Non-optimized inlining regression

[kerams]

Since #19548 inline functions are not inlined in debug builds, including those where inlining is not negotiable.

Repro steps

open System
open FSharp.NativeInterop
#nowarn 9

// without inlining the returned Span points at a stack position that is no longer valid
let inline stackalloc<'a when 'a: unmanaged> length =
    Span<'a> (NativePtr.stackalloc<'a> length |> NativePtr.toVoidPtr, length)

let rec clobber n =
    let mutable a = int64 n
    let mutable b = a * 2L
    let mutable c = b * 2L
    let mutable d = c * 2L
    if n > 0 then clobber (n - 1) + int (a + b + c + d) else 0

let demo () =
    let b = stackalloc<char> 3
    b.[0] <- 'a'
    b.[1] <- 'b'
    b.[2] <- 'c'
    clobber 64 |> ignore
    String b

let r = demo ()
printfn "expected: \"abc\" [97; 98; 99]"
printfn "actual:   %A %A" r (r |> Seq.map int |> Seq.toList)

Expected behavior

> dotnet fsi .\stackalloc-inline-repro.fsx
expected: "abc" [97; 98; 99]
actual:   "abc" [97; 98; 99]
> dotnet fsi --optimize- .\stackalloc-inline-repro.fsx
expected: "abc" [97; 98; 99]
actual:   "abc" [97; 98; 99]

Actual behavior

> dotnet fsi .\stackalloc-inline-repro.fsx
expected: "abc" [97; 98; 99]
actual:   "abc" [97; 98; 99]
> dotnet fsi --optimize- .\stackalloc-inline-repro.fsx
expected: "abc" [97; 98; 99]
actual:   "?" [63; 0; 0]

Known workarounds

Optimize debug builds.

Related information

SDK 11.0.100-preview.6.26359.118