SVE Instruction List by Dougall Johnson
CLASTA (scalar): Conditionally extract element after last to general-purpose register
CLASTA Xdn, Pg, Xdn, Zm.D (SVE (SME
float64_t svclasta[_n_f64](svbool_t pg, float64_t fallback, svfloat64_t data)
int64_t svclasta[_n_s64](svbool_t pg, int64_t fallback, svint64_t data)
uint64_t svclasta[_n_u64](svbool_t pg, uint64_t fallback, svuint64_t data)
128-bit SVE
Find the last (leftmost) 64-bit element from (2) where the corresponding predicate bit in (1) is non-zero, then set (4) to the next element. If the last corresponding predicate bit is non-zero, set (4) to the first (rightmost) element from (1). If all corresponding predicate bits are zero, preserve the value from (3).
256-bit SVE
Find the last (leftmost) 64-bit element from (2) where the corresponding predicate bit in (1) is non-zero, then set (4) to the next element. If the last corresponding predicate bit is non-zero, set (4) to the first (rightmost) element from (1). If all corresponding predicate bits are zero, preserve the value from (3).
512-bit SVE
Find the last (leftmost) 64-bit element from (2) where the corresponding predicate bit in (1) is non-zero, then set (4) to the next element. If the last corresponding predicate bit is non-zero, set (4) to the first (rightmost) element from (1). If all corresponding predicate bits are zero, preserve the value from (3).
Larger sizes
1024-bit SVE
Find the last (leftmost) 64-bit element from (2) where the corresponding predicate bit in (1) is non-zero, then set (4) to the next element. If the last corresponding predicate bit is non-zero, set (4) to the first (rightmost) element from (1). If all corresponding predicate bits are zero, preserve the value from (3).
2048-bit SVE
Find the last (leftmost) 64-bit element from (2) where the corresponding predicate bit in (1) is non-zero, then set (4) to the next element. If the last corresponding predicate bit is non-zero, set (4) to the first (rightmost) element from (1). If all corresponding predicate bits are zero, preserve the value from (3).
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Inspired by and based on the x86/x64 SIMD Instruction List by Daytime.