[LLVMdev] profiling basic block frequency in LLVM3.1

[patel rajendra]

Dear All LLVM Users,
 
I'm new to LLVM environment. I want to perform basic block profiling. I'm using LLVM3.1
I tried it with a simple 'c' code to find Max.No,  mentioned below.
-----------------------------------------------------------------------------------------------------------------------------------------
#include <stdio.h>
int main()
{
 unsigned int i,temp;
 
 unsigned int num[50] = {25,35,66,789,999,23,0,1,24,44,100,20,50,1,37,299,400,900,255,1000,21,26,89,877,666,432,55,58,0,90,95,111,888,94,100,32,56,78,987,90,456,1234,95,45,25,97,99,34,56,23};
  
 i = 0;
 temp = 0;
 while(i<50) {               /* FIND THE MAX NUM FROM THE ARRAY*/
       if(num[i] > temp){
           temp = num[i];
      }
      i++;
 }
 printf("Max. Num. is : %d\n", temp);
 return 0;
}
------------------------------------------------------------------------------------------------------------------------------------------------
However when I read llvmprof.out it produces following block frequencies.
 
Top 20 most frequently executed basic blocks:
 ##      %%      Frequency
  1. 27.1429%    57/210     main() - if.end
  2. 24.2857%    51/210     main() - while.cond
  3. 23.8095%    50/210     main() - while.body
  4. 20.4762%    43/210     main() - while.body.if.end_crit_edge
  5. 3.33333%     7/210     main() - if.then
  6. 0.47619%     1/210     main() - entry
  7. 0.47619%     1/210     main() - while.end
-----------------------------------------------------------------------------------------------------------------------------------------------
 
The problem is with Basic Block : if.end (first block). Why does it execute 57 times? The i++ is also part of this block. 
This shows an inconsistent profiling information.
 
Please, anyone help me to figure out where I'm doing wrong?
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Following commands are used for this profiling.
 
rdpatel55 at ubuntu:~/RDPATEL/LLVM3.1/RDSampleCode/test$ clang -O0 -emit-llvm -c -otest1.o test1.c
rdpatel55 at ubuntu:~/RDPATEL/LLVM3.1/RDSampleCode/test$ opt -disable-opt -insert-edge-profiling -o test1.o.inst test1.o
rdpatel55 at ubuntu:~/RDPATEL/LLVM3.1/RDSampleCode/test$ lli -O0 -fake-argv0 'test1.o' -load /home/rdpatel55/RDPATEL/LLVM3.1/LLVM_INSTALL_ROOT/lib/libprofile_rt.so test1.o.inst
Max. Num. is : 1234 (This is the o/p of the program)
rdpatel55 at ubuntu:~/RDPATEL/LLVM3.1/RDSampleCode/test$ llvm-prof --print-all-code test1.o.inst > bb_all.txt
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R.D.PATEL
Research Scholar,E.C.E. Department
MANIT, Bhopal
M:(91)8085090402, H:(91)8602677554
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