Incorrect debug info generation for bitfields.

[flysand7]

Context

• Odin: dev-2024-09:d2d202673
• OS: Windows 10 Unknown Edition (00000064) (version: 22H2), build 19045.4780
• CPU: 12th Gen Intel(R) Core(TM) i5-12500H
• RAM: 16088 MiB
• Backend: LLVM 18.1.8

Reproduction

1. Compile the following code with -o:none and -debug.

package bug

import "core:fmt"

main :: proc() {
    ModRM_Byte :: bit_field u8 {
        rm:  u8 | 3,
        rx:  u8 | 3,
        mod: u8 | 2,
    }
    
    b := u8(0b01010011) // mod=1, rx=2, rm=3
    modrm := (cast(^ModRM_Byte) &b)^
    fmt.printfln("%v", modrm)
    a := 3 // breakpoint here
}

2. Run the program under a debugger
3. In a debugger, put the breakpoint on the last line of the main function. In the console of the executable it should print ModRM_Byte{rm = 3, rx = 2, mod = 1}.
4. Put the variable modrm in a watch window and expand the fields. The following results will are obtained:

• RemedyBG:

• Visual Studio:

Bug

The values in the watch video do not match the printed values, which suggests incorrect generation of the debug format. Moreover it's been reported that this does not occur on other platforms, so it seems to be a windows-only bug.