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[hardware] 🐛 Write vd[0] in vslide1up when vl is 1 - #517
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The dispatcher marks a slide-up whose offset is >= vl as a null slide, which also dropped vslide1up/vfslide1up at vl == 1, where vd[0] must still receive the scalar. Those instructions always write vd[0], so they are never null slides. This does not fix the write past vl that pulp-platform#508 also reports. Refs pulp-platform#508 Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com> Signed-off-by: David Harris <David_Harris@hmc.edu>
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Refs #508. The dispatcher marks a slide-up whose offset is >= vl as a null slide, which also dropped
vslide1up/vfslide1upat vl = 1, where vd[0] must still receive the scalar. Those instructions always write vd[0], so they are never null slides. The other defect in #508, writing one element past vl, is not fixed here: with this changevslide1up.vxat vl = 1 writes vd[0] correctly but still overwrites vd[1].Verification (Verilator, NrLanes=4, VLEN=512):
vslide1up.vxat vl = 1 now writes 0x82 to vd[0] (main leaves vd unchanged); vl = 2 and 5 are unchanged, andvslide1down.vxis unaffected.Changelog
Fixed
vslide1up/vfslide1upwhen vl == 1 (vslide1up writes nothing at vl=1 and one element past vl otherwise #508)Checklist