[llvm-bugs] [Bug 37084] New: [LLVM-COV] wrong coverage with incremental label pointer

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=37084

            Bug ID: 37084
           Summary: [LLVM-COV] wrong coverage with incremental label
                    pointer
           Product: Runtime Libraries
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: libprofile library
          Assignee: unassignedbugs at nondot.org
          Reporter: yangyibiao at nju.edu.cn
                CC: llvm-bugs at lists.llvm.org

$ clang -v
clang version 7.0.0- (trunk)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.4.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.2.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8.0.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.2.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8.0.0
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8.0.0
Candidate multilib: .;@m64
Selected multilib: .;@m64

$ cat small.c
int code[4]={0,0,0,1};

void bar(int *pc) {
  static const void *l[2] = {&&lab, &&end};

  goto *l[*pc];
lab:
  pc++;
  goto *l[*pc];
end:
  return;
}

int main() {
  bar(code);
  return 0;
}root at localhost:~/ccv# clang -w -O0 -g -fcoverage-mapping
-fprofile-instr-generate=small.profraw small.c; ./a.out llvm-profdata merge
small.profraw -o small.profdata; llvm-cov show a.out
-instr-profile=small.profdata small.c > small.gcov; cat small.gcov
    1|       |int code[4]={0,0,0,1};
    2|       |
    3|      1|void bar(int *pc) {
    4|      1|  static const void *l[2] = {&&lab, &&end};
    5|      1|
    6|      1|  goto *l[*pc];
    7|      3|lab:
    8|      3|  pc++;
    9|      3|  goto *l[*pc];
   10|      3|end:
   11|      1|  return;
   12|      0|}
   13|       |
   14|      1|int main() {
   15|      1|  bar(code);
   16|      1|  return 0;
   17|      1|}


***
Line #10 is wrongly marked as executed three times. 

However, the return statement only executed once. Thus, label "end" should be
only executed once.

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