147 lines
7.9 KiB
HTML
147 lines
7.9 KiB
HTML
<html><!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
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<html>
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<head>
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<title>80386 Programmer's Reference Manual -- Opcode RCL</title>
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</head>
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<body>
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<b>up:</b> <a href="C17.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C17.HTM">Chapter 17 -- 80386 Instruction Set</a><br>
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<b>prev:</b><a href="PUSHF.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/PUSHF.HTM"> PUSHF/PUSHFD Push Flags Register onto the Stack</a><br>
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<b>next:</b><a href="REP.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/REP.HTM"> REP/REPE/REPZ/REPNE/REPNZ Repeat Following String Operation</a>
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<p>
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<hr>
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<p>
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<h1>RCL/RCR/ROL/ROR -- Rotate</h1>
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<pre>
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Opcode Instruction Clocks Description
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D0 /2 RCL r/m8,1 9/10 Rotate 9 bits (CF,r/m byte) left
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once
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D2 /2 RCL r/m8,CL 9/10 Rotate 9 bits (CF,r/m byte) left CL
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times
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C0 /2 ib RCL r/m8,imm8 9/10 Rotate 9 bits (CF,r/m byte) left
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imm8 times
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D1 /2 RCL r/m16,1 9/10 Rotate 17 bits (CF,r/m word) left
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once
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D3 /2 RCL r/m16,CL 9/10 Rotate 17 bits (CF,r/m word) left
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CL times
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C1 /2 ib RCL r/m16,imm8 9/10 Rotate 17 bits (CF,r/m word) left
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imm8 times
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D1 /2 RCL r/m32,1 9/10 Rotate 33 bits (CF,r/m dword) left
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once
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D3 /2 RCL r/m32,CL 9/10 Rotate 33 bits (CF,r/m dword) left
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CL times
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C1 /2 ib RCL r/m32,imm8 9/10 Rotate 33 bits (CF,r/m dword) left
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imm8 times
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D0 /3 RCR r/m8,1 9/10 Rotate 9 bits (CF,r/m byte) right
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once
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D2 /3 RCR r/m8,CL 9/10 Rotate 9 bits (CF,r/m byte) right
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CL times
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C0 /3 ib RCR r/m8,imm8 9/10 Rotate 9 bits (CF,r/m byte) right
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imm8 times
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D1 /3 RCR r/m16,1 9/10 Rotate 17 bits (CF,r/m word) right
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once
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D3 /3 RCR r/m16,CL 9/10 Rotate 17 bits (CF,r/m word) right
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CL times
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C1 /3 ib RCR r/m16,imm8 9/10 Rotate 17 bits (CF,r/m word) right
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imm8 times
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D1 /3 RCR r/m32,1 9/10 Rotate 33 bits (CF,r/m dword) right
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once
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D3 /3 RCR r/m32,CL 9/10 Rotate 33 bits (CF,r/m dword) right
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CL times
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C1 /3 ib RCR r/m32,imm8 9/10 Rotate 33 bits (CF,r/m dword) right
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imm8 times
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D0 /0 ROL r/m8,1 3/7 Rotate 8 bits r/m byte left once
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D2 /0 ROL r/m8,CL 3/7 Rotate 8 bits r/m byte left CL
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times
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C0 /0 ib ROL r/m8,imm8 3/7 Rotate 8 bits r/m byte left imm8
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times
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D1 /0 ROL r/m16,1 3/7 Rotate 16 bits r/m word left once
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D3 /0 ROL r/m16,CL 3/7 Rotate 16 bits r/m word left CL
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times
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C1 /0 ib ROL r/m16,imm8 3/7 Rotate 16 bits r/m word left imm8
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times
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D1 /0 ROL r/m32,1 3/7 Rotate 32 bits r/m dword left once
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D3 /0 ROL r/m32,CL 3/7 Rotate 32 bits r/m dword left CL
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times
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C1 /0 ib ROL r/m32,imm8 3/7 Rotate 32 bits r/m dword left imm8
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times
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D0 /1 ROR r/m8,1 3/7 Rotate 8 bits r/m byte right once
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D2 /1 ROR r/m8,CL 3/7 Rotate 8 bits r/m byte right CL
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times
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C0 /1 ib ROR r/m8,imm8 3/7 Rotate 8 bits r/m word right imm8
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times
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D1 /1 ROR r/m16,1 3/7 Rotate 16 bits r/m word right once
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D3 /1 ROR r/m16,CL 3/7 Rotate 16 bits r/m word right CL
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times
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C1 /1 ib ROR r/m16,imm8 3/7 Rotate 16 bits r/m word right imm8
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times
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D1 /1 ROR r/m32,1 3/7 Rotate 32 bits r/m dword right once
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D3 /1 ROR r/m32,CL 3/7 Rotate 32 bits r/m dword right CL
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times
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C1 /1 ib ROR r/m32,imm8 3/7 Rotate 32 bits r/m dword right imm8
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times
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</pre>
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<h2>Operation</h2>
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<pre>
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(* ROL - Rotate Left *)
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temp := COUNT;
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WHILE (temp <> 0)
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DO
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tmpcf := high-order bit of (r/m);
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r/m := r/m * 2 + (tmpcf);
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temp := temp - 1;
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OD;
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IF COUNT = 1
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THEN
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IF high-order bit of r/m <> CF
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THEN OF := 1;
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ELSE OF := 0;
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FI;
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ELSE OF := undefined;
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FI;
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(* ROR - Rotate Right *)
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temp := COUNT;
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WHILE (temp <> 0 )
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DO
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tmpcf := low-order bit of (r/m);
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r/m := r/m / 2 + (tmpcf * 2^(width(r/m)));
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temp := temp - 1;
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DO;
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IF COUNT = 1
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THEN
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IF (high-order bit of r/m) <> (bit next to high-order bit of r/m)
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THEN OF := 1;
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ELSE OF := 0;
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FI;
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ELSE OF := undefined;
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FI;
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</pre>
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<h2>Description</h2>
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Each rotate instruction shifts the bits of the register or memory operand given. The left rotate instructions shift all the bits upward, except for the top bit, which is returned to the bottom. The right rotate instructions do the reverse: the bits shift downward until the bottom bit arrives at the top.
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<p>For the RCL and RCR instructions, the carry flag is part of the rotated quantity. RCL shifts the carry flag into the bottom bit and shifts the top bit into the carry flag; RCR shifts the carry flag into the top bit and shifts the bottom bit into the carry flag. For the ROL and ROR instructions, the original value of the carry flag is not a part of the result, but the carry flag receives a copy of the bit that was shifted from one end to the other.
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<p>The rotate is repeated the number of times indicated by the second operand, which is either an immediate number or the contents of the CL register. To reduce the maximum instruction execution time, the 80386 does not allow rotation counts greater than 31. If a rotation count greater than 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 does mask rotation counts.
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<p>The overflow flag is defined only for the single-rotate forms of the instructions (second operand := 1). It is undefined in all other cases. For left shifts/rotates, the CF bit after the shift is XORed with the high-order result bit. For right shifts/rotates, the high-order two bits of the result are XORed to get OF.
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<h2>Flags Affected</h2>
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OF only for single rotates; OF is undefined for multi-bit rotates; CF as described above
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<h2>Protected Mode Exceptions</h2>
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#GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal memory operand effective address in the CS, DS, ES, FS, or GS segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code) for a page fault
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<h2>Real Address Mode Exceptions</h2>
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Interrupt 13 if any part of the operand would lie outside of the effective address space from 0 to 0FFFFH
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<h2>Virtual 8086 Mode Exceptions</h2>
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Same exceptions as in Real Address Mode; #PF(fault-code) for a page fault
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<p>
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<hr>
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<p><b>up:</b> <a href="C17.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/C17.HTM">Chapter 17 -- 80386 Instruction Set</a><br>
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<b>prev:</b><a href="PUSHF.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/PUSHF.HTM"> PUSHF/PUSHFD Push Flags Register onto the Stack</a><br>
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<b>next:</b><a href="REP.HTM" tppabs="http://webster.cs.ucr.edu/Page_TechDocs/Doc386/REP.HTM"> REP/REPE/REPZ/REPNE/REPNZ Repeat Following String Operation</a>
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</body>
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