foo.cs

        [MethodImpl(MethodImplOptions.NoInlining)]
        private static int SpanIndexOfInner (Span<byte> span)
        {
            byte ByteLF = (byte)'\n';
            return span.IndexOf(ByteLF);
		     }

foo.ll

define hidden monocc i32 @SpanCrash_MainClass_SpanIndexOfInner_System_Span_1_byte(%"System.Span`1<byte>"* byval %arg_span) #5 gc "mono" {
BB0:
  %0 = alloca i8, align 1
  %1 = alloca %"System.Span`1<byte>", align 8
  %2 = alloca %"System.Span`1<byte>", align 8
  %3 = alloca %"System.Span`1<byte>", align 8
  %4 = alloca %"System.Span`1<byte>", align 8
  %5 = alloca %"System.Span`1<byte>", align 8
  br label %INIT_BB1

INIT_BB1:                                         ; preds = %BB0
  %is_inited = load i8, i8* getelementptr inbounds ([3 x i8], [3 x i8]* @mono_inited, i32 0, i32 0)
  %6 = call i8 @llvm.expect.i8(i8 %is_inited, i8 1)
  %7 = icmp eq i8 %6, 0
  br i1 %7, label %NOTINITED_BB3, label %INITED_BB2

INITED_BB2:                                       ; preds = %NOTINITED_BB3, %INIT_BB1
  br label %BB3

BB3:                                              ; preds = %INITED_BB2
  br label %BB2

BB2:                                              ; preds = %BB3
  %8 = bitcast %"System.Span`1<byte>"* %arg_span to i8*
  %9 = bitcast %"System.Span`1<byte>"* %1 to i8*
  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %9, i8* %8, i32 24, i32 0, i1 false)
  store i8 10, i8* %0
  br label %BB8

BB8:                                              ; preds = %BB2
  %TYPE_FROM_HANDLE_30 = load i64*, i64** getelementptr inbounds ([0 x i64*], [0 x i64*]* bitcast (%MONO_GOT_SpanCrash.exe* @mono_aot_SpanCrash_llvm_got to [0 x i64*]*), i32 0, i32 30), !invariant.load !14
  %TYPE_FROM_HANDLE_31 = load i64*, i64** getelementptr inbounds ([0 x i64*], [0 x i64*]* bitcast (%MONO_GOT_SpanCrash.exe* @mono_aot_SpanCrash_llvm_got to [0 x i64*]*), i32 0, i32 31), !invariant.load !14
  %10 = icmp eq i64* %TYPE_FROM_HANDLE_30, %TYPE_FROM_HANDLE_31
  %t29 = zext i1 %10 to i32
  %11 = icmp eq i32 %t29, 0
  br i1 %11, label %BB10, label %BB11

BB10:                                             ; preds = %BB8
  %TYPE_FROM_HANDLE_301 = load i64*, i64** getelementptr inbounds ([0 x i64*], [0 x i64*]* bitcast (%MONO_GOT_SpanCrash.exe* @mono_aot_SpanCrash_llvm_got to [0 x i64*]*), i32 0, i32 30), !invariant.load !14
  %TYPE_FROM_HANDLE_32 = load i64*, i64** getelementptr inbounds ([0 x i64*], [0 x i64*]* bitcast (%MONO_GOT_SpanCrash.exe* @mono_aot_SpanCrash_llvm_got to [0 x i64*]*), i32 0, i32 32), !invariant.load !14
  %12 = icmp eq i64* %TYPE_FROM_HANDLE_301, %TYPE_FROM_HANDLE_32
  %t55 = zext i1 %12 to i32
  %13 = icmp eq i32 %t55, 0
  br i1 %13, label %BB12, label %BB13

BB11:                                             ; preds = %BB8
  %14 = bitcast %"System.Span`1<byte>"* %1 to i8*
  %15 = bitcast %"System.Span`1<byte>"* %3 to i8*
  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %15, i8* %14, i32 24, i32 0, i1 false)
  %16 = notail call monocc i64* @p_1_plt_System_Runtime_InteropServices_MemoryMarshal_GetReference_byte_System_Span_1_byte_llvm(%"System.Span`1<byte>"* byval %3)
  %17 = load volatile i8, i8* %0
  %18 = zext i8 %17 to i32
  %19 = bitcast %"System.Span`1<byte>"* %1 to i32*
  %20 = getelementptr i32, i32* %19, i32 4
  %t48 = load volatile i32, i32* %20
  %21 = notail call monocc i32 @p_4_plt_System_SpanHelpers_IndexOf_byte__byte_int_llvm(i64* %16, i32 %18, i32 %t48)
  br label %BB7

BB12:                                             ; preds = %BB10
  %22 = bitcast %"System.Span`1<byte>"* %1 to i8*
  %23 = bitcast %"System.Span`1<byte>"* %5 to i8*
  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %23, i8* %22, i32 24, i32 0, i1 false)
  %24 = notail call monocc i64* @p_1_plt_System_Runtime_InteropServices_MemoryMarshal_GetReference_byte_System_Span_1_byte_llvm(%"System.Span`1<byte>"* byval %5)
  %25 = load volatile i8, i8* %0
  %26 = zext i8 %25 to i32
  %27 = bitcast %"System.Span`1<byte>"* %1 to i32*
  %28 = getelementptr i32, i32* %27, i32 4
  %t88 = load volatile i32, i32* %28
  %29 = notail call monocc i32 @p_2_plt_System_SpanHelpers_IndexOf_byte_byte__byte_int_llvm(i64* %24, i32 %26, i32 %t88)
  br label %BB7

BB13:                                             ; preds = %BB10
  %30 = bitcast %"System.Span`1<byte>"* %1 to i8*
  %31 = bitcast %"System.Span`1<byte>"* %4 to i8*
  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %31, i8* %30, i32 24, i32 0, i1 false)
  %32 = notail call monocc i64* @p_1_plt_System_Runtime_InteropServices_MemoryMarshal_GetReference_byte_System_Span_1_byte_llvm(%"System.Span`1<byte>"* byval %4)
  %33 = bitcast i8* %0 to i16*
  %34 = load i16, i16* %33
  %35 = zext i16 %34 to i32
  %36 = bitcast %"System.Span`1<byte>"* %1 to i32*
  %37 = getelementptr i32, i32* %36, i32 4
  %t74 = load volatile i32, i32* %37
  %38 = notail call monocc i32 @p_3_plt_System_SpanHelpers_IndexOf_char__char_int_llvm(i64* %32, i32 %35, i32 %t74)
  br label %BB7

BB7:                                              ; preds = %BB13, %BB12, %BB11
  %39 = phi i32 [ %21, %BB11 ], [ %38, %BB13 ], [ %29, %BB12 ]
  br label %BB4

BB4:                                              ; preds = %BB7
  br label %BB1

BB1:                                              ; preds = %BB4
  ret i32 %39

NOTINITED_BB3:                                    ; preds = %INIT_BB1
  call monocc void @mono_aot_SpanCrashinit_method(i32 0)
  br label %INITED_BB2
}