image/svg+xml BLSI — Extract Lowest Set Isolated Bit Instruction Operand Encoding Description Extracts the lowest set bit from the source operand and set the corresponding bit in the destination register. All other bits in the destination operand are zeroed. If no bits are set in the source operand, BLSI sets all the bits in the destination to 0 and sets ZF and CF. This instruction is not supported in real mode and virtual-8086 mode. The operand size is always 32 bits if not in 64-bit mode. In 64-bit mode operand size 64 requires VEX.W1. VEX.W1 is ignored in non-64-bit modes. An attempt to execute this instruction with VEX.L not equal to 0 will cause #UD. Operation temp := (-SRC) bitwiseAND (SRC); SF := temp[OperandSize -1]; ZF := (temp = 0); IF SRC = 0 CF := 0; ELSE CF := 1; FI DEST := temp; Flags Affected ZF and SF are updated based on the result. CF is set if the source is not zero. OF flags are cleared. AF and PF flags are undefined. Intel C/C++ Compiler Intrinsic Equivalent BLSI:unsigned __int32 _blsi_u32(unsigned __int32 src); BLSI:unsigned __int64 _blsi_u64(unsigned __int64 src); SIMD Floating-Point Exceptions None Other Exceptions See Table2-29, “Type 13 Class Exception Conditions”. Opcode/InstructionOp/ En 64/32 -bit Mode CPUID Feature Flag Description VEX.LZ.0F38.W0 F3 /3 BLSI r32, r/m32 VMV/VBMI1Extract lowest set bit from r/m32 and set that bit in r32. VEX.LZ.0F38.W1 F3 /3 BLSI r64, r/m64 VMV/N.E.BMI1Extract lowest set bit from r/m64, and set that bit in r64. Op/EnOperand 1Operand 2Operand 3Operand 4 VMVEX.vvvv (w)ModRM:r/m (r)NANA This UNOFFICIAL reference was generated from the official Intel® 64 and IA-32 Architectures Software Developer’s Manual by a dumb script. There is no guarantee that some parts aren't mangled or broken and is distributed WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE .