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Zacas follow-up: fix amocas.q store and gate Zacas-only logic - #1915
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rosethompson merged 2 commits intoOct 6, 2026
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Default synthesis does no boundary optimization, so Zacas control signals that cross module boundaries leave their logic behind even when Zacas is not supported. Gate the amocas select in the AMO ALU, the LSU's use of AMOCASPairM, and the datapath's rs2-port borrow and compare/swap registers with P.ZACAS_SUPPORTED. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Signed-off-by: David Harris <David_Harris@hmc.edu>
w64 treated any funct3 whose low bits were not 11 as narrower than 64 bits, so amocas.q (funct3 100) sign-extended bit 31 across the low doubleword it stores after a successful compare. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Signed-off-by: David Harris <David_Harris@hmc.edu>
rosethompson
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Oct 6, 2026
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#1880 merged before two changes landed. On RV64,
amoalutreatedamocas.q(funct3 100) as a narrow access and sign-extended bit 31 across the low doubleword it stores, which ImperasDV lockstep caught on the read-back. The second commit gates the Zacas logic that other modules keep without Zacas, since default synthesis does no boundary optimization, as discussed on #1880. With both, all 72 Zacas, ZacasZabha, Zabha, and Zaamo ACT tests pass on rv64gc and rv32gc andamocas.qis lockstep-clean; those tests need the ACT cvwsail.jsonmain-memoryatomic_supportraised toAMOCASQ(rv64gc) orAMOCASD(rv32gc), or Sail traps every amocas.🤖 Generated with Claude Code