bsf

[brandonros]

{
    "i": 2993,
    "iHex": "bb1",
    "x64dbgLine": {
      "rawLine": {
        "Index": "00BB1",
        "Address": "000000014501BC20",
        "Bytes": "45:0FBCDF",
        "Disassembly": "bsf r11d,r15d",
        "Registers": "",
        "Memory": "",
        "Comments": ""
      },
      "rip": "14501bc20",
      "registerChanges": [],
      "memoryChanges": []
    },
    "scemuLine": {
      "rawLine": {
        "diffRegLine": "diff_reg: pos = 2993 rip = 14501bc20 r11 9d46c36de8c10d85 -> e8c10d85;",
        "memTraceLines": [
          {
            "rawLine": "mem_trace: pos = 2993 rip = 14501bc1d op = write bits = 32 address = 0x14f288 value = 0xe8c199fa name = 'stack'",
            "position": "bb1",
            "rip": "14501bc1d",
            "operation": "write",
            "bits": "20",
            "address": "14f288",
            "value": "e8c199fa"
          }
        ]
      },
      "position": "bb1",
      "rip": "14501bc20",
      "registerChanges": [
        {
          "registerName": "r11",
          "previousValue": "9d46c36de8c10d85",
          "newValue": "e8c10d85"
        }
      ],
      "memoryChanges": [
        {
          "address": "14f288",
          "previousValue": 0,
          "newValue": "e8c199fa"
        }
      ]
    },
    "instructionErrors": [
      {
        "index": 0,
        "message": "unmatchedRegisterChange mismatch (scemu but not x64dbg)",
        "scemu": "r11"
      }
    ]
  },

[brandonros]

should be a no-op?

[brandonros]

2994 0x14501bc20: bsf   r11d,r15d
/!\ undefined behavior on BSF with src == 0
	diff_flags: pos = 2993 rip = 14501bc20 in = 296 out = 2d6 f_zf 0 -> 1; 
	diff_reg: pos = 2993 rip = 14501bc20 r11 9d46c36de8c10d85 -> e8c10d85; 
	rax: 0xfffffffffff63e25 rbx: 0x5370 rcx: 0x144fa54ec rdx: 0x144fa54ec rsi: 0x14f490 rdi: 0x144e4713b rbp: 0x144ec1d56 rsp: 0x14f288
	r8: 0x50 r9: 0x14f480 r10: 0x8cb75dbe12d3c81d r11: 0xe8c10d85 r12: 0x1448a76a4 r13: 0x0 r14: 0x140000000 r15: 0x0
	r8u: 0x0 r9u: 0x0 r10u: 0x8cb75dbe r11u: 0x0 r12u: 0x1 r13u: 0x0 r14u: 0x1 r15u: 0x0
	r8d: 0x50 r9d: 0x14f480 r10d: 0x12d3c81d r11d: 0xe8c10d85 r12d: 0x448a76a4 r13d: 0x0 r14d: 0x40000000 r15d: 0x0
	r8w: 0x50 r9w: 0xf480 r10w: 0xc81d r11w: 0xd85 r12w: 0x76a4 r13w: 0x0 r14w: 0x0 r15w: 0x0
	r8l: 0x50 r9l: 0x80 r10l: 0x1d r11l: 0x85 r12l: 0xa4 r13l: 0x0 r14l: 0x0 r15l: 0x0
	zf: true pf: true af: true of: false sf: true df: false cf: false tf: false if: true nt: false

[sha0coder]

it's a nop but enabling ZF, like the manual says:
https://www.felixcloutier.com/x86/bsf

is it incorrect enabling ZF?

[sha0coder]

I did a test on x64dbg and it's enabling the ZF.

[brandonros]

"x64dbgLine": {
      "rawLine": {
        "Index": "00BB1",
        "Address": "000000014501BC20",
        "Bytes": "45:0FBCDF",
        "Disassembly": "bsf r11d,r15d",
        "Registers": "",
        "Memory": "",
        "Comments": ""
      },
      "rip": "14501bc20",
      "registerChanges": [],
      "memoryChanges": []
    },

this means in x64dbg it is not modifying and registers or any memory writes

[brandonros]

"registerChanges": [
        {
          "registerName": "r11",
          "previousValue": "9d46c36de8c10d85",
          "newValue": "e8c10d85"
        }
      ],

in scemu we should not have this change, this is what i mean by "should be no-op"?

[sha0coder]

fixed.