[PATCH] D18831: [Coverage] Use the count value of the outer region for an expansion region.

[Igor Kudrin via llvm-commits]

ikudrin added a comment.

The motivation case for this patch is the following:

  $ cat > sample.cpp << EOF
  #define DO_LOOP1() \
      for (int K = 0; K < 2; ++K) {}
  
  #define DO_LOOP2() \
      for (int K = 0; K < 2; ++K) {}
  
  #define JUST_EXPAND() DO_LOOP2()
  
  int main() {
      DO_LOOP1();
      JUST_EXPAND();
      return 0;
  }
  EOF
  $ clang++ -fprofile-instr-generate -fcoverage-mapping sample.cpp 
  $ ./a.out
  $ llvm-profdata merge -o default.profdata default.profraw
  $ llvm-cov show a.out -instr-profile default.profdata
         |    1|#define DO_LOOP1() \
        3|    2|    for (int K = 0; K < 2; ++K) {}
         |    3|
         |    4|#define DO_LOOP2() \
        3|    5|    for (int K = 0; K < 2; ++K) {}
         |    6|
        3|    7|#define JUST_EXPAND() DO_LOOP2()
         |    8|
        1|    9|int main() {
        3|   10|    DO_LOOP1();
        1|   11|    JUST_EXPAND();
        1|   12|    return 0;
        1|   13|}

As you may see, the counts for `DO_LOOP` macroses are 3, and these values are propagated to the outer code. As a result, counts for lines 7 and 10 are shown as `3` which looks quite weird.
After applying the patch, the output of llvm-cov looks more predictable:

  $ llvm-cov show a.out -instr-profile default.profdata
         |    1|#define DO_LOOP1() \
        3|    2|    for (int K = 0; K < 2; ++K) {}
         |    3|
         |    4|#define DO_LOOP2() \
        3|    5|    for (int K = 0; K < 2; ++K) {}
         |    6|
        1|    7|#define JUST_EXPAND() DO_LOOP2()
         |    8|
        1|    9|int main() {
        1|   10|    DO_LOOP1();
        1|   11|    JUST_EXPAND();
        1|   12|    return 0;
        1|   13|}


http://reviews.llvm.org/D18831