.edu > Betreff: Re: [LLVMdev] Possible issue with DenseMap when using > AliasSetTracker > > Oliver Horst wrote: > > Dear All, > > > > while willing to assist developers to adhere strictly to coding > > guidelines, I wrote the attached program called "alias-detector". The > > program's intent is to utilize the BasicAliasAnalysis to get a list of > > aliases for each pointer in a certain program code. First it > > initializes clang as frontend, executes the EmitLLVMOnlyAction, and > > then processes the produced Module with the following three passes: > > 1. BasicAliasAnalysis -- The basic alias analysis 2. AliasTrackerPass > > -- BasicBlockPass that creates an AliasSet for each pointer in the > > analyzed code (line 261 and line 94 respectively) 3. AliasDetectorPass > > -- BasicBlockPass that prints the AliasSet of each pointer in the > > analyzed code (line 264 and line 133 respectively) > > > > The first Pass seems to work flawlessly. However, the 2nd Pass fails > > due to a segmentation fault that somehow seems to be related to the > > DenseMap data structure. However, I wasn't able to pin down the issue. > > Accordingly, I'd like to ask for an advise. Maybe someone with more > > knowledge of the code basis could have a closer look on the topic and > > could tell whether this is really an issue of the DenseMap or me using it > incorrectly. > > > > I'm currently using llvm and clang in release version 3.2. > > Please find attached the "alias-detector" program and its backtrace. > > The problem is that you never added a DataLayout object to the PassManager > (it's an ImmutablePass) and AliasSetTracker appears to be assuming you have > one. > > However, I don't see such a bug with llvm on trunk, and the line numbers don't > line up. Perhaps this has already been fixed? > > Nick-------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: alias-detector.cpp URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130211/cf63092b/attachment.ksh> -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: backtrace.txt URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20130211/cf63092b/attachment.txt>
Reasonably Related Threads
- [LLVMdev] Possible issue with DenseMap when using AliasSetTracker
- [LLVMdev] Some questions on the output formats of AliasSetTracker
- [LLVMdev] Some questions on the output formats of AliasSetTracker
- [LLVMdev] AliasSetTracker and UnknownInst's (callsites mostly) problem
- [LLVMdev] Some questions on the output formats of AliasSetTracker