Intel 64 and IA-32 Architectures Software Developers Manual Volume 2A, Instruction Set Reference, A-M

Vol. 2 3-255
INSTRUCTION SET REFERENCE, A-M
Operation
IF OperandSize = 16 (* CWD instruction *)
THEN
DX ← SignExtend(AX);
ELSE IF OperandSize
= 32 (* CDQ instruction *)
EDX ← SignExtend(EAX); FI;
ELSE IF 64-Bit Mode and OperandSize = 64 (* CQO instruction*)
RDX ← SignExtend(RAX); FI;
FI;
Flags Affected
None.
Exceptions (All Operating Modes)
None.