x86 Instruction Set Reference

TEST - Logical Compare

Opcode Mnemonic Description
A8 ib TEST AL,imm8 AND imm8 with AL; set SF, ZF, PF according to result.
A9 iw TEST AX,imm16 AND imm16 with AX; set SF, ZF, PF according to result.
A9 id TEST EAX,imm32 AND imm32 with EAX; set SF, ZF, PF according to result.
F6 /0 ib TEST r/m8,imm8 AND imm8 with r/m8; set SF, ZF, PF according to result.
F7 /0 iw TEST r/m16,imm16 AND imm16 with r/m16; set SF, ZF, PF according to result.
F7 /0 id TEST r/m32,imm32 AND imm32 with r/m32; set SF, ZF, PF according to result.
84 /r TEST r/m8,r8 AND r8 with r/m8; set SF, ZF, PF according to result.
85 /r TEST r/m16,r16 AND r16 with r/m16; set SF, ZF, PF according to result.
85 /r TEST r/m32,r32 AND r32 with r/m32; set SF, ZF, PF according to result.
Description

Computes the bit-wise logical AND of first operand (source 1 operand) and the second operand (source 2 operand) and sets the SF, ZF, and PF status flags according to the result. The result is then discarded.
Operation 
Temporary = Source1 & Source2;
SF = MSB(Temporary);
if(Temporary = 0) ZF = 1;
else ZF = 0;
PF = BitwiseXNOR(Temporary[0:7]);
for(PF = 1, i = 0; i < 8; ++i) PF ^= Temporary[i];
CF = 0;
OF = 0;
AF = Undefined;
Flags affected

The OF and CF flags are set to 0. The SF, ZF, and PF flags are set according to the result (see the "Operation" section above). The state of the AF flag is undefined.

Instruction Latency Throughput Execution Unit
CPUID0F3n/0F2n0F3n/0F2n0F2n
TEST1/0.50.5/0.5ALU