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BLR

Branch with Link to Register calls a subroutine at an address in a register, setting register X30 to PC+4.

313029282726252423222120191817161514131211109876543210
1101011000111111000000Rn00000
ZopAMRm

Integer

BLR <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 && !HavePACExt() then UNDEFINED; case op of when '00' branch_type = BranchType_INDIR; when '01' branch_type = BranchType_INDCALL; when '10' branch_type = BranchType_RET; otherwise UNDEFINED; if pac then if Z == '0' && m != 31 then UNDEFINED; if branch_type == BranchType_RET then if n != 31 then UNDEFINED; n = 30; source_is_sp = TRUE;

Assembler Symbols

<Xn>

Is the 64-bit name of the general-purpose register holding the address to be branched to, encoded in the "Rn" field.

Operation

bits(64) target = X[n];[n]; if pac then bits(64) modifier = if source_is_sp then SP[] else X[30] =[m]; if use_key_a then target = AuthIA(target, modifier); else target = AuthIB(target, modifier); if branch_type == BranchType_INDCALL then X[30] = PC[] + 4;[] + 4; // Value in BTypeNext will be used to set PSTATE.BTYPE case branch_type of when BranchToBranchType_INDIR(target,// BR, BRAA, BRAB, BRAAZ, BRABZ if InGuardedPage then if n == 16 || n == 17 then BTypeNext = '01'; else BTypeNext = '11'; else BTypeNext = '01'; when BranchType_INDCALL // BLR, BLRAA, BLRAB, BLRAAZ, BLRABZ BTypeNext = '10'; when BranchType_RET // RET, RETAA, RETAB BTypeNext = '00'; BranchTo);(target, branch_type);


Internal version only: isa v30.44, AdvSIMD v27.08, pseudocode v8.5-2019-06_rc2-5-g22901f2, sve v2019-06_rc4 ; Build timestamp: 2019-06-26T22:3004

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