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Replace two reduces with explicit loops in SIMD implementations. #72423

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Merged
merged 2 commits into from
Mar 20, 2024
Merged

Replace two reduces with explicit loops in SIMD implementations. #72423

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139e6f9
Replace two `reduce`s with explicit loops in SIMD implementations.
stephentyrone Mar 19, 2024
cfa5f54
Spell -0.0 right.
stephentyrone Mar 19, 2024
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14 changes: 12 additions & 2 deletions stdlib/public/core/SIMDVector.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -850,7 +850,11 @@ extension SIMD where Scalar: FixedWidthInteger {
/// Equivalent to `indices.reduce(into: 0) { $0 &+= self[$1] }`.
@_alwaysEmitIntoClient
public func wrappedSum() -> Scalar {
return indices.reduce(into: 0) { $0 &+= self[$1] }
var result: Scalar = 0
for i in indices {
result &+= self[i]
}
return result
}
}

Expand Down Expand Up @@ -927,7 +931,13 @@ extension SIMD where Scalar: FloatingPoint {
// llvm.experimental.vector.reduce.fadd or an explicit tree-sum. Open-
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Nit to past-you: The first line of the implementation note has an elided word, "this eventually" probably needs a "will" or "should" somewhere in there.

// coding the tree sum is problematic, we probably need to define a
// Swift Builtin to support it.
return indices.reduce(into: 0) { $0 += self[$1] }
//
// Use -0 so that LLVM can optimize away initial value + self[0].
var result = -Scalar.zero
for i in indices {
result += self[i]
}
return result
}
}

Expand Down