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250 lines
14 KiB
XML
250 lines
14 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<?xml-stylesheet type="text/xsl" encoding="UTF-8" href="iform.xsl" version="1.0"?>
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<!DOCTYPE instructionsection PUBLIC "-//ARM//DTD instructionsection //EN" "iform-p.dtd">
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<!-- Copyright (c) 2010-2022 Arm Limited or its affiliates. All rights reserved. -->
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<!-- This document is Non-Confidential. This document may only be used and distributed in accordance with the terms of the agreement entered into by Arm and the party that Arm delivered this document to. -->
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<instructionsection id="BFM" title="BFM -- A64" type="instruction">
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<docvars>
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<docvar key="bitfield-fill" value="nofill" />
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<docvar key="instr-class" value="general" />
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<docvar key="isa" value="A64" />
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<docvar key="mnemonic" value="BFM" />
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</docvars>
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<heading>BFM</heading>
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<desc>
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<brief>
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<para>Bitfield Move</para>
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</brief>
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<authored>
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<para>Bitfield Move is usually accessed via one of its aliases, which are always preferred for disassembly.</para>
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<para>If <syntax><imms></syntax> is greater than or equal to <syntax><immr></syntax>, this copies a bitfield of (<syntax><imms></syntax>-<syntax><immr></syntax>+1) bits starting from bit position <syntax><immr></syntax> in the source register to the least significant bits of the destination register.</para>
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<para>If <syntax><imms></syntax> is less than <syntax><immr></syntax>, this copies a bitfield of (<syntax><imms></syntax>+1) bits from the least significant bits of the source register to bit position (regsize-<syntax><immr></syntax>) of the destination register, where regsize is the destination register size of 32 or 64 bits.</para>
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<para>In both cases the other bits of the destination register remain unchanged.</para>
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</authored>
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</desc>
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<operationalnotes>
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<para>If PSTATE.DIT is 1:</para>
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<list type="unordered">
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<listitem><content>The execution time of this instruction is independent of:<list type="unordered"><listitem><content>The values of the data supplied in any of its registers.</content></listitem><listitem><content>The values of the NZCV flags.</content></listitem></list></content></listitem>
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<listitem><content>The response of this instruction to asynchronous exceptions does not vary based on:<list type="unordered"><listitem><content>The values of the data supplied in any of its registers.</content></listitem><listitem><content>The values of the NZCV flags.</content></listitem></list></content></listitem>
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</list>
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</operationalnotes>
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<alias_list howmany="3">
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<alias_list_intro>This instruction is used by the aliases </alias_list_intro>
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<aliasref aliaspageid="BFC_BFM" aliasfile="bfc_bfm.xml" hover="Bitfield Clear" punct=", ">
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<text>BFC</text>
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<aliaspref>Rn == '11111' && <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(imms) < <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(immr)</aliaspref>
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</aliasref>
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<aliasref aliaspageid="BFI_BFM" aliasfile="bfi_bfm.xml" hover="Bitfield insert" punct=" and ">
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<text>BFI</text>
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<aliaspref>Rn != '11111' && <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(imms) < <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(immr)</aliaspref>
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</aliasref>
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<aliasref aliaspageid="BFXIL_BFM" aliasfile="bfxil_bfm.xml" hover="Bitfield extract and insert at low end" punct=".">
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<text>BFXIL</text>
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<aliaspref><a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(imms) >= <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(immr)</aliaspref>
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</aliasref>
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<alias_list_outro>
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<text> See </text>
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<aliastablelink />
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<text> below for details of when each alias is preferred.</text>
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</alias_list_outro>
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</alias_list>
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<classes>
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<iclass name="Leaving other bits unchanged" oneof="1" id="iclass_nofill" no_encodings="2" isa="A64">
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<docvars>
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<docvar key="bitfield-fill" value="nofill" />
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<docvar key="instr-class" value="general" />
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<docvar key="isa" value="A64" />
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<docvar key="mnemonic" value="BFM" />
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</docvars>
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<iclassintro count="2"></iclassintro>
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<regdiagram form="32" psname="aarch64/instrs/integer/bitfield" tworows="1">
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<box hibit="31" name="sf" usename="1">
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<c></c>
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</box>
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<box hibit="30" width="2" name="opc" usename="1" settings="2" psbits="xx">
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<c>0</c>
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<c>1</c>
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</box>
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<box hibit="28" width="6" settings="6">
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<c>1</c>
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<c>0</c>
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<c>0</c>
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<c>1</c>
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<c>1</c>
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<c>0</c>
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</box>
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<box hibit="22" name="N" usename="1">
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<c></c>
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</box>
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<box hibit="21" width="6" name="immr" usename="1">
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<c colspan="6"></c>
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</box>
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<box hibit="15" width="6" name="imms" usename="1">
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<c colspan="6"></c>
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</box>
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<box hibit="9" width="5" name="Rn" usename="1">
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<c colspan="5"></c>
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</box>
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<box hibit="4" width="5" name="Rd" usename="1">
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<c colspan="5"></c>
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</box>
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</regdiagram>
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<encoding name="BFM_32M_bitfield" oneofinclass="2" oneof="2" label="32-bit" bitdiffs="sf == 0 && N == 0">
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<docvars>
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<docvar key="bitfield-fill" value="nofill" />
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<docvar key="datatype" value="32" />
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<docvar key="instr-class" value="general" />
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<docvar key="isa" value="A64" />
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<docvar key="mnemonic" value="BFM" />
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</docvars>
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<box hibit="31" width="1" name="sf">
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<c>0</c>
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</box>
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<box hibit="22" width="1" name="N">
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<c>0</c>
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</box>
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<asmtemplate><text>BFM </text><a link="sa_wd" hover="32-bit general-purpose destination register (field "Rd")"><Wd></a><text>, </text><a link="sa_wn" hover="32-bit general-purpose source register (field "Rn")"><Wn></a><text>, #</text><a link="sa_immr" hover="Right rotate amount [0-31] (field "immr")"><immr></a><text>, #</text><a link="sa_imms" hover="Leftmost bit number to be moved from the source [0-31] (field "imms")"><imms></a></asmtemplate>
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</encoding>
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<encoding name="BFM_64M_bitfield" oneofinclass="2" oneof="2" label="64-bit" bitdiffs="sf == 1 && N == 1">
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<docvars>
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<docvar key="bitfield-fill" value="nofill" />
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<docvar key="datatype" value="64" />
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<docvar key="instr-class" value="general" />
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<docvar key="isa" value="A64" />
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<docvar key="mnemonic" value="BFM" />
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</docvars>
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<box hibit="31" width="1" name="sf">
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<c>1</c>
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</box>
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<box hibit="22" width="1" name="N">
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<c>1</c>
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</box>
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<asmtemplate><text>BFM </text><a link="sa_xd" hover="64-bit general-purpose destination register (field "Rd")"><Xd></a><text>, </text><a link="sa_xn" hover="64-bit general-purpose source register (field "Rn")"><Xn></a><text>, #</text><a link="sa_immr_1" hover="Right rotate amount [0-63] (field "immr")"><immr></a><text>, #</text><a link="sa_imms_1" hover="Leftmost bit number to be moved from the source [0-63] (field "imms")"><imms></a></asmtemplate>
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</encoding>
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<ps_section howmany="1">
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<ps name="aarch64/instrs/integer/bitfield" mylink="aarch64.instrs.integer.bitfield" enclabels="" sections="1" secttype="noheading">
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<pstext mayhavelinks="1" section="Decode" rep_section="decode">integer d = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(Rd);
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integer n = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(Rn);
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integer datasize = if sf == '1' then 64 else 32;
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boolean inzero;
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boolean extend;
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integer r;
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integer s;
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bits(datasize) wmask;
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bits(datasize) tmask;
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case opc of
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when '00' inzero = TRUE; extend = TRUE; // SBFM
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when '01' inzero = FALSE; extend = FALSE; // BFM
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when '10' inzero = TRUE; extend = FALSE; // UBFM
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when '11' UNDEFINED;
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if sf == '1' && N != '1' then UNDEFINED;
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if sf == '0' && (N != '0' || immr<5> != '0' || imms<5> != '0') then UNDEFINED;
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r = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(immr);
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s = <a link="impl-shared.UInt.1" file="shared_pseudocode.xml" hover="function: integer UInt(bits(N) x)">UInt</a>(imms);
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(wmask, tmask) = <a link="impl-aarch64.DecodeBitMasks.5" file="shared_pseudocode.xml" hover="function: (bits(M), bits(M)) DecodeBitMasks(bit immN, bits(6) imms, bits(6) immr, boolean immediate, integer M)">DecodeBitMasks</a>(N, imms, immr, FALSE, datasize);</pstext>
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</ps>
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</ps_section>
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</iclass>
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</classes>
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<explanations scope="all">
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<explanation enclist="BFM_32M_bitfield" symboldefcount="1">
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<symbol link="sa_wd"><Wd></symbol>
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<account encodedin="Rd">
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<intro>
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<para>Is the 32-bit name of the general-purpose destination register, encoded in the "Rd" field.</para>
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</intro>
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</account>
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</explanation>
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<explanation enclist="BFM_32M_bitfield" symboldefcount="1">
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<symbol link="sa_wn"><Wn></symbol>
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<account encodedin="Rn">
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<intro>
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<para>Is the 32-bit name of the general-purpose source register, encoded in the "Rn" field.</para>
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</intro>
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</account>
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</explanation>
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<explanation enclist="BFM_64M_bitfield" symboldefcount="1">
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<symbol link="sa_xd"><Xd></symbol>
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<account encodedin="Rd">
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<intro>
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<para>Is the 64-bit name of the general-purpose destination register, encoded in the "Rd" field.</para>
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</intro>
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</account>
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</explanation>
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<explanation enclist="BFM_64M_bitfield" symboldefcount="1">
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<symbol link="sa_xn"><Xn></symbol>
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<account encodedin="Rn">
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<intro>
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<para>Is the 64-bit name of the general-purpose source register, encoded in the "Rn" field.</para>
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</intro>
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</account>
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</explanation>
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<explanation enclist="BFM_32M_bitfield" symboldefcount="1">
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<symbol link="sa_immr"><immr></symbol>
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<account encodedin="immr">
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<docvars>
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<docvar key="datatype" value="32" />
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</docvars>
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<intro>
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<para>For the 32-bit variant: is the right rotate amount, in the range 0 to 31, encoded in the "immr" field.</para>
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</intro>
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</account>
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</explanation>
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<explanation enclist="BFM_64M_bitfield" symboldefcount="2">
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<symbol link="sa_immr_1"><immr></symbol>
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<account encodedin="immr">
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<docvars>
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<docvar key="datatype" value="64" />
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</docvars>
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<intro>
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<para>For the 64-bit variant: is the right rotate amount, in the range 0 to 63, encoded in the "immr" field.</para>
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</intro>
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</account>
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</explanation>
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<explanation enclist="BFM_32M_bitfield" symboldefcount="1">
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<symbol link="sa_imms"><imms></symbol>
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<account encodedin="imms">
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<docvars>
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<docvar key="datatype" value="32" />
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</docvars>
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<intro>
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<para>For the 32-bit variant: is the leftmost bit number to be moved from the source, in the range 0 to 31, encoded in the "imms" field.</para>
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</intro>
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</account>
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</explanation>
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<explanation enclist="BFM_64M_bitfield" symboldefcount="2">
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<symbol link="sa_imms_1"><imms></symbol>
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<account encodedin="imms">
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<docvars>
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<docvar key="datatype" value="64" />
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</docvars>
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<intro>
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<para>For the 64-bit variant: is the leftmost bit number to be moved from the source, in the range 0 to 63, encoded in the "imms" field.</para>
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</intro>
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</account>
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</explanation>
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</explanations>
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<aliastablehook anchor="aliasconditions">Alias Conditions</aliastablehook>
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<ps_section howmany="1">
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<ps name="aarch64/instrs/integer/bitfield" mylink="execute" enclabels="" sections="1" secttype="Operation">
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<pstext mayhavelinks="1" section="Execute" rep_section="execute">bits(datasize) dst = if inzero then <a link="impl-shared.Zeros.1" file="shared_pseudocode.xml" hover="function: bits(N) Zeros(integer N)">Zeros</a>(datasize) else <a link="impl-aarch64.X.read.2" file="shared_pseudocode.xml" hover="accessor: bits(width) X[integer n, integer width]">X</a>[d, datasize];
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bits(datasize) src = <a link="impl-aarch64.X.read.2" file="shared_pseudocode.xml" hover="accessor: bits(width) X[integer n, integer width]">X</a>[n, datasize];
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// perform bitfield move on low bits
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bits(datasize) bot = (dst AND NOT(wmask)) OR (<a link="impl-shared.ROR.2" file="shared_pseudocode.xml" hover="function: bits(N) ROR(bits(N) x, integer shift)">ROR</a>(src, r) AND wmask);
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// determine extension bits (sign, zero or dest register)
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bits(datasize) top = if extend then <a link="impl-shared.Replicate.2" file="shared_pseudocode.xml" hover="function: bits(M*N) Replicate(bits(M) x, integer N)">Replicate</a>(src<s>, datasize) else dst;
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// combine extension bits and result bits
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<a link="impl-aarch64.X.write.2" file="shared_pseudocode.xml" hover="accessor: X[integer n, integer width] = bits(width) value">X</a>[d, datasize] = (top AND NOT(tmask)) OR (bot AND tmask);</pstext>
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</ps>
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</ps_section>
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</instructionsection>
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