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Cortex-A8 R2P2.pdf - ARM Information Center

Cortex-A8 R2P2.pdf - ARM Information Center

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Instruction Cycle TimingTable 16-4 shows the operation of multiply instructions.Table 16-4 Multiply instructionsMultiply type Cycles Source1 Source2 Source3 Source4 Result1 Result2Normal: MUL 2 Rm:E1 Rs:E1 [Rd:E3] {Rn:E4} a Rd:E5 -Long: SMULL, UMULL 3 Rm:E1 Rs:E1 {[RdLo:E3]} {[RdHi:E3]} RdLo:E5 RdHi:E5Long: SMLAL, UMLAL, UMAAL 3 Rm:E1 Rs:E1 {[RdLo:E2]} {[RdHi:E1]} RdLo:E5 RdHi:E5Halfword: SMLAxy,SMULxy2 Rm:E1 Rs:E1 [Rd:E2] {Rn:E4} a Rd:E5 -Halfword: SMLALxy 2 Rm:E1 Rs:E1 {[RdLo:E1]} {[RdHi:E2]} RdLo:E5 RdHi:E5Word-halfword: SMULWy 1 Rm:E1 Rs:E1 [Rd:E2] - Rd:E5 -Word-halfword: SMLAWy 2 Rm:E1 Rs:E1 [Rd:E2] Rn:E4 a Rd:E5 -Most significant word 2 Rm:E1 Rs:E1 [Rd:E3] {Rn:E4} a Rd:E5 -Dual halfword: SMUAD,SMUSDDual halfword: SMLAD,SMLSDDual halfword:SMLALD, SMLSLD1 Rm:E1 Rs:E1 [Rd:E2] - Rd:E5 -2 Rm:E1 Rs:E1 [Rd:E2] {Rn:E4} a Rd:E5 -2 Rm:E1 Rs:E1 {[RdLo:E1]} {[RdHi:E2]} RdLo:E5 RdHi:E5a. A multiply that is followed by a MAC with a dependency on the accumulator, Rn register, triggers a special accumulatorforwarding. This enables both instructions to issue back-to-back because Rn is required as a source in E4. If this accumulatorforwarding is not used, Rn is required in E2.16.2.4 Parallel arithmetic and DSP instructionsThe parallel arithmetic instructions include ADD15, ADDSUBX, SUBADDX, SUB16, ADD8, SUB8,QDADD, QDSUB, QADD, QSUB.<strong>ARM</strong> DDI 0344E Copyright © 2006-2008 <strong>ARM</strong> Limited. All rights reserved. 16-7

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