[llvm-bugs] [Bug 50839] New: [LLVM-COV] Dead code following a call site has wrong coverage.

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50839

            Bug ID: 50839
           Summary: [LLVM-COV] Dead code following a call site has wrong
                    coverage.
           Product: Runtime Libraries
           Version: 11.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: libprofile library
          Assignee: unassignedbugs at nondot.org
          Reporter: cnwy1996 at outlook.com
                CC: llvm-bugs at lists.llvm.org

$ clang -v
clang version 11.0.0
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/wangyang/llvm-project/build/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Candidate multilib: .;@m64
Selected multilib: .;@m64

$ cat test.c
#include<stdio.h>
typedef unsigned int dev_t;
typedef unsigned int kdev_t;

static inline kdev_t to_kdev_t(int dev) {
  int major, minor;

  if (sizeof(kdev_t) == 16)
    return (kdev_t)dev;
  major = (dev >> 8);
  minor = (dev & 0xff);
  return (((major) << 22) | (minor));
}

void do_mknod(const char *filename, int mode, kdev_t dev) {
  if (dev == 0x15800078)
    exit(0);
  else
    abort();
}

int sys_mknod(const char *filename, int mode, dev_t dev) {
  int error;
  char *tmp;

  tmp = (char *)((unsigned int)filename*5+1);
  error = ((long)(tmp));
  do_mknod(tmp, mode, to_kdev_t(dev));
  printf("Executed!\n");
  return error;
}

int main(void) {
  if (sizeof(int) != 4)
    exit(0);

  return sys_mknod("test", 1, 0x12345678);
}

$ clang -w -O0 -g -fcoverage-mapping -fprofile-instr-generate=test.profraw
test.c; ./a.out; llvm-profdata merge test.profraw -o test.profdata; llvm-cov
show a.out -instr-profile=test.profdata test.c > test.lcov; cat test.lcov
    1|       |#include<stdio.h>
    2|       |typedef unsigned int dev_t;
    3|       |typedef unsigned int kdev_t;
    4|       |
    5|      1|static inline kdev_t to_kdev_t(int dev) {
    6|      1|  int major, minor;
    7|      1|
    8|      1|  if (sizeof(kdev_t) == 16)
    9|      0|    return (kdev_t)dev;
   10|      1|  major = (dev >> 8);
   11|      1|  minor = (dev & 0xff);
   12|      1|  return (((major) << 22) | (minor));
   13|      1|}
   14|       |
   15|      1|void do_mknod(const char *filename, int mode, kdev_t dev) {
   16|      1|  if (dev == 0x15800078)
   17|      1|    exit(0);
   18|      0|  else
   19|      0|    abort();
   20|      1|}
   21|       |
   22|      1|int sys_mknod(const char *filename, int mode, dev_t dev) {
   23|      1|  int error;
   24|      1|  char *tmp;
   25|      1|
   26|      1|  tmp = (char *)((unsigned int)filename*5+1);
   27|      1|  error = ((long)(tmp));
   28|      1|  do_mknod(tmp, mode, to_kdev_t(dev));
   29|      1|  printf("Executed!\n");
   30|      1|  return error;
   31|      1|}
   32|       |
   33|      1|int main(void) {
   34|      1|  if (sizeof(int) != 4)
   35|      0|    exit(0);
   36|      1|
   37|      1|  return sys_mknod("test", 1, 0x12345678);
   38|      1|}

Line 29 and 30 were not executed.

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