Intel ITANIUM ARCHITECTURE - SOFTWARE DEVELOPERS MANUAL VOLUME 1 REV 2.3 Manual page 1538

IRET/IRETD—Interrupt Return (Continued)
IF CPL = 0
THEN
FI;
END;
RETURN-TO-OUTER-PRIVILGE-LEVEL:
IF OperandSize=32
THEN
ELSE (* OperandSize=16 *)
FI;
Read return segment selector;
IF stack segment selector is null THEN #GP(0); FI;
IF return stack segment selector index is not within its descriptor table limits
Read segment descriptor pointed to by return segment selector;
IF stack segment selector RPL  RPL of the return code segment selector
IF stack segment selector RPL  RPL of the return code segment selector
OR the stack segment descriptor does not indicate a a writable data segment;
OR stack segment DPL  RPL of the return code segment selector
FI;
IF stack segment is not present THEN #NP(SS selector); FI;
IF tempEIP is not within code segment limit THEN #GP(0); FI;
EIP  tempEIP;
CS  tempCS;
EFLAGS (CF, PF, AF, ZF, SF, TF, DF, OF, NT)  tempEFLAGS;
IF OperandSize=32
THEN
FI;
IF CPO  IOPL
THEN
FI;
IF CPL = 0
THEN
FI;
CPL  RPL of the return code segment selector;
FOR each of segment register (ES, FS, GS, and DS)
DO;
4:236
EFLAGS(IOPL)  tempEFLAGS;
IF OperandSize=32
THEN EFLAGS(VM, VIF, VIP)  tempEFLAGS;
FI;
IF top 8 bytes on stack are not within limits THEN #SS(0); FI;
IF top 4 bytes on stack are not within limits THEN #SS(0); FI;
THEN #GP(SSselector); FI;
THEN #GP(SS selector);
EFLAGS(RF, AC, ID)  tempEFLAGS;
EFLAGS(IF)  tempEFLAGS;
EFLAGS(IOPL)  tempEFLAGS;
IF OperandSize=32
THEN EFLAGS(VM, VIF, VIP)  tempEFLAGS;
FI;
IF segment register points to data or non-conforming code segment
Volume 4: Base IA-32 Instruction Reference