PVS-Studio

Requested trial license for PVS-Studio. Will try to check C++ code in Swift. Here’s how to generate compile_commands.json needed to run PVS-studio:

swift/utils/build-script <other options> --extra-cmake-options='-DCMAKE_EXPORT_COMPILATION_COMMANDS=ON'

Run PVS-studio analyzer (current directory is swift). Analyzes took 34 hours on my M1 MacBook Pro.

pvs-studio-analyzer analyze -f ../build/Ninja-ReleaseAssert/swift-macosx-arm64/compile_commands.json  -l ~/.config/PVS-Studio/PVS-Studio.lic -o pvs.log

Convert PVS-studio’s log into human readable format:

plog-converter -a GA:1,2 -t tasklist -o project.tasks pvs.log

Experimented with implementing firstIndex(of:) of UnsafeBufferPointer with SIMD. Have to benchmark it to see if it’s better/faster then code generated by library implementation.

extension UnsafeBufferPointer<Int8> {
    func firstIndex(of element: Self.Element) -> Self.Index? {
        //print("count=\(count)")

        guard let pointer = baseAddress else { return nil }
        let address = Int(bitPattern: pointer) // Any guarantee Int is same wide as pointer

        var i = 0
        let stride = MemoryLayout<Int8>.stride // or alignment? jump to Int(bitPattern:) in headers
        let simd4Int8Stride = MemoryLayout<SIMD4<Int8>>.stride
        assert(simd4Int8Stride == stride * SIMD4<Int8>.scalarCount) // Memory layout of SIMD4<Int8> should match one of 4 Int words
        let simd4Int8Sample = SIMD4<Int8>(repeating: element)
        let simd4Int8MaskAllFalse = SIMDMask<SIMD4<Int8>>(arrayLiteral: false, false, false, false) // Why SIMDMask needs SignedInteger?

        // Bytes up to beginning of a SIMD4
        while (address &+ i) % simd4Int8Stride != 0 && i < count {
            guard self[i] != element else { return i }
            i &+= 1
        }

        // Full SIMD4
        // print("Full SIMD4")
        while (i &+ simd4Int8Stride) < count {
            let simd4: SIMD4<Int8> = UnsafePointer(
                bitPattern: address &+ i
            )!/*._unsafelyUnwrappedUnchecked*/.pointee
            //let simd4 = SIMD4<Int8>(array[address+i..<address+i+4])
            // Where is functionality to search for Scalar in SIMD?
            // We have sum(), min(), max() but don't have firstIndex(of: Scalar)
            guard (simd4 .== simd4Int8Sample) == simd4Int8MaskAllFalse else {
                var offset = 0
                while offset < simd4.scalarCount && simd4[offset] != element {
                    offset += 1
                }
                if offset < simd4.scalarCount {
                    return i + offset
                } else {
                    fatalError()
                }
            }
            i &+= simd4Int8Stride
        }

        // Rest bytes up to end
        //print("Rest bytes up to end i=\(i)")
        while i < count {
            guard self[i] != element else { return i }
            i &+= 1
        }

        return nil
    }
}