BTI

Branch Target Identification. A BTI instruction is used to guard against the execution of instructions which are not the intended target of a branch.

Outside of a guarded memory region, a BTI instruction executes as a NOP. Within a guarded memory region while PSTATE.BTYPE != 0b00, a BTI instruction compatible with the current value of PSTATE.BTYPE will not generate a Branch Target Exception and will allow execution of subsequent instructions within the memory region.

The operand <targets> passed to a BTI instruction determines the values of PSTATE.BTYPE which the BTI instruction is compatible with.

Within a guarded memory region, when PSTATE.BTYPE != 0b00, all instructions will generate a Branch Target Exception, other than BRK, BTI, HLT, PACIASP, and PACIBSP, which might not. See the individual instructions for more information.

System
(FEAT_BTI)

313029282726252423222120191817161514131211109876543210
110101010000001100100100xx011111
CRmop2

BTI {<targets>}

SystemHintOp op; if CRm:op2 == '0100 xx0' then op = SystemHintOp_BTI; // Check branch target compatibility between BTI instruction and PSTATE.BTYPE SetBTypeCompatible(BTypeCompatible_BTI(op2<2:1>)); else EndOfInstruction();

Assembler Symbols

<targets>

Is the type of indirection, encoded in op2<2:1>:

op2<2:1> <targets>
00 (omitted)
01 c
10 j
11 jc

Internal version only: isa v32.21, AdvSIMD v29.05, pseudocode v2021-06_xml, sve v2021-06_rc2b ; Build timestamp: 2021-06-28T17:02

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