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Return from subroutine branches unconditionally to an address in a register, with a hint that this is a subroutine return.
31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
1 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | Rn | 0 | 0 | 0 | 0 | 0 | ||||
Z | op | A | M | Rm |
RET {<Xn>}
integer n = UInt(Rn);
BranchType branch_type;
integer m = UInt(Rm);
boolean pac = (A == '1');
boolean use_key_a = (M == '0');
boolean source_is_sp = ((Z == '1') && (m == 31));
if !pac && m != 0 then
UNDEFINED;
elsif pac && !if !pac && m != 0 thenUnallocatedEncoding();
elsif pac && !HavePACExt() then
UNDEFINED;
case op of
when '00' branch_type =() then BranchType_INDIRUnallocatedEncoding;
when '01' branch_type =();
case op of
when '00' branch_type = BranchType_INDCALLBranchType_JMP;
when '10' branch_type = when '01' branch_type = BranchType_CALL;
when '10' branch_type = BranchType_RET;
otherwise UNDEFINED;
if pac then
if Z == '0' && m != 31 then
UNDEFINED;
if branch_type == otherwise UnallocatedEncoding();
if pac then
if Z == '0' && m != 31 then
UnallocatedEncoding();
if branch_type == BranchType_RET then
if n !=31 then UnallocatedEncoding then
if n != 31 then UNDEFINED;
();
n = 30;
source_is_sp = TRUE;
<Xn> | Is the 64-bit name of the general-purpose register holding the address to be branched to, encoded in the "Rn" field. Defaults to X30 if absent. |
bits(64) target = X[n];
case branch_type of
whenif pac then
bits(64) modifier = if source_is_sp then BranchType_INDIR
if InGuardedPage then
if n == 16 || n == 17 then
BTypeNext = '01';
else
BTypeNext = '11';
else
BTypeNext = '01';
when BranchType_INDCALL
BTypeNext = '10';
when BranchType_RET
BTypeNext = '00';
if pac then
bits(64) modifier = if source_is_sp then SP[] else X[m];
if use_key_a then
target = AuthIA(target, modifier);
else
target = AuthIB(target, modifier);
if branch_type == BranchType_INDCALLBranchType_CALL then X[30] = PC[] + 4;
BranchTo(target, branch_type);
If PSTATE.DIT is 1:
Internal version only: isa v30.25v29.05, AdvSIMD v27.01v26.0, pseudocode v85-xml-00bet8_rc3v35.3
; Build timestamp: 2018-09-13T132018-06-16T09:0445
Copyright © 2010-2018 ARM Limited or its affiliates. All rights reserved. This document is Non-Confidential.
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