llvm dev - Mar 2011 - [LLVMdev] Accessing an empty machine function before instruction selection?

I'm trying to access the MachineFunctionInfo structure from a pre-ISel pass.
In order to do this I have to get access to the MachineFunction and then call
getInfo().

Currently in my pass I request it via:
void AMDILBarrierDetect::getAnalysisUsage(AnalysisUsage &AU) const
{
  AU.addRequired<MachineFunctionAnalysis>();
  FunctionPass::getAnalysisUsage(AU);
}

However, I am getting an assert:
  assert(NormalCtor &&
           "Cannot call createPass on PassInfo without default
ctor!");

First question, is this possible? If so, how do I get NormalCtor to not be NULL?
Second question, if I want to pass information from before Instruction selection
to after instruction selection, is this the preferred way? If not how?

Thanks,
Micah
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To answer my own question.
I added this to getAnalysisUsage and it seems to bypass the assert.

AU.setPreservesAll();

Anyone have an idea on why this fixes the problem?

Thanks,
Micah

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On
Behalf Of Villmow, Micah
Sent: Friday, March 11, 2011 11:11 AM
To: llvmdev at cs.uiuc.edu
Subject: [LLVMdev] Accessing an empty machine function before instruction
selection?

I'm trying to access the MachineFunctionInfo structure from a pre-ISel pass.
In order to do this I have to get access to the MachineFunction and then call
getInfo().

Currently in my pass I request it via:
void AMDILBarrierDetect::getAnalysisUsage(AnalysisUsage &AU) const
{
  AU.addRequired<MachineFunctionAnalysis>();
  FunctionPass::getAnalysisUsage(AU);
}

However, I am getting an assert:
  assert(NormalCtor &&
           "Cannot call createPass on PassInfo without default
ctor!");

First question, is this possible? If so, how do I get NormalCtor to not be NULL?
Second question, if I want to pass information from before Instruction selection
to after instruction selection, is this the preferred way? If not how?

Thanks,
Micah
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