How to get source line number from .ll file LLVM

Question

I am working with LLVM 3.4 and want to obtain the line number information of source file from IR. The IR is generated from simple c code with Clang. I want to obtain the line number in source c file from the line in IR body.

I tried this -

1. For Instruction BI, unsigned Line = Line = BI->getDebugLoc().getLine();
2. For Loop L, std::cout << L->getStartLoc().getLine();

But, the result stored/printed is always 0. I don't know how to obtain line number in the source from LLVM IR.

My Source C file is -

#include <stdio.h>

int main()
{

 int i;

 int inbuf[100];
 int outbuf[100];

 for(i = 0; i < 100; ++i)        
        inbuf[i] ^= outbuf[i];

 inbuf[1] += 402;
 inbuf[6] += 107;
 inbuf[97] += 231;

 for(i = 0; i < 100; ++i)       
 {
         inbuf[i] += outbuf[i];
 }

 inbuf[47] += 312;  

    //print-statements 
 for (i=0;i<100;i++) {
        printf("inbuf[%d] = %d\n",i,inbuf[i]);              
}

return 0;

Command Used- ~/llvm/build/Release+Asserts/bin/clang -O3 -fno-unroll-loops -fno-vectorize -fno-slp-vectorize -S -emit-llvm sample.c -o sample.ll

Thanks!

Answer 1

To get line number information into .ll file your must specify both -O0 and -g flags for clang.

http://llvm.org/docs/SourceLevelDebugging.html#debugging-optimized-code

Line numbers are stored in specialized metadata nodes.

http://llvm.org/docs/LangRef.html#specialized-metadata-nodes

So the full command line must look like this:

~/llvm/build/Release+Asserts/bin/clang -O0 -g -S -emit-llvm sample.c -o sample.ll