[LLVMdev] Edge Profiling

C├ęsar divcesar at gmail.com
Wed Jan 30 15:23:10 PST 2013


Hello.

I'm using these commands to compile the code below in order to collect
edge/blocks profiling:

clang -emit-llvm -c sort.c -o sort.bc
opt -insert-edge-profiling sort.bc -o sort_prof.bc
clang sort_prof.bc -lprofile_rt -L/llvms/lib -o sort_prof

then I run the program and display the profiling information using
llvm-prof sort_prof.bc, and the result is:

===-------------------------------------------------------------------------===
Function execution frequencies:

 ##   Frequency
  1. 4.3e+05/708539 main
  2. 2.8e+05/708539 quickSort

  NOTE: 2 functions were never executed!
.....

My question is regarding the execution frequencies. Does make any
sense main executing 4.3e+05 times?
Why so? The code I'm compiling is below.



###################### sort.c ########################
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

const int MAX = 1000000;

void swap(int* a, int* b) {
  int tmp;
  tmp = *a;
  *a = *b;
  *b = tmp;
}

int partition(int vec[], int left, int right) {
  int i, j;

  i = left;
  for (j = left + 1; j <= right; ++j) {
    if (vec[j] < vec[left]) {
      ++i;
      swap(&vec[i], &vec[j]);
    }
  }
  swap(&vec[left], &vec[i]);

  return i;
}

void quickSort(int vec[], int left, int right) {
  int r;

  if (right > left) {
    r = partition(vec, left, right);
    quickSort(vec, left, r - 1);
    quickSort(vec, r + 1, right);
  }
}

int main(void) {

	int vet[MAX], i=0;

	srand(time(NULL));

	for (i=0; i<MAX; i++) {
		vet[i] = rand() % 654321;
	}

	quickSort(vet, 0, MAX-1);

	for (i=0; i<MAX; i++) {
		if ((rand() % 7) > 2) {
			printf("Num$[%d] = %d\n", i, vet[i]);
		}
		else if ((rand() % 4) > 2) {
			printf("Num@[%d] = %d\n", i, vet[i]);
		}
		else if ((rand() % 2) > 1) {
			printf("Num#[%d] = %d\n", i, vet[i]);
		}
	}

	return 0;
}



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