problem with analysis required

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#1

Hello,
    I was trying to get the loop info in a module pass to be able to
iterate over the loops int the module itself. Since my pass requires
to make module level changes including adding new types to module
hence a looppass cannot be used here.
I am getting the following error on running opt.

opt: /root/llvm-2.4/include/llvm/PassAnalysisSupport.h:199:
AnalysisType& llvm::Pass::getAnalysisID(const llvm::PassInfo*) const
[with AnalysisType = llvm::LoopInfo]: Assertion `ResultPass &&
"getAnalysis*() called on an analysis that was not " "'required' by
pass!"' failed.

<snip_gdb_trace>
#4 0x083006f2 in llvm::Pass::getAnalysisID<llvm::LoopInfo> (this=0x86cfc48,
    PI=0x86cbfe0) at /root/llvm-2.4/include/llvm/PassAnalysisSupport.h:197
#5 0x083007aa in llvm::Pass::getAnalysis<llvm::LoopInfo> (this=0x86cfc48)
    at /root/llvm-2.4/include/llvm/PassAnalysisSupport.h:186
#6 0x0056e1c0 in runOnModule (this=0x86cfc48, M=@0x86cfeb8) at timing.cpp:167
</snip_gdb_trace>
gdb backtrace points to the following statement in the runOnModule method;
Loopinfo * LI = &getAnalysis<LoopInfo>();

following is the content of the getAnalysis Usage method.

void getAnalysisUsage(AnalysisUsage &AU) const {
            AU.addRequired<LoopInfo> ();
            AU.addPreserved<LoopInfo> ();
}

I picked this from the LPPassManager class which has a similar
structure and its runOnFunction iterates over loop list from LoopInfo.

I think I am missing some line to add. Can someone please point out
the cause of the error??

Thanks
regards,
Kshitiz

#2

Kshitiz Garg wrote:

Hello,
    I was trying to get the loop info in a module pass to be able to
iterate over the loops int the module itself. Since my pass requires
to make module level changes including adding new types to module
hence a looppass cannot be used here.
I am getting the following error on running opt.

opt: /root/llvm-2.4/include/llvm/PassAnalysisSupport.h:199:
AnalysisType& llvm::Pass::getAnalysisID(const llvm::PassInfo*) const
[with AnalysisType = llvm::LoopInfo]: Assertion `ResultPass &&
"getAnalysis*() called on an analysis that was not " "'required' by
pass!"' failed.

<snip_gdb_trace>
#4 0x083006f2 in llvm::Pass::getAnalysisID<llvm::LoopInfo> (this=0x86cfc48,
    PI=0x86cbfe0) at /root/llvm-2.4/include/llvm/PassAnalysisSupport.h:197
#5 0x083007aa in llvm::Pass::getAnalysis<llvm::LoopInfo> (this=0x86cfc48)
    at /root/llvm-2.4/include/llvm/PassAnalysisSupport.h:186
#6 0x0056e1c0 in runOnModule (this=0x86cfc48, M=@0x86cfeb8) at timing.cpp:167
</snip_gdb_trace>
gdb backtrace points to the following statement in the runOnModule method;
Loopinfo * LI = &getAnalysis<LoopInfo>();
  

I believe the problem here is that you need to specify the function for
which you want loop information in the above call, i.e.:

Loopinfo * LI = &getAnalysis<LoopInfo>(F)

... where F is either a pointer to the Function or is a reference to the
Function (I don't recall the details off-hand; see
http://llvm.org/docs/WritingAnLLVMPass.html#getAnalysis for more
information.

You said that your pass needs to make some global modification to the
Module. In some cases, you can still write your pass as a FunctionPass;
simply put the code that changes global Module information into the
doInitialization() or doFinalization() methods.

-- John T.

#3

Hi,

Kshitiz Garg wrote:

Hello,
    I was trying to get the loop info in a module pass to be able to
iterate over the loops int the module itself. Since my pass requires
to make module level changes including adding new types to module
hence a looppass cannot be used here.
I am getting the following error on running opt.

opt: /root/llvm-2.4/include/llvm/PassAnalysisSupport.h:199:
AnalysisType& llvm::Pass::getAnalysisID(const llvm::PassInfo*) const
[with AnalysisType = llvm::LoopInfo]: Assertion `ResultPass &&
"getAnalysis*() called on an analysis that was not " "'required' by
pass!"' failed.

<snip_gdb_trace>
#4 0x083006f2 in llvm::Pass::getAnalysisID<llvm::LoopInfo> (this=0x86cfc48,
    PI=0x86cbfe0) at /root/llvm-2.4/include/llvm/PassAnalysisSupport.h:197
#5 0x083007aa in llvm::Pass::getAnalysis<llvm::LoopInfo> (this=0x86cfc48)
    at /root/llvm-2.4/include/llvm/PassAnalysisSupport.h:186
#6 0x0056e1c0 in runOnModule (this=0x86cfc48, M=@0x86cfeb8) at timing.cpp:167
</snip_gdb_trace>
gdb backtrace points to the following statement in the runOnModule method;
Loopinfo * LI = &getAnalysis<LoopInfo>();

following is the content of the getAnalysis Usage method.

void getAnalysisUsage(AnalysisUsage &AU) const {
            AU.addRequired<LoopInfo> ();
            AU.addPreserved<LoopInfo> ();
}

I picked this from the LPPassManager class which has a similar
structure and its runOnFunction iterates over loop list from LoopInfo.

I think I am missing some line to add. Can someone please point out
the cause of the error??

Funny enough I stumbled over the same problem right now. I have no solution either but I will post a follow-up if I find something out.

Andi

#4

I believe the problem here is that you need to specify the function for
which you want loop information in the above call, i.e.:

Loopinfo * LI = &getAnalysis<LoopInfo>(F)

Thanks John . Your solution worked. We need to pass the function as a
reference. However only the do initialization can do some module level
stuff but it will not serve my purpose as one is not allowed to
maintain states across 2 invocations of a function pass.

kshitiz