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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"><HTML><HEAD><TITLE>80386 Programmer's Reference Manual -- Opcode RCL</TITLE></HEAD><BODY><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="PUSHF.htm"> PUSHF/PUSHFD Push Flags Register onto the Stack</A><BR><B>next:</B><A HREF="REP.htm"> REP/REPE/REPZ/REPNE/REPNZ Repeat Following String Operation</A><P><HR><P><H1>RCL/RCR/ROL/ROR -- Rotate</H1><PRE>Opcode Instruction Clocks DescriptionD0 /2 RCL r/m8,1 9/10 Rotate 9 bits (CF,r/m byte) left onceD2 /2 RCL r/m8,CL 9/10 Rotate 9 bits (CF,r/m byte) left CL timesC0 /2 ib RCL r/m8,imm8 9/10 Rotate 9 bits (CF,r/m byte) left imm8 timesD1 /2 RCL r/m16,1 9/10 Rotate 17 bits (CF,r/m word) left onceD3 /2 RCL r/m16,CL 9/10 Rotate 17 bits (CF,r/m word) left CL timesC1 /2 ib RCL r/m16,imm8 9/10 Rotate 17 bits (CF,r/m word) left imm8 timesD1 /2 RCL r/m32,1 9/10 Rotate 33 bits (CF,r/m dword) left onceD3 /2 RCL r/m32,CL 9/10 Rotate 33 bits (CF,r/m dword) left CL timesC1 /2 ib RCL r/m32,imm8 9/10 Rotate 33 bits (CF,r/m dword) left imm8 timesD0 /3 RCR r/m8,1 9/10 Rotate 9 bits (CF,r/m byte) right onceD2 /3 RCR r/m8,CL 9/10 Rotate 9 bits (CF,r/m byte) right CL timesC0 /3 ib RCR r/m8,imm8 9/10 Rotate 9 bits (CF,r/m byte) right imm8 timesD1 /3 RCR r/m16,1 9/10 Rotate 17 bits (CF,r/m word) right onceD3 /3 RCR r/m16,CL 9/10 Rotate 17 bits (CF,r/m word) right CL timesC1 /3 ib RCR r/m16,imm8 9/10 Rotate 17 bits (CF,r/m word) right imm8 timesD1 /3 RCR r/m32,1 9/10 Rotate 33 bits (CF,r/m dword) right onceD3 /3 RCR r/m32,CL 9/10 Rotate 33 bits (CF,r/m dword) right CL timesC1 /3 ib RCR r/m32,imm8 9/10 Rotate 33 bits (CF,r/m dword) right imm8 timesD0 /0 ROL r/m8,1 3/7 Rotate 8 bits r/m byte left onceD2 /0 ROL r/m8,CL 3/7 Rotate 8 bits r/m byte left CL timesC0 /0 ib ROL r/m8,imm8 3/7 Rotate 8 bits r/m byte left imm8 timesD1 /0 ROL r/m16,1 3/7 Rotate 16 bits r/m word left onceD3 /0 ROL r/m16,CL 3/7 Rotate 16 bits r/m word left CL timesC1 /0 ib ROL r/m16,imm8 3/7 Rotate 16 bits r/m word left imm8 timesD1 /0 ROL r/m32,1 3/7 Rotate 32 bits r/m dword left onceD3 /0 ROL r/m32,CL 3/7 Rotate 32 bits r/m dword left CL timesC1 /0 ib ROL r/m32,imm8 3/7 Rotate 32 bits r/m dword left imm8 timesD0 /1 ROR r/m8,1 3/7 Rotate 8 bits r/m byte right onceD2 /1 ROR r/m8,CL 3/7 Rotate 8 bits r/m byte right CL timesC0 /1 ib ROR r/m8,imm8 3/7 Rotate 8 bits r/m word right imm8 timesD1 /1 ROR r/m16,1 3/7 Rotate 16 bits r/m word right onceD3 /1 ROR r/m16,CL 3/7 Rotate 16 bits r/m word right CL timesC1 /1 ib ROR r/m16,imm8 3/7 Rotate 16 bits r/m word right imm8 timesD1 /1 ROR r/m32,1 3/7 Rotate 32 bits r/m dword right onceD3 /1 ROR r/m32,CL 3/7 Rotate 32 bits r/m dword right CL timesC1 /1 ib ROR r/m32,imm8 3/7 Rotate 32 bits r/m dword right imm8 times</PRE><H2>Operation</H2><PRE>(* ROL - Rotate Left *)temp := COUNT;WHILE (temp <> 0)DO tmpcf := high-order bit of (r/m); r/m := r/m * 2 + (tmpcf); temp := temp - 1;OD;IF COUNT = 1THEN IF high-order bit of r/m <> CF THEN OF := 1; ELSE OF := 0; FI;ELSE OF := undefined;FI;(* ROR - Rotate Right *)temp := COUNT;WHILE (temp <> 0 )DO tmpcf := low-order bit of (r/m); r/m := r/m / 2 + (tmpcf * 2^(width(r/m))); temp := temp - 1;DO;IF COUNT = 1THEN IF (high-order bit of r/m) <> (bit next to high-order bit of r/m) THEN OF := 1; ELSE OF := 0; FI;ELSE OF := undefined;FI;</PRE><H2>Description</H2>Each rotate instruction shifts the bits of the register or memory operandgiven. The left rotate instructions shift all the bits upward, except forthe top bit, which is returned to the bottom. The right rotate instructionsdo the reverse: the bits shift downward until the bottom bit arrives atthe top.<P>For the RCL and RCR instructions, the carry flag is part of the rotatedquantity. RCL shifts the carry flag into the bottom bit and shifts the topbit into the carry flag; RCR shifts the carry flag into the top bit andshifts the bottom bit into the carry flag. For the ROL and RORinstructions, the original value of the carry flag is not a part of theresult, but the carry flag receives a copy of the bit that was shifted fromone end to the other.<P>The rotate is repeated the number of times indicated by the secondoperand, which is either an immediate number or the contents of the CLregister. To reduce the maximum instruction execution time, the 80386does not allow rotation counts greater than 31. If a rotation count greaterthan 31 is attempted, only the bottom five bits of the rotation are used.The 8086 does not mask rotation counts. The 80386 in Virtual 8086 Mode doesmask rotation counts.<P>The overflow flag is defined only for the single-rotate forms of theinstructions (second operand := 1). It is undefined in all other cases. Forleft shifts/rotates, the CF bit after the shift is XORed with thehigh-order result bit. For right shifts/rotates, the high-order two bits ofthe result are XORed to get OF.<H2>Flags Affected</H2>OF only for single rotates; OF is undefined for multi-bit rotates; CF asdescribed above<H2>Protected Mode Exceptions</H2>#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegalmemory operand effective address in the CS, DS, ES, FS, or GSsegments; #SS(0) for an illegal address in the SS segment; #PF(fault-code)for a page fault<H2>Real Address Mode Exceptions</H2>Interrupt 13 if any part of the operand would lie outside of the effectiveaddress space from 0 to 0FFFFH<H2>Virtual 8086 Mode Exceptions</H2>Same exceptions as in Real Address Mode; #PF(fault-code) for a pagefault<P><HR><P><B>up:</B> <A HREF="c17.htm">Chapter 17 -- 80386 Instruction Set</A><BR><B>prev:</B><A HREF="PUSHF.htm"> PUSHF/PUSHFD Push Flags Register onto the Stack</A><BR><B>next:</B><A HREF="REP.htm"> REP/REPE/REPZ/REPNE/REPNZ Repeat Following String Operation</A></BODY>⌨️ 快捷键说明
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