4.4 Integer Arithmetic Instructions

The integer arithmetic instructions perform add, subtract, multiply, signed and unsigned com- pare, and bit count operations.

Count instruction (CIX) extension implementation note:

The CIX extension to the architecture provides the CTLZ, CTPOP, and CTTZ instructions. Alpha processors for which the AMASK instruction returns bit 2 set implement these instructions. Those processors for which AMASK does not return bit 2 set can take an Illegal Instruction trap, and software can emulate their function, if required. AMASK is described in Sections 4.11.1 and D.3.

The integer instructions are summarized in Table 4–5

Table 4–5: Integer Arithmetic Instructions Summary

Mnemonic

Operation

 

 

ADD

Add Quadword/Longword

S4ADD

Scaled Add by 4

S8ADD

Scaled Add by 8

CMPEQ

Compare Signed Quadword Equal

CMPLT

Compare Signed Quadword Less Than

CMPLE

Compare Signed Quadword Less Than or Equal

CTLZ

Count leading zero

CTPOP

Count population

CTTZ

Count trailing zero

CMPULT

Compare Unsigned Quadword Less Than

CMPULE

Compare Unsigned Quadword Less Than or Equal

MUL

Multiply Quadword/Longword

UMULH

Multiply Quadword Unsigned High

SUB

Subtract Quadword/Longword

S4SUB

Scaled Subtract by 4

S8SUB

Scaled Subtract by 8

There is no integer divide instruction. Division by a constant can be done by using UMULH; division by a variable can be done by using a subroutine. See Section A.4.2.

4–24Alpha Architecture Handbook

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Compaq ECQD2KCTE manual Integer Arithmetic Instructions, Count instruction CIX extension implementation note