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Port --global-base option for WebAssembly from legacy driver #1539

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Merged
merged 1 commit into from
Feb 3, 2024
Merged

Port --global-base option for WebAssembly from legacy driver #1539

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11 changes: 11 additions & 0 deletions Sources/SwiftDriver/Jobs/WebAssemblyToolchain+LinkerSupport.swift
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Expand Up @@ -137,6 +137,17 @@ extension WebAssemblyToolchain {
// Explicitly pass the target to the linker
commandLine.appendFlag("--target=\(targetTriple.triple)")

// WebAssembly doesn't reserve low addresses as its ABI. But without
// "extra inhabitants" of the pointer representation, runtime performance
// and memory footprint are significantly degraded. So we reserve the
// low addresses to use them as extra inhabitants by telling the lowest
// valid address to the linker.
// The value of lowest valid address, called "global base", must be always
// synchronized with `SWIFT_ABI_WASM32_LEAST_VALID_POINTER` defined in
// apple/swift's runtime library.
commandLine.appendFlag(.Xlinker)
commandLine.appendFlag("--global-base=4096")

// Delegate to Clang for sanitizers. It will figure out the correct linker
// options.
guard sanitizers.isEmpty else {
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1 change: 1 addition & 0 deletions Tests/SwiftDriverTests/SwiftDriverTests.swift
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Expand Up @@ -2315,6 +2315,7 @@ final class SwiftDriverTests: XCTestCase {
XCTAssertTrue(commandContainsTemporaryPath(cmd, "bar.o"))
XCTAssertTrue(commandContainsTemporaryResponsePath(cmd, "Test.autolink"))
XCTAssertTrue(cmd.contains(.responseFilePath(.absolute(path.appending(components: "wasi", "static-executable-args.lnk")))))
XCTAssertTrue(cmd.contains(subsequence: [.flag("-Xlinker"), .flag("--global-base=4096")]))
XCTAssertTrue(cmd.contains(.flag("-O3")))
XCTAssertEqual(linkJob.outputs[0].file, try VirtualPath(path: "Test"))

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