hw/i386.reference/RCL.htm

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   4 <TITLE>80386 Programmer's Reference Manual -- Opcode RCL</TITLE>
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   7 <B>up:</B> <A HREF="c17.htm">
   8 Chapter 17 -- 80386 Instruction Set</A><BR>
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  13 <P>
  14 <H1>RCL/RCR/ROL/ROR -- Rotate</H1>
  15
  16
  17 <PRE>
  18 Opcode       Instruction       Clocks  Description
  19
  20 D0  /2       RCL r/m8,1        9/10    Rotate 9 bits (CF,r/m byte) left
  21                                        once
  22 D2  /2       RCL r/m8,CL       9/10    Rotate 9 bits (CF,r/m byte) left CL
  23                                        times
  24 C0  /2 ib    RCL r/m8,imm8     9/10    Rotate 9 bits (CF,r/m byte) left
  25                                        imm8 times
  26 D1  /2       RCL r/m16,1       9/10    Rotate 17 bits (CF,r/m word) left
  27                                        once
  28 D3  /2       RCL r/m16,CL      9/10    Rotate 17 bits (CF,r/m word) left
  29                                        CL times
  30 C1  /2 ib    RCL r/m16,imm8    9/10    Rotate 17 bits (CF,r/m word) left
  31                                        imm8 times
  32 D1  /2       RCL r/m32,1       9/10    Rotate 33 bits (CF,r/m dword) left
  33                                        once
  34 D3  /2       RCL r/m32,CL      9/10    Rotate 33 bits (CF,r/m dword) left
  35                                        CL times
  36 C1  /2 ib    RCL r/m32,imm8    9/10    Rotate 33 bits (CF,r/m dword) left
  37                                        imm8 times
  38 D0  /3       RCR r/m8,1        9/10    Rotate 9 bits (CF,r/m byte) right
  39                                        once
  40 D2  /3       RCR r/m8,CL       9/10    Rotate 9 bits (CF,r/m byte) right
  41                                        CL times
  42 C0  /3 ib    RCR r/m8,imm8     9/10    Rotate 9 bits (CF,r/m byte) right
  43                                        imm8 times
  44 D1  /3       RCR r/m16,1       9/10    Rotate 17 bits (CF,r/m word) right
  45                                        once
  46 D3  /3       RCR r/m16,CL      9/10    Rotate 17 bits (CF,r/m word) right
  47                                        CL times
  48 C1  /3 ib    RCR r/m16,imm8    9/10    Rotate 17 bits (CF,r/m word) right
  49                                        imm8 times
  50 D1  /3       RCR r/m32,1       9/10    Rotate 33 bits (CF,r/m dword) right
  51                                        once
  52 D3  /3       RCR r/m32,CL      9/10    Rotate 33 bits (CF,r/m dword) right
  53                                        CL times
  54 C1  /3 ib    RCR r/m32,imm8    9/10    Rotate 33 bits (CF,r/m dword) right
  55                                        imm8 times
  56 D0  /0       ROL r/m8,1        3/7     Rotate 8 bits r/m byte left once
  57 D2  /0       ROL r/m8,CL       3/7     Rotate 8 bits r/m byte left CL
  58                                        times
  59 C0  /0 ib    ROL r/m8,imm8     3/7     Rotate 8 bits r/m byte left imm8
  60                                        times
  61 D1  /0       ROL r/m16,1       3/7     Rotate 16 bits r/m word left once
  62 D3  /0       ROL r/m16,CL      3/7     Rotate 16 bits r/m word left CL
  63                                        times
  64 C1  /0 ib    ROL r/m16,imm8    3/7     Rotate 16 bits r/m word left imm8
  65                                        times
  66 D1  /0       ROL r/m32,1       3/7     Rotate 32 bits r/m dword left once
  67 D3  /0       ROL r/m32,CL      3/7     Rotate 32 bits r/m dword left CL
  68                                        times
  69 C1  /0 ib    ROL r/m32,imm8    3/7     Rotate 32 bits r/m dword left imm8
  70                                        times
  71 D0  /1       ROR r/m8,1        3/7     Rotate 8 bits r/m byte right once
  72 D2  /1       ROR r/m8,CL       3/7     Rotate 8 bits r/m byte right CL
  73                                        times
  74 C0  /1 ib    ROR r/m8,imm8     3/7     Rotate 8 bits r/m word right imm8
  75                                        times
  76 D1  /1       ROR r/m16,1       3/7     Rotate 16 bits r/m word right once
  77 D3  /1       ROR r/m16,CL      3/7     Rotate 16 bits r/m word right CL
  78                                        times
  79 C1  /1 ib    ROR r/m16,imm8    3/7     Rotate 16 bits r/m word right imm8
  80                                        times
  81 D1  /1       ROR r/m32,1       3/7     Rotate 32 bits r/m dword right once
  82 D3  /1       ROR r/m32,CL      3/7     Rotate 32 bits r/m dword right CL
  83                                        times
  84 C1  /1 ib    ROR r/m32,imm8    3/7     Rotate 32 bits r/m dword right imm8
  85                                        times
  86 </PRE>
  87
  88
  89 <H2>Operation</H2>
  90
  91 <PRE>
  92 (* ROL - Rotate Left *)
  93 temp := COUNT;
  94 WHILE (temp <> 0)
  95 DO
  96    tmpcf := high-order bit of (r/m);
  97    r/m := r/m * 2 + (tmpcf);
  98    temp := temp - 1;
  99 OD;
 100 IF COUNT = 1
 101 THEN
 102    IF high-order bit of r/m <> CF
 103    THEN OF := 1;
 104    ELSE OF := 0;
 105    FI;
 106 ELSE OF := undefined;
 107 FI;
 108 (* ROR - Rotate Right *)
 109 temp := COUNT;
 110 WHILE (temp <> 0 )
 111 DO
 112    tmpcf := low-order bit of (r/m);
 113    r/m := r/m / 2 + (tmpcf * 2^(width(r/m)));
 114    temp := temp - 1;
 115 DO;
 116 IF COUNT = 1
 117 THEN
 118    IF (high-order bit of r/m) <> (bit next to high-order bit of r/m)
 119    THEN OF := 1;
 120    ELSE OF := 0;
 121    FI;
 122 ELSE OF := undefined;
 123 FI;
 124 </PRE>
 125
 126 <H2>Description</H2>
 127
 128 Each rotate instruction shifts the bits of the register or memory operand
 129 given. The left rotate instructions shift all the bits upward, except for
 130 the top bit, which is returned to the bottom. The right rotate instructions
 131 do the reverse: the bits shift downward until the bottom bit arrives at
 132 the top.
 133 <P>
 134 For the RCL and RCR instructions, the carry flag is part of the rotated
 135 quantity. RCL shifts the carry flag into the bottom bit and shifts the top
 136 bit into the carry flag; RCR shifts the carry flag into the top bit and
 137 shifts the bottom bit into the carry flag. For the ROL and ROR
 138 instructions, the original value of the carry flag is not a part of the
 139 result, but the carry flag receives a copy of the bit that was shifted from
 140 one end to the other.
 141 <P>
 142 The rotate is repeated the number of times indicated by the second
 143 operand, which is either an immediate number or the contents of the CL
 144 register. To reduce the maximum instruction execution time, the 80386
 145 does not allow rotation counts greater than 31. If a rotation count greater
 146 than 31 is attempted, only the bottom five bits of the rotation are used.
 147 The 8086 does not mask rotation counts. The 80386 in Virtual 8086 Mode does
 148 mask rotation counts.
 149 <P>
 150 The overflow flag is defined only for the single-rotate forms of the
 151 instructions (second operand := 1). It is undefined in all other cases. For
 152 left shifts/rotates, the CF bit after the shift is XORed with the
 153 high-order result bit. For right shifts/rotates, the high-order two bits of
 154 the result are XORed to get OF.
 155
 156 <H2>Flags Affected</H2>
 157
 158 OF only for single rotates; OF is undefined for multi-bit rotates; CF as
 159 described above
 160
 161 <H2>Protected Mode Exceptions</H2>
 162
 163 #GP(0) if the result is in a nonwritable segment; #GP(0) for an illegal
 164 memory operand effective address in the CS, DS, ES, FS, or GS
 165 segments; #SS(0) for an illegal address in the SS segment; #PF(fault-code)
 166 for a page fault
 167
 168 <H2>Real Address Mode Exceptions</H2>
 169
 170 Interrupt 13 if any part of the operand would lie outside of the effective
 171 address space from 0 to 0FFFFH
 172
 173 <H2>Virtual 8086 Mode Exceptions</H2>
 174
 175 Same exceptions as in Real Address Mode; #PF(fault-code) for a page
 176 fault
 177
 178
 179 <P>
 180 <HR>
 181 <P>
 182 <B>up:</B> <A HREF="c17.htm">
 183 Chapter 17 -- 80386 Instruction Set</A><BR>
 184 <B>prev:</B><A HREF="PUSHF.htm"> PUSHF/PUSHFD Push Flags Register onto the Stack</A><BR>
 185 <B>next:</B><A HREF="REP.htm"> REP/REPE/REPZ/REPNE/REPNZ Repeat Following String Operation</A>
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