[llvm-bugs] [Bug 135937] [DebugInfo] Misleading debug location at O1/2/3/g/s in inlined code

[LLVM Bugs via llvm-bugs]

Issue	135937
Summary	[DebugInfo] Misleading debug location at O1/2/3/g/s in inlined code
Labels	debuginfo
Assignees
Reporter	Apochens

    Clang version
```
Ubuntu clang version 21.0.0 (++20250415033808+d0e4af8a88dc-1~exp1~20250415153924.2354)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-21/bin
```

LLDB version
```
lldb version 21.0.0
```

Bug-triggering program
```c
 1  int printf(const char *, ...);
 2  int a, c;
 3  unsigned b = 5;
 4  int d() {
 5    if (b)
 6 return b;
 7    c = 8;  // Dead code here
 8  }
 9  int main() {
10 d();
11    printf("%X\n", a);
12  }
```

Here is the optimized LLVM IR with the misleading debug location: https://godbolt.org/z/f6e1qbdaM.
```llvm ir
define dso_local noundef i32 @main() local_unnamed_addr #1 !dbg !36 {
  ...

3: ; preds = %0
  store i32 8, ptr @c, align 4, !dbg !39, !tbaa !30 ; c = 8;
  br label %4, !dbg !40

4: ; preds = %0, %3
  ...
}

!39 = !DILocation(line: 7, column: 5, scope: !25, inlinedAt: !38)
```

When debugging, LLDB stops at the dead line:
```
Process 37755 stopped
* thread #1, name = 'origin', stop reason = step in
    frame #0: 0x0000555555555165 origin`main at origin.proc.c:7:5
   4    int d() {
   5      if (b)
   6        return b;
-> 7      c = 8;
   8    }
   9    int main() {
   10 d();
```

I suspect that this bug is caused by function inlining. cc @SLTozer @jryans 

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