division-vs-bitshift.cs

using System;

public class C {
    
    public static int GetUnrollCountWithDivision(ReadOnlySpan<byte> bytes)
    {
        return bytes.Length >> 7 << 3;
    }
    
    public static int GetUnrollCountWithBitshift(ReadOnlySpan<byte> bytes)
    {
        return bytes.Length / 128 * 8;
    }
}

​division-vs-bitshift.jit.asm

; Core CLR 7.0.823.31807 on x86

C..ctor()
    L0000: ret

C.GetUnrollCountWithDivision(System.ReadOnlySpan`1<Byte>)
    L0000: mov eax, [esp+8]
    L0004: sar eax, 7
    L0007: shl eax, 3
    L000a: ret 8

C.GetUnrollCountWithBitshift(System.ReadOnlySpan`1<Byte>)
    L0000: mov eax, [esp+8]
    L0004: mov edx, eax
    L0006: sar edx, 0x1f
    L0009: and edx, 0x7f
    L000c: add eax, edx
    L000e: sar eax, 7
    L0011: shl eax, 3
    L0014: ret 8

Microsoft.CodeAnalysis.EmbeddedAttribute..ctor()
    L0000: ret

System.Runtime.CompilerServices.RefSafetyRulesAttribute..ctor(Int32)
    L0000: mov [ecx+4], edx
    L0003: ret

​​.sharplab.json

{
    "version": 1,
    "target": "JIT ASM",
    "mode": "Release",
    "branch": "features-InlineArrays"
}