[llvm-bugs] [Bug 35577] New: [Clang-optimization] wrong code on incremental operator in a loop

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=35577

            Bug ID: 35577
           Summary: [Clang-optimization] wrong code on incremental
                    operator in a loop
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: yangyibiao at nju.edu.cn
                CC: llvm-bugs at lists.llvm.org

$ clang -v
clang version 6.0.0-svn319838-1~exp1 (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/7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.2.0
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
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.2.0
Candidate multilib: .;@m64
Selected multilib: .;@m64

$ cat small.c
int printf(const char *, ...);
union {
  short a;
  long b;
} c;
short *d = &c.a;
int e = 0;
long *f = &c.b;
int main() {
  for (; e <= 1; e++) {
    *f = 0;
    ++*d;
  }
  printf("%d\n", c.a);
}

$ clang -O0 small.c; ./a.out
1
$ clang -Ofast small.c; ./a.out
2

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20171208/eee1adb7/attachment-0001.html>