Implement inline assembly add for all architectures and bump swift-tools-version to 6.1

Author: marcprux

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version: 5.9
+// swift-tools-version: 6.1
 import PackageDescription
 
 let package = Package(

README.md

@@ -57,7 +57,7 @@ and add the `skipstone` plugin in order for Skip to generate gradle build for th
 
 
 ```swift
-// swift-tools-version: 5.9
+// swift-tools-version: 6.1
 import PackageDescription
 
 let package = Package(

Sources/LibCLibrary/src/demo.c

@@ -20,18 +20,32 @@ short add_with_assembly(short a, short b) {
     short result;
 
     #if __aarch64__ // ARM 64-bit
-    asm volatile ("add %w[a], %w[a], %w[b]; mov %w[a], %w[result]"
+    // add the two source W (32-bit) registers, writing the sum to the result register
+    asm ("add %w[result], %w[a], %w[b]"
                 : [result] "=r" (result)
-                : [a] "r" (a), [b] "r" (b)
-                : "cc");
+                : [a] "r" (a), [b] "r" (b));
     #elif __i386__ // Intel 32-bit
-    result = a + b;
+    // tie `a` into the result register, then add `b` into it (AT&T order: addw src, dst)
+    asm ("addw %[b], %[result]"
+                : [result] "=r" (result)
+                : [b] "r" (b), "0" (a)
+                : "cc");
     #elif __x86_64__ // Intel 64-bit
-    result = a + b;
+    // tie `a` into the result register, then add `b` into it (AT&T order: addw src, dst)
+    asm ("addw %[b], %[result]"
+                : [result] "=r" (result)
+                : [b] "r" (b), "0" (a)
+                : "cc");
     #elif __arm__ // ARM 32-bit
-    result = a + b;
-    #elif __riscv_64 // RISC-V 64-bit (future)
-    result = a + b;
+    // add Rn (a) and Rm (b), writing the sum to Rd (result)
+    asm ("add %[result], %[a], %[b]"
+                : [result] "=r" (result)
+                : [a] "r" (a), [b] "r" (b));
+    #elif defined(__riscv) && (__riscv_xlen == 64) // RISC-V 64-bit (future)
+    // add rs1 (a) and rs2 (b), writing the sum to rd (result)
+    asm ("add %[result], %[a], %[b]"
+                : [result] "=r" (result)
+                : [a] "r" (a), [b] "r" (b));
     #else
     #error "Unsupported architecture"
     #endif

Sources/SkipCDemo/SkipCDemo.swift

@@ -9,7 +9,7 @@ import LibCLibrary
 /// `DemoLibrary` is a Swift encapsulation of the embedded C library's functions and structures.
 internal final class DemoLibrary {
     /// The singleton library instance, registered using JNA to map the Kotlin functions to their native equivalents
-    static let instance = registerNatives(DemoLibrary(), frameworkName: "SkipCDemo", libraryName: "clibrary")
+    nonisolated(unsafe) static let instance = registerNatives(DemoLibrary(), frameworkName: "SkipCDemo", libraryName: "clibrary")
 
     // Functions marked with "SKIP EXTERN" will eliminate the bodies and
     // mark the transpiled Kotlin functions as "extern",

Tests/SkipCDemoTests/SkipCDemoTests.swift

@@ -4,7 +4,7 @@ import XCTest
 import Foundation
 @testable import SkipCDemo
 
-fileprivate let lib: DemoLibrary = DemoLibrary.instance
+nonisolated(unsafe) fileprivate let lib: DemoLibrary = DemoLibrary.instance
 
 final class SkipCDemoTests: XCTestCase {
     func testSkipCDemo() throws {