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Adds IR level PGO Instrumentation options #1992

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5c8c159
Add ir and cs instrumentation options
chiragramani Sep 16, 2025
4edf9dd
Update Options.swift
chiragramani Oct 20, 2025
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89 changes: 76 additions & 13 deletions Sources/SwiftDriver/Driver/Driver.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -3307,24 +3307,87 @@ extension Driver {
}
}

static private func validateProfilingGenerateArgs(
_ parsedOptions: inout ParsedOptions,
diagnosticEngine: DiagnosticsEngine
) {
let genFlags: [Option] = [
.profileGenerate,
.irProfileGenerate,
.csProfileGenerate,
.csProfileGenerateEq,
]

var providedGen = genFlags.filter { parsedOptions.hasArgument($0) }
if parsedOptions.hasArgument(.csProfileGenerate),
parsedOptions.hasArgument(.csProfileGenerateEq)
{
// If both forms were specified, report a clear conflict.
diagnosticEngine.emit(
.error(Error.conflictingOptions(.csProfileGenerate, .csProfileGenerateEq)),
location: nil
)
providedGen.removeAll { $0 == .csProfileGenerateEq }
}

guard providedGen.count >= 2 else { return }
for i in 1..<providedGen.count {
let error = Error.conflictingOptions(providedGen[i - 1], providedGen[i])
diagnosticEngine.emit(.error(error), location: nil)
}
Comment on lines +3338 to +3341
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@drodriguez drodriguez Nov 10, 2025

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Minor: any reason for this not being similar to the C++ driver?

for i in 0..<(providedGen.count - 1) {
  for j in (i + 1)..<providedGen.count {
    let error = Error.conflictingOptions(providedGen[i], providedGen[j])
    diagnosticEngine.emit(.error(error), location: nil)
  }
}

Edit: I did not realize that you were might have been moving around existing code. @kavon might be able to answer this better, but maybe what might have worked for them and only 3 flags might not work as well for 5 flags (and when the flags do not mix gen and use like in their case).

}

static private func validateProfilingUseArgs(
_ parsedOptions: inout ParsedOptions,
diagnosticEngine: DiagnosticsEngine
) {
let conflictingGenFlags: [Option] = [
.profileGenerate,
.irProfileGenerate,
]
let useProfArgs: [Option] = [
.profileUse,
.profileSampleUse,
]
let providedUse = useProfArgs.filter { parsedOptions.hasArgument($0) }
guard !providedUse.isEmpty else { return }

// At most one *use* option allowed
if providedUse.count > 1 {
for i in 0..<(providedUse.count - 1) {
for j in (i + 1)..<providedUse.count {
Comment on lines +3363 to +3364
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@drodriguez drodriguez Nov 10, 2025

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Thinking that maybe is easier to understand (and to repeat here and above), if one uses enumerated():

for (i, left) in providedUse.enumerated() {
  for (j, right) in providedUse.enumerated() {
    guard i < j else { continue }
    diagnosticEngine.emit(.error(Error.conflictingOptions(left, right)), location: nil)
  }
}

diagnosticEngine.emit(
.error(Error.conflictingOptions(providedUse[i], providedUse[j])),
location: nil
)
}
}
}

// If no generate flags, we're good.
let providedGen = conflictingGenFlags.filter { parsedOptions.hasArgument($0) }
guard !providedGen.isEmpty else { return }

// We already diagnosed if the user passed more than one "use" option
// (e.g. both `-profile-use` and `-profile-sample-use`). To avoid
// spamming diagnostics, we now treat the first provided "use" flag
// as the canonical representative.
let canonicalUse = providedUse[0]

// Generate vs Use are mutually exclusive
for g in providedGen {
diagnosticEngine.emit(.error(Error.conflictingOptions(g, canonicalUse)), location: nil)
}
}


static func validateProfilingArgs(_ parsedOptions: inout ParsedOptions,
fileSystem: FileSystem,
workingDirectory: AbsolutePath?,
diagnosticEngine: DiagnosticsEngine) {
let conflictingProfArgs: [Option] = [.profileGenerate,
.profileUse,
.profileSampleUse]

// Find out which of the mutually exclusive profiling arguments were provided.
let provided = conflictingProfArgs.filter { parsedOptions.hasArgument($0) }

// If there's at least two of them, there's a conflict.
if provided.count >= 2 {
for i in 1..<provided.count {
let error = Error.conflictingOptions(provided[i-1], provided[i])
diagnosticEngine.emit(.error(error), location: nil)
}
}
validateProfilingGenerateArgs(&parsedOptions, diagnosticEngine: diagnosticEngine)
validateProfilingUseArgs(&parsedOptions, diagnosticEngine: diagnosticEngine)

// Ensure files exist for the given paths.
func checkForMissingProfilingData(_ profileDataArgs: [String]) {
Expand Down
4 changes: 1 addition & 3 deletions Sources/SwiftDriver/Jobs/DarwinToolchain+LinkerSupport.swift
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Expand Up @@ -258,9 +258,7 @@ extension DarwinToolchain {
fileSystem: fileSystem
)

if parsedOptions.hasArgument(.profileGenerate) {
commandLine.appendFlag("-fprofile-generate")
}
Comment on lines -261 to -263
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@ellishg ellishg Sep 17, 2025

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This feels like a bug to me. As I understand, Swift's -profile-generate flag does front-end instrumentation, and is different from Clang's -fprofile-generate.

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@chiragramani chiragramani Sep 18, 2025

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this behavior is existing in swift-driver today, and I’m a bit wary of changing it here because there may be tests and downstream flows that rely on it. This PR is primarily adding the new pieces, that said, if you feel it’s worth addressing this legacy behavior in the same PR, please let me know and I can look into it.

commandLine.appendFlags(mapInstrumentationTypeToClangArgs(from: &parsedOptions))

// These custom arguments should be right before the object file at the
// end.
Expand Down
3 changes: 3 additions & 0 deletions Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift
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Expand Up @@ -237,6 +237,9 @@ extension Driver {
try commandLine.appendLast(.RpassMissedEQ, from: &parsedOptions)
try commandLine.appendLast(.suppressWarnings, from: &parsedOptions)
try commandLine.appendLast(.profileGenerate, from: &parsedOptions)
try commandLine.appendLast(.irProfileGenerate, from: &parsedOptions)
try commandLine.appendLast(.csProfileGenerate, from: &parsedOptions)
try commandLine.appendLast(.csProfileGenerateEq, from: &parsedOptions)
try commandLine.appendLast(.profileUse, from: &parsedOptions)
try commandLine.appendLast(.profileCoverageMapping, from: &parsedOptions)
try commandLine.appendLast(.debugInfoForProfiling, from: &parsedOptions)
Expand Down
2 changes: 1 addition & 1 deletion Sources/SwiftDriver/Jobs/GenericUnixToolchain+LinkerSupport.swift
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Expand Up @@ -303,7 +303,7 @@ extension GenericUnixToolchain {
}
}

if parsedOptions.hasArgument(.profileGenerate) {
if needsInstrumentedProfile(from: &parsedOptions) {
let environment = (targetTriple.environment == .android) ? "-android" : ""
let libProfile = VirtualPath.lookup(targetInfo.runtimeResourcePath.path)
.appending(components: "clang", "lib", targetTriple.osNameUnversioned,
Expand Down
2 changes: 1 addition & 1 deletion Sources/SwiftDriver/Jobs/WebAssemblyToolchain+LinkerSupport.swift
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Expand Up @@ -176,7 +176,7 @@ extension WebAssemblyToolchain {
commandLine.appendFlag("-fsanitize=\(sanitizerNames)")
}

if parsedOptions.hasArgument(.profileGenerate) {
if needsInstrumentedProfile(from: &parsedOptions) {
let libProfile = VirtualPath.lookup(targetInfo.runtimeResourcePath.path)
.appending(components: "clang", "lib", targetTriple.osName,
"libclang_rt.profile-\(targetTriple.archName).a")
Expand Down
7 changes: 4 additions & 3 deletions Sources/SwiftDriver/Jobs/WindowsToolchain+LinkerSupport.swift
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Expand Up @@ -50,7 +50,7 @@ extension WindowsToolchain {
// for now, which supports the behavior via a flag.
// TODO: Once we've changed coverage to no longer rely on emitting
// duplicate weak symbols (rdar://131295678), we can remove this.
if parsedOptions.hasArgument(.profileGenerate) { return true }
if needsInstrumentedProfile(from: &parsedOptions) { return true }

return false
}()
Expand Down Expand Up @@ -228,11 +228,12 @@ extension WindowsToolchain {
commandLine.appendFlag("-fsanitize=\(sanitize)")
}

if parsedOptions.contains(.profileGenerate) {
if needsInstrumentedProfile(from: &parsedOptions) {
assert(bForceLLD,
"LLD is currently required for profiling (rdar://131295678)")

commandLine.appendFlag("-fprofile-generate")
commandLine.appendFlags(mapInstrumentationTypeToClangArgs(from: &parsedOptions))

// FIXME(rdar://131295678): Currently profiling requires the ability to
// emit duplicate weak symbols. Assume we're using lld and pass
// `-lld-allow-duplicate-weak` to enable this behavior.
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26 changes: 26 additions & 0 deletions Sources/SwiftDriver/Toolchains/Toolchain.swift
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Expand Up @@ -376,6 +376,32 @@ extension Toolchain {
}
return clangArg
}

internal func mapInstrumentationTypeToClangArgs(from options: inout ParsedOptions) -> [String] {
var args: [String] = []

if options.contains(.profileGenerate) || options.contains(.irProfileGenerate) {
args.append("-fprofile-generate")
}

if options.contains(.csProfileGenerate) {
args.append("-fcs-profile-generate")
}

if options.contains(.csProfileGenerateEq),
let path = options.getLastArgument(.csProfileGenerateEq)?.asSingle {
args.append("-fcs-profile-generate=\(path)")
}

return args
}

internal func needsInstrumentedProfile(from parsedOptions: inout ParsedOptions) -> Bool {
parsedOptions.contains(.profileGenerate) ||
parsedOptions.contains(.irProfileGenerate) ||
parsedOptions.contains(.csProfileGenerate) ||
parsedOptions.contains(.csProfileGenerateEq)
}
}

@_spi(Testing) public enum ToolchainError: Swift.Error {
Expand Down
6 changes: 6 additions & 0 deletions Sources/SwiftOptions/Options.swift
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Expand Up @@ -776,6 +776,9 @@ extension Option {
public static let printZeroStats: Option = Option("-print-zero-stats", .flag, attributes: [.helpHidden, .frontend], helpText: "Prints all stats even if they are zero")
public static let profileCoverageMapping: Option = Option("-profile-coverage-mapping", .flag, attributes: [.frontend, .noInteractive], helpText: "Generate coverage data for use with profiled execution counts")
public static let profileGenerate: Option = Option("-profile-generate", .flag, attributes: [.frontend, .noInteractive], helpText: "Generate instrumented code to collect execution counts")
public static let irProfileGenerate: Option = Option("-ir-profile-generate", .flag, attributes: [.frontend, .noInteractive], helpText: "Generate instrumented code to collect execution counts into default.profraw (overridden by LLVM_PROFILE_FILE env var)")
public static let csProfileGenerate: Option = Option("-cs-profile-generate", .flag, attributes: [.frontend, .noInteractive], helpText: "Generate instrumented code to collect context sensitive execution counts into default.profraw (overridden by LLVM_PROFILE_FILE env var)")
public static let csProfileGenerateEq: Option = Option("-cs-profile-generate=", .joined, attributes: [.frontend, .noInteractive, .argumentIsPath], metaVar: "<dir>", helpText: "Generate instrumented code to collect context sensitive execution counts into <directory>/default.profraw (overridden by LLVM_PROFILE_FILE env var)")
public static let profileSampleUse: Option = Option("-profile-sample-use=", .joined, attributes: [.frontend, .noInteractive, .argumentIsPath], metaVar: "<profile data>", helpText: "Supply sampling-based profiling data from llvm-profdata to enable profile-guided optimization")
public static let profileStatsEntities: Option = Option("-profile-stats-entities", .flag, attributes: [.helpHidden, .frontend], helpText: "Profile changes to stats in -stats-output-dir, subdivided by source entity")
public static let profileStatsEvents: Option = Option("-profile-stats-events", .flag, attributes: [.helpHidden, .frontend], helpText: "Profile changes to stats in -stats-output-dir")
Expand Down Expand Up @@ -1749,6 +1752,9 @@ extension Option {
Option.printZeroStats,
Option.profileCoverageMapping,
Option.profileGenerate,
Option.irProfileGenerate,
Option.csProfileGenerate,
Option.csProfileGenerateEq,
Option.profileSampleUse,
Option.profileStatsEntities,
Option.profileStatsEvents,
Expand Down
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