pdep

Parallel Bits Deposit

PDEP r32, r32, r/m32

Scatters bits from LSB of source to positions marked in mask.

Pseudocode Operation

result ← 0; src_bit ← 0; for (i = 0; i < operand_size; i++) { if (src2[i]) { result[i] ← src1[src_bit]; src_bit += 1; } } dest ← result;

Example

PDEP eax, eax, ebx

Encoding

Binary Layout

VEX

opcode

ModRM

Format VEX

Opcode VEX.LZ.F2.0F38.W0 F5 /r

Extension BMI2

Operands

dest
32-bit general-purpose register (e.g. EAX)
src1
32-bit general-purpose register (e.g. EAX)
src2
32-bit register or memory

Reference

View in Intel® 64 and IA-32 Architectures SDM ↗ Intel® SDM

Instruction Forms

Opcode	Instruction	Op/En	64/32-bit Mode	CPUID	Description
VEX.LZ.F2.0F38.W0 F5 /r	PDEP r32a, r32b, r/m32	RVM	V/V	BMI2	Parallel deposit of bits from r32b using mask in r/m32, result is written to r32a.
VEX.LZ.F2.0F38.W1 F5 /r	PDEP r64a, r64b, r/m64	RVM	V/N.E.	BMI2	Parallel deposit of bits from r64b using mask in r/m64, result is written to r64a.

Description

PDEP uses a mask in the second source operand (the third operand) to transfer/scatter contiguous low order bits in the first source operand (the second operand) into the destination (the first operand). PDEP takes the low bits from the first source operand and deposit them in the destination operand at the corresponding bit locations that are set in the second source operand (mask). All other bits (bits not set in mask) in destination are set to zero.

SRC1 S31 S30 S29 S28 S27 S7 S6 S5 S4 S3 S2 S1 S0

SRC2 0 0 0 1 0 1 0 1 0 0 1 0 0 (mask)

DEST 0 0 0 S3 0 S2 0 S1 0 0 S0 0 0 bit 31 bit 0

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 := SRC1;
MASK := SRC2;
DEST := 0 ;
m := 0, k := 0;
DO WHILE m < OperandSize

IF MASK[ m] = 1 THEN
DEST[ m] := TEMP[ k];
k := k+ 1;
FI
m := m+ 1;
OD

Intel C/C++ Compiler Intrinsic Equivalent

PDEP unsigned __int32 _pdep_u32(unsigned __int32 src, unsigned __int32 mask);
PDEP unsigned __int64 _pdep_u64(unsigned __int64 src, unsigned __int32 mask);

Flags Affected

None.

Exceptions

SIMD Floating-Point Exceptions