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87 lines
6.0 KiB
XML
87 lines
6.0 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="B_uncond" title="B -- A64" type="instruction">
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<docvars>
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<docvar key="branch-offset" value="br26" />
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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="B" />
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</docvars>
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<heading>B</heading>
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<desc>
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<brief>
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<para>Branch</para>
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</brief>
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<authored>
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<para>Branch causes an unconditional branch to a label at a PC-relative offset, with a hint that this is not a subroutine call or return.</para>
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</authored>
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</desc>
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<alias_list howmany="0"></alias_list>
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<classes>
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<iclass name="26-bit signed PC-relative branch offset" oneof="1" id="iclass_br26" no_encodings="1" isa="A64">
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<docvars>
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<docvar key="branch-offset" value="br26" />
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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="B" />
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</docvars>
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<iclassintro count="1"></iclassintro>
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<regdiagram form="32" psname="aarch64/instrs/branch/unconditional/immediate" tworows="1">
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<box hibit="31" name="op" usename="1" settings="1" psbits="x">
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<c>0</c>
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</box>
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<box hibit="30" width="5" settings="5">
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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>0</c>
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<c>1</c>
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</box>
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<box hibit="25" width="26" name="imm26" usename="1">
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<c colspan="26"></c>
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</box>
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</regdiagram>
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<encoding name="B_only_branch_imm" oneofinclass="1" oneof="1" label="">
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<docvars>
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<docvar key="branch-offset" value="br26" />
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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="B" />
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</docvars>
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<asmtemplate><text>B </text><a link="sa_label" hover="Label to be unconditionally branched to (field imm26)"><label></a></asmtemplate>
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</encoding>
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<ps_section howmany="1">
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<ps name="aarch64/instrs/branch/unconditional/immediate" mylink="aarch64.instrs.branch.unconditional.immediate" enclabels="" sections="1" secttype="noheading">
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<pstext mayhavelinks="1" section="Decode" rep_section="decode"><a link="BranchType" file="shared_pseudocode.xml" hover="enumeration BranchType { BranchType_DIRCALL, BranchType_INDCALL, BranchType_ERET, BranchType_DBGEXIT, BranchType_RET, BranchType_DIR, BranchType_INDIR, BranchType_EXCEPTION, BranchType_TMFAIL, BranchType_RESET, BranchType_UNKNOWN}">BranchType</a> branch_type = if op == '1' then <a link="BranchType_DIRCALL" file="shared_pseudocode.xml" hover="enumeration BranchType { BranchType_DIRCALL, BranchType_INDCALL, BranchType_ERET, BranchType_DBGEXIT, BranchType_RET, BranchType_DIR, BranchType_INDIR, BranchType_EXCEPTION, BranchType_TMFAIL, BranchType_RESET, BranchType_UNKNOWN}">BranchType_DIRCALL</a> else <a link="BranchType_DIR" file="shared_pseudocode.xml" hover="enumeration BranchType { BranchType_DIRCALL, BranchType_INDCALL, BranchType_ERET, BranchType_DBGEXIT, BranchType_RET, BranchType_DIR, BranchType_INDIR, BranchType_EXCEPTION, BranchType_TMFAIL, BranchType_RESET, BranchType_UNKNOWN}">BranchType_DIR</a>;
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bits(64) offset = <a link="impl-shared.SignExtend.2" file="shared_pseudocode.xml" hover="function: bits(N) SignExtend(bits(M) x, integer N)">SignExtend</a>(imm26:'00', 64);</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="B_only_branch_imm" symboldefcount="1">
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<symbol link="sa_label"><label></symbol>
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<account encodedin="imm26">
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<intro>
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<para>Is the program label to be unconditionally branched to. Its offset from the address of this instruction, in the range +/-128MB, is encoded as "imm26" times 4.</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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<ps_section howmany="1">
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<ps name="aarch64/instrs/branch/unconditional/immediate" mylink="execute" enclabels="" sections="1" secttype="Operation">
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<pstext mayhavelinks="1" section="Execute" rep_section="execute">if branch_type == <a link="BranchType_DIRCALL" file="shared_pseudocode.xml" hover="enumeration BranchType { BranchType_DIRCALL, BranchType_INDCALL, BranchType_ERET, BranchType_DBGEXIT, BranchType_RET, BranchType_DIR, BranchType_INDIR, BranchType_EXCEPTION, BranchType_TMFAIL, BranchType_RESET, BranchType_UNKNOWN}">BranchType_DIRCALL</a> then
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if <a link="impl-shared.HaveGCS.0" file="shared_pseudocode.xml" hover="function: boolean HaveGCS()">HaveGCS</a>() && <a link="impl-aarch64.GCSPCREnabled.1" file="shared_pseudocode.xml" hover="function: boolean GCSPCREnabled(bits(2) el)">GCSPCREnabled</a>(PSTATE.EL) then
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<a link="impl-aarch64.AddGCSRecord.1" file="shared_pseudocode.xml" hover="function: AddGCSRecord(bits(64) vaddress)">AddGCSRecord</a>(<a link="impl-aarch64.PC.read.0" file="shared_pseudocode.xml" hover="accessor: bits(64) PC[]">PC</a>[] + 4);
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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>[30, 64] = <a link="impl-aarch64.PC.read.0" file="shared_pseudocode.xml" hover="accessor: bits(64) PC[]">PC</a>[] + 4;
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boolean branch_conditional = FALSE;
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<a link="impl-shared.BranchTo.3" file="shared_pseudocode.xml" hover="function: BranchTo(bits(N) target, BranchType branch_type, boolean branch_conditional)">BranchTo</a>(<a link="impl-aarch64.PC.read.0" file="shared_pseudocode.xml" hover="accessor: bits(64) PC[]">PC</a>[] + offset, branch_type, branch_conditional);</pstext>
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</ps>
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</ps_section>
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</instructionsection>
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