AArch64: Use simpler sign expressions in Neon intrinsics code - #918
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kirithika7 merged 2 commits intoJul 21, 2026
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Using an expression `(a < b) - (a > 0)` avoids the need for a widening subtraction and subsequent narrowing while producing an identical result. Benchmarking with LLVM 22 on a Neoverse V2 machine, this improves performance on the calSign/saoCuOrg* functions by 6-7%.
This has no performance difference since LLVM 22 already performs the `(-a) | b ==> a - b` optimisation itself, just update the intrinsics to reflect the simpler assembly sequence and to match the previous `sign_diff_neon` change. Change-Id: I5187bbb02f703ec57117a0534701ce5e1ef6ff99
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In
sign_diff_neon, using the expression(a < b) - (a > 0)avoids the need for a widening subtraction and subsequent narrowing while producing an identical result. Benchmarking with LLVM 22 on a Neoverse V2 machine, this improves performance on thecalSign/saoCuOrg*functions by 6-7%.In
signOf_neonthis has no performance difference since LLVM 22 already performs the(-a) | b ==> a - boptimisation itself, so just update the intrinsics to reflect the simpler assembly sequence and to match the previoussign_diff_neonchange.