[LLVMdev] Anomaly with CallGraph construction

[Gabriel Rodríguez]

Hi all, 

I have been trying to build a loop nesting analysis which works interprocedurally. In order 
to find the functions called inside a given loop, I am traversing the Instructions into the 
BasicBlock's that conform a Loop, and applying the code that CallGraph construction uses: 

------ extract from CallGraph.cpp : 144 
// Look for calls by this function. 
for (Function::iterator BB = F->begin(), BBE = F->end(); BB != BBE; ++BB) 
for (BasicBlock::iterator II = BB->begin(), IE = BB->end(); 
II != IE; ++II) { 
CallSite CS(cast<Value>(II)); 
if (CS && !isa<DbgInfoIntrinsic>(II)) { 
const Function *Callee = CS.getCalledFunction(); 
if (Callee) 
Node->addCalledFunction(CS, getOrInsertFunction(Callee)); 
else 
Node->addCalledFunction(CS, CallsExternalNode); 
} 
} 
------ 

While analyzing the IS NAS Parallel Benchmark I find the following BasicBlock: 

; <label>:24 ; preds = %20 
%25 = call double (...)* bitcast (double (double*, double*)* @randlc to double (...)*)(double* %t1, double* %t1) 
store double %25, double* %t2, align 8 
br label %26 

As can be seen, the first Instruction after the label contains a call to randlc(). However, this gets counted by CallGraph as an external node, since 
@randlc has been bitcasted and CS.getCalledFunction() fails to return a non-null value. As a result, the CallGraph for the caller does not contain 
randlc(), but a call to an external node instead. 


Furthermore, this behavior stems from the following definition of the function randlc() : 

----- 
double randlc( X, A ) /* Instead of randlc( double * X, double * A ) */ 
double * X; 
double * A; 
{ 
... 
} 
----- 

If defined with the types included in the header line, the generated call code does not include a bitcast of the function signature 
(although both versions of the code define randlc() using define double @randlc(double* %X, double* %A) nounwind ). 


Summarizing, I have two questions: 1) is the CallGraph analysis "working as intended" here?; and 2) what would be the correct approach 
to modifying the proposed analysis in order to detect that randlc() is being called in that CallInst ? 


Best regards, 
Gabriel 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20110329/9a303aee/attachment.html>