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[hardware] 🐛 Fix vrgather out-of-range index hang in the mask unit #477

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[hardware] 🐛 Fix vrgather out-of-range index hang in the mask unit #477

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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -54,6 +54,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
- Force cheshire's sim scripts re-generation
- Fix u-boot to support RVV-linux
- Fixed src emul check for vector integer extension operation
- Fix hang when a vrgather/vrgatherei16 index is out of range

### Added

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6 changes: 5 additions & 1 deletion hardware/src/masku/masku.sv
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Expand Up @@ -1264,7 +1264,11 @@ module masku import ara_pkg::*; import rvv_pkg::*; #(
// VID does not require any operand, while VRGATHER/VCOMPRESS's ALU operand is just preprocessed to get the indices.
// Therefore, VRGATHER/VCOMPRESS's operand are special. Only the vd operand works in the MASKU ALU.
if (!result_queue_full && (&masku_operand_alu_valid || vinsn_issue.op inside {VID,[VRGATHER:VCOMPRESS]})
&& (&masku_operand_vd_valid || (!vinsn_issue.use_vd_op && !(vinsn_issue.op inside {[VRGATHER:VCOMPRESS]})))
// FIX (vrgather OOB hang): an out-of-range VRGATHER/VRGATHEREI16 index reads 0
// (RVV 1.0 §16.4) and the masku never requests vd data for it, so the original
// &masku_operand_vd_valid gate waited forever. Waive vd-valid when the index is OOB.
&& (&masku_operand_vd_valid || (!vinsn_issue.use_vd_op && !(vinsn_issue.op inside {[VRGATHER:VCOMPRESS]}))
|| (vrgat_idx_oor_q && (vinsn_issue.op inside {VRGATHER,VRGATHEREI16})))
&& (&masku_operand_m_valid || vinsn_issue.vm || vinsn_issue.op inside {[VMADC:VMSBC]})
&& (!vrgat_idx_fifo_empty || !(vinsn_issue.op inside {[VRGATHER:VCOMPRESS]}))) begin

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