11 SVE · table lookup
TBL
Each lane picks any element of an eight-entry table — out of range gives zero.
tbl z0.s, { z1.s, z2.s }, z3.sTypes: 32-bit float elements throughout; the indices in z3.s select whole elements. Drawn at SVL = 128 bits, so the two-register table holds 8 entries; at SVL = 512 it holds 32, and out-of-range still zeroes.
z1.s · 0–3
z2.s · 4–7
z3.s
z0.s
z0.s[i] ← table[z3.s[i]], or 0 past the end
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Any element, any lane
The table is two consecutive vectors — eight .s entries here, numbered 0 to 7. Each index lane picks one entry; the order can be arbitrary, reversed, or duplicated.
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Out of range means zero
An index of 8 or more writes 0 into that lane. The zeroing is by design, so missing entries need no masking. The index lanes above run up to 9 — click one and watch its lane go to zero.
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Not length-agnostic
Unlike the rest of SVE, the table size depends on the vector length: code that hard-codes eight entries works only at 128 bits. That rarity is why these index lanes run up to 9.
This pass looks up z3.s = {1, 8, 3, 9} in the table {5, 2, 9, 7} + {4, 8, 1, 6}.