[llvm-bugs] [Bug 51508] New: Wrong mapping assembly-line at Og

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=51508

            Bug ID: 51508
           Summary: Wrong mapping assembly-line at Og
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: DebugInfo
          Assignee: unassignedbugs at nondot.org
          Reporter: artuso at diag.uniroma1.it
                CC: jdevlieghere at apple.com, keith.walker at arm.com,
                    llvm-bugs at lists.llvm.org,
                    paul_robinson at playstation.sony.com

Comment:
The increment of variable g_64 at line 6 is assigned to wrong assembly
instructions.

Steps to reproduce bug:

root at 14f37d90482b:/home/stepping/output# clang -v
clang version 14.0.0 (https://github.com/llvm/llvm-project.git
957334382cd12ec07b46c0ddfdcc220731f6d80f)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/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

root at 14f37d90482b:/home/stepping/output# lldb -v
lldb version 14.0.0 (https://github.com/llvm/llvm-project.git revision
957334382cd12ec07b46c0ddfdcc220731f6d80f)
  clang revision 957334382cd12ec07b46c0ddfdcc220731f6d80f
  llvm revision 957334382cd12ec07b46c0ddfdcc220731f6d80f

root at 9ac1f462aecb:/home/stepping/output# cat a.c
static char b = -1;
int g_64, c;
volatile int d;
char(a)(e, f) { return e - f; }
void func_42() {
  ++g_64;
  c = 0;
  for (; c != 3; c = a(c, 1))
    d = 9 | b;
  b = 0;
}
int main() { func_42(); }

root at 9ac1f462aecb:/home/stepping/output# cat -n a.c
     1  static char b = -1;
     2  int g_64, c;
     3  volatile int d;
     4  char(a)(e, f) { return e - f; }
     5  void func_42() {
     6    ++g_64;
     7    c = 0;
     8    for (; c != 3; c = a(c, 1))
     9      d = 9 | b;
    10    b = 0;
    11  }
    12  int main() { func_42(); }

root at 9ac1f462aecb:/home/stepping/output# clang -Og -g -Wno-everything -o opt
a.c

root at 9ac1f462aecb:/home/stepping/output# lldb opt
(lldb) target create "opt"
Current executable set to '/home/stepping/output/opt' (x86_64).
(lldb) b 6
Breakpoint 1: 2 locations.
(lldb) r
Process 36 launched: '/home/stepping/output/opt' (x86_64)
Process 36 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.2
    frame #0: 0x00000000004004f0 opt`main [inlined] func_42 at a.c:6:3
   3    volatile int d;
   4    char(a)(e, f) { return e - f; }
   5    void func_42() {
-> 6      ++g_64;
   7      c = 0;
   8      for (; c != 3; c = a(c, 1))
   9        d = 9 | b;
(lldb) di -l
opt`main:
->  0x4004f0 <+0>:  addl   $0x1, 0x200b35(%rip)      ; opt.PT_LOAD[1]..bss + 3
    0x4004f7 <+7>:  cmpb   $0x0, 0x200b36(%rip)      ; c + 3
    0x4004fe <+14>: movl   $0x9, %ecx
    0x400503 <+19>: movl   $0xffffffff, %eax         ; imm = 0xFFFFFFFF
    0x400508 <+24>: cmovnel %ecx, %eax
(lldb) si
Process 36 stopped
* thread #1, name = 'opt', stop reason = instruction step into
    frame #0: 0x00000000004004f7 opt`main [inlined] func_42 at a.c:6:3
   3    volatile int d;
   4    char(a)(e, f) { return e - f; }
   5    void func_42() {
-> 6      ++g_64;
   7      c = 0;
   8      for (; c != 3; c = a(c, 1))
   9        d = 9 | b;
(lldb) di -l
opt`main:
    0x4004f0 <+0>:  addl   $0x1, 0x200b35(%rip)      ; opt.PT_LOAD[1]..bss + 3
->  0x4004f7 <+7>:  cmpb   $0x0, 0x200b36(%rip)      ; c + 3
    0x4004fe <+14>: movl   $0x9, %ecx
    0x400503 <+19>: movl   $0xffffffff, %eax         ; imm = 0xFFFFFFFF
    0x400508 <+24>: cmovnel %ecx, %eax
(lldb) si
Process 36 stopped
* thread #1, name = 'opt', stop reason = instruction step into
    frame #0: 0x00000000004004fe opt`main [inlined] func_42 at a.c:6:3
   3    volatile int d;
   4    char(a)(e, f) { return e - f; }
   5    void func_42() {
-> 6      ++g_64;
   7      c = 0;
   8      for (; c != 3; c = a(c, 1))
   9        d = 9 | b;
(lldb) di -l
opt`main:
    0x4004f0 <+0>:  addl   $0x1, 0x200b35(%rip)      ; opt.PT_LOAD[1]..bss + 3
    0x4004f7 <+7>:  cmpb   $0x0, 0x200b36(%rip)      ; c + 3
->  0x4004fe <+14>: movl   $0x9, %ecx
    0x400503 <+19>: movl   $0xffffffff, %eax         ; imm = 0xFFFFFFFF
    0x400508 <+24>: cmovnel %ecx, %eax
(lldb) si
Process 36 stopped
* thread #1, name = 'opt', stop reason = instruction step into
    frame #0: 0x0000000000400503 opt`main [inlined] func_42 at a.c:6:3
   3    volatile int d;
   4    char(a)(e, f) { return e - f; }
   5    void func_42() {
-> 6      ++g_64;
   7      c = 0;
   8      for (; c != 3; c = a(c, 1))
   9        d = 9 | b;
(lldb) di -l
opt`main:
    0x4004f0 <+0>:  addl   $0x1, 0x200b35(%rip)      ; opt.PT_LOAD[1]..bss + 3
    0x4004f7 <+7>:  cmpb   $0x0, 0x200b36(%rip)      ; c + 3
    0x4004fe <+14>: movl   $0x9, %ecx
->  0x400503 <+19>: movl   $0xffffffff, %eax         ; imm = 0xFFFFFFFF
    0x400508 <+24>: cmovnel %ecx, %eax
(lldb) si
Process 36 stopped
* thread #1, name = 'opt', stop reason = instruction step into
    frame #0: 0x0000000000400508 opt`main [inlined] func_42 at a.c:6:3
   3    volatile int d;
   4    char(a)(e, f) { return e - f; }
   5    void func_42() {
-> 6      ++g_64;
   7      c = 0;
   8      for (; c != 3; c = a(c, 1))
   9        d = 9 | b;
(lldb) di -l
opt`main:
    0x4004f0 <+0>:  addl   $0x1, 0x200b35(%rip)      ; opt.PT_LOAD[1]..bss + 3
    0x4004f7 <+7>:  cmpb   $0x0, 0x200b36(%rip)      ; c + 3
    0x4004fe <+14>: movl   $0x9, %ecx
    0x400503 <+19>: movl   $0xffffffff, %eax         ; imm = 0xFFFFFFFF
->  0x400508 <+24>: cmovnel %ecx, %eax

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