Add Swift using SIMD

Earthfile

@@ -96,6 +96,7 @@ collect-data:
   BUILD +sbcl
   BUILD +scala
   BUILD +swift
+  BUILD +swift-simd
   BUILD +zig
 
 all:
@@ -388,6 +389,13 @@ swift:
   RUN --no-cache swiftc leibniz.swift -O -o leibniz -clang-target native -lto=llvm-full
   DO +BENCH --name="swift" --lang="Swift" --version="swift --version" --cmd="./leibniz"
 
+swift-simd:
+  FROM swift:5.7-jammy
+  DO +PREPARE_DEBIAN
+  DO +ADD_FILES --src="leibniz-simd.swift"
+  RUN --no-cache swiftc leibniz-simd.swift -O -o leibniz -clang-target native -lto=llvm-full
+  DO +BENCH --name="swift" --lang="Swift" --version="swift --version" --cmd="./leibniz"
+
 zig:
   # On 3.16 there is no zig package, but on edge there is
   FROM alpine:edge

src/leibniz-simd.swift

@@ -0,0 +1,28 @@
+import Foundation
+
+let text = try! String(contentsOfFile: "rounds.txt").split(separator: "\n")[0]
+var rounds = UInt(text)!
+
+var pi: Double = 1.0
+
+let roundsRemainder = rounds % 4
+rounds -= roundsRemainder
+
+rounds += 2 // do this outside the loop
+
+var i: UInt = 2
+while i < rounds {
+    let xVec = SIMD4<Double>(-1.0, 1.0, -1.0, 1.0)
+    let iVec = SIMD4<Double>(Double(i) + 0, Double(i) + 1, Double(i) + 2, Double(i) + 3)
+    pi += (xVec / (2.0 * iVec - 1.0)).sum()
+    i += 4
+}
+
+for _ in 0..<roundsRemainder {
+    let x = -1.0 + 2.0 * Double(i & 1)
+    pi += x / Double(2 * i - 1)
+    i += 1
+}
+
+pi *= 4.0
+print(String(format: "%.16f", pi))