Intel 253666-024US - Manual (Page 185)

Vol. 2A 3-139
INSTRUCTION SET REFERENCE, A-M
CMPS/CMPSB/CMPSW/CMPSD/CMPSQ—Compare String Operands
(R|E)DI ← (R|E)DI – 2;
FI;
ELSE IF (Doubleword comparison)
THEN IF DF = 0
THEN
(R|E)SI ← (R|E)SI + 4;
(R|E)DI ← (R|E)DI + 4;
ELSE
(R|E)SI ← (R|E)SI – 4;
(R|E)DI ← (R|E)DI – 4;
FI;
ELSE (* Quadword comparison *)
THEN IF DF
=
0
(R|E)SI ← (R|E)SI + 8;
(R|E)DI ← (R|E)DI + 8;
ELSE
(R|E)SI ← (R|E)SI – 8;
(R|E)DI ← (R|E)DI – 8;
FI;
FI;
ELSE (* Non-64-bit Mode *)
IF (byte comparison)
THEN IF DF
=
0
THEN
(E)SI ← (E)SI + 1;
(E)DI ← (E)DI + 1;
ELSE
(E)SI ← (E)SI – 1;
(E)DI ← (E)DI – 1;
FI;
ELSE IF (Word comparison)
THEN IF DF
=
0
(E)SI ← (E)SI + 2;
(E)DI ← (E)DI + 2;
ELSE
(E)SI ← (E)SI – 2;
(E)DI ← (E)DI – 2;
FI;
ELSE (* Doubleword comparison *)
THEN IF DF
=
0
(E)SI ← (E)SI + 4;
(E)DI ← (E)DI + 4;
ELSE