Repository: rust
Issue: Missing symbol name in optimized function
Labels: O-windows,A-debuginfo,T-compiler,C-bug,WG-debugging

I'm compiling this code on Windows with cargo build --release

```rust
use std::panic::{self, PanicInfo};
use std::process::abort;

#[inline(never)]
#[cold]
fn panic_handler(_panic_info: &PanicInfo<'_>) {
    // Put something in so this doesn't get folded
    println!("panic_handler");
    abort();
}

#[inline(never)]
fn main() {
    panic::set_hook(Box::new(panic_handler));
    panic!("Fail");
}
```

When debugging, I see the following call stack (in WinDbg):

```
0:000> k
 # Child-SP          RetAddr               Call Site
00 0000009e`ab37f400 00007ff7`d1be1069     hello!_guard_xfg_dispatch_icall_nop+0x4c
01 0000009e`ab37f460 00007ff7`d1be8f23     hello!ZN3std2rt10lang_start17h637565803574acbaE+0x59
02 (Inline Function) --------`--------     hello!alloc::boxed::impl$49::call+0xe [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\alloc\src\boxed.rs @ 2021] 
03 0000009e`ab37f490 00007ff7`d1be8d8b     hello!std::panicking::rust_panic_with_hook+0x113 [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\std\src\panicking.rs @ 786] 
04 0000009e`ab37f570 00007ff7`d1be7509     hello!std::panicking::begin_panic_handler::closure$0+0x7b [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\std\src\panicking.rs @ 649] 
05 0000009e`ab37f5e0 00007ff7`d1be8ad4     hello!std::sys_common::backtrace::__rust_end_short_backtrace<std::panicking::begin_panic_handler::closure_env$0,never$>+0x9 [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\std\src\sys_common\backtrace.rs @ 170] 
06 0000009e`ab37f610 00007ff7`d1bf9dc7     hello!std::panicking::begin_panic_handler+0x44 [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\std\src\panicking.rs @ 645] 
07 0000009e`ab37f650 00007ff7`d1be10cf     hello!core::panicking::panic_fmt+0x37 [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\core\src\panicking.rs @ 72] 
08 0000009e`ab37f6a0 00007ff7`d1be1006     hello!ZN3std2rt10lang_start17h637565803574acbaE+0xbf
09 0000009e`ab37f700 00007ff7`d1be104c     hello!__ImageBase
0a 0000009e`ab37f730 00007ff7`d1be3058     hello!ZN3std2rt10lang_start17h637565803574acbaE+0x3c
0b (Inline Function) --------`--------     hello!std::rt::lang_start_internal::closure$2+0xb [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\std\src\rt.rs @ 148] 
0c (Inline Function) --------`--------     hello!std::panicking::try::do_call+0xb [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\std\src\panicking.rs @ 552] 
0d (Inline Function) --------`--------     hello!std::panicking::try+0xb [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\std\src\panicking.rs @ 516] 
0e (Inline Function) --------`--------     hello!std::panic::catch_unwind+0xb [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\std\src\panic.rs @ 142] 
0f 0000009e`ab37f760 00007ff7`d1be1038     hello!std::rt::lang_start_internal+0xb8 [/rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library\std\src\rt.rs @ 148] 
10 0000009e`ab37f870 00007ff7`d1bf8880     hello!ZN3std2rt10lang_start17h637565803574acbaE+0x28
11 (Inline Function) --------`--------     hello!invoke_main+0x22 [D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl @ 78] 
```

Note that the top of the stack is _guard_xfg_dispatch_icall_nop. If we disassemble that function, we can see:

```
hello!_guard_xfg_dispatch_icall_nop+0xf:
00007ff7`d1bf926f cc              int     3
00007ff7`d1bf9270 4883ec58        sub     rsp,58h
00007ff7`d1bf9274 488d0525210000  lea     rax,[hello!__xt_z+0x48 (00007ff7`d1bfb3a0)]
00007ff7`d1bf927b 4889442428      mov     qword ptr [rsp+28h],rax
00007ff7`d1bf9280 48c744243001000000 mov   qword ptr [rsp+30h],1
00007ff7`d1bf9289 488d0500210000  lea     rax,[hello!__xt_z+0x38 (00007ff7`d1bfb390)]
00007ff7`d1bf9290 4889442438      mov     qword ptr [rsp+38h],rax
00007ff7`d1bf9295 0f57c0          xorps   xmm0,xmm0
00007ff7`d1bf9298 0f11442440      movups  xmmword ptr [rsp+40h],xmm0
00007ff7`d1bf929d 488d4c2428      lea     rcx,[rsp+28h]
00007ff7`d1bf92a2 e869bafeff      call    hello!std::io::stdio::_print (00007ff7`d1be4d10)
00007ff7`d1bf92a7 b907000000      mov     ecx,7
00007ff7`d1bf92ac cd29            int     29h
```

Note that the exception is at the fastfail at 00007ff7d1bf92ac (inlined from std::process::abort() ), and the function start should be at 00007ff7d1bf9270. There is however, no symbol at that address. 

```
0:000> ln 00007ff7`d1bf9270
Browse module
Set bu breakpoint

(00007ff7`d1bf9260)   hello!_guard_xfg_dispatch_icall_nop+0x10   |  (00007ff7`d1bf92b0)   hello!core::str::pattern::simd_contains::closure$2
```

There is a function entry for the code however:

```
0:000> .fnent 00007ff7`d1bf9270
Debugger function entry 00000184`6bcdb9b0 for:
(00007ff7`d1bf9260)   hello!_guard_xfg_dispatch_icall_nop+0x10   |  (00007ff7`d1bf92b0)   hello!core::str::pattern::simd_contains::closure$2

BeginAddress      = 00000000`00019270
EndAddress        = 00000000`000192b0
UnwindInfoAddress = 00000000`00020a28

Unwind info at 00007ff7`d1c00a28, 6 bytes
  version 1, flags 0, prolog 4, codes 1
  00: offs 4, unwind op 2, op info a	UWOP_ALLOC_SMALL.
```


`rustc --version --verbose`:
```
❯ rustc --version --verbose
rustc 1.75.0 (82e1608df 2023-12-21)
binary: rustc
commit-hash: 82e1608dfa6e0b5569232559e3d385fea5a93112
commit-date: 2023-12-21
host: x86_64-pc-windows-msvc
release: 1.75.0
LLVM version: 17.0.6
```