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Adds IR level PGO Instrumentation options #1992

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97 changes: 84 additions & 13 deletions Sources/SwiftDriver/Driver/Driver.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -3334,24 +3334,91 @@ extension Driver {
}
}

static private func validateProfilingGenerateArgs(
_ parsedOptions: inout ParsedOptions,
diagnosticEngine: DiagnosticsEngine
) {
let genFlags: [Option] = [
.profileGenerate,
.irProfileGenerate,
.irProfileGenerateEQ,
.csProfileGenerate,
.csProfileGenerateEQ,
]
func resolveDualFormConflict(_ plain: Option, _ equalsForm: Option) {
if parsedOptions.hasArgument(plain),
parsedOptions.hasArgument(equalsForm)
{
diagnosticEngine.emit(
.error(Error.conflictingOptions(plain, equalsForm)),
location: nil
)
providedGen.removeAll { $0 == equalsForm }
}
}

var providedGen = genFlags.filter { parsedOptions.hasArgument($0) }
resolveDualFormConflict(.irProfileGenerate, .irProfileGenerateEQ)
resolveDualFormConflict(.csProfileGenerate, .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)
}
}

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

// At most one *use* option allowed
if providedUse.count > 1 {
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)
}
}
}

// 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 All @@ -3376,6 +3443,10 @@ extension Driver {
if let profileSampleUseArg = parsedOptions.getLastArgument(.profileSampleUse)?.asSingle {
checkForMissingProfilingData([profileSampleUseArg])
}

if let irProfileUseArgs = parsedOptions.getLastArgument(.irProfileUse)?.asMultiple {
checkForMissingProfilingData(irProfileUseArgs)
}
}

static func validateParseableOutputArgs(_ parsedOptions: inout ParsedOptions,
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
5 changes: 5 additions & 0 deletions Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift
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Expand Up @@ -243,6 +243,11 @@ 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(.irProfileGenerateEQ, from: &parsedOptions)
try commandLine.appendLast(.irProfileUse, from: &parsedOptions)
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@cachemeifyoucan cachemeifyoucan Nov 10, 2025

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This is a flag that points to the file. It needs path remapping if needed. Use addPathOption.

Also means this is not handled correctly in swift-frontend/scanner. See the comment I added to the other review.

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@chiragramani chiragramani Nov 14, 2025

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Thanks @cachemeifyoucan for looking into it. Are you suggesting something as follows

 if let irProfileUsePath = parsedOptions.getLastArgument(.irProfileUse)?.asMultiple.last {
      try addPathOption(option: .irProfileUse,
                        path: VirtualPath(path: irProfileUsePath),
                        to: &commandLine,
                        remap: jobNeedPathRemap)
    }

On trying the above, I get a fatalError in CommandLineArguments.appendFlag function

fatalError("Option cannot be appended as a flag: \(option)")

I think the option .irProfileUse is of .commaJoined similar to existing flag: profileUse and would also have the same issue, do you any suggestions on how to go about it?

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@chiragramani chiragramani Nov 21, 2025

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Hey @cachemeifyoucan / @drodriguez ,
Can you guide me on how to go about addressing this crash please?

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@drodriguez drodriguez Nov 21, 2025

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I don't understand the why of the request from @cachemeifyoucan . I cannot help with that. .profileUse is also a .commaJoined flag, and it is following the same pattern a couple of lines below. Seems that it has not been a problem until now, so not sure why it should be a problem to follow this pattern now. When the addPathOption was introduced a couple of years ago it seemed to be fine to not change .profileUse.

I think addPathOption is probably not directly usable here because if I understand correctly .commaJoined means that you can add several paths into a single argument separated by commas, and addPathOption is not prepared for that (or for adding several paths). It sounds like one has to write special code to do the same thing that's happening in addPathOption when the flags are .commaJoined, which does whatever is needed with VirtualPath for each element of the input argument (not only the .last).

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.
Expand Down
37 changes: 37 additions & 0 deletions Sources/SwiftDriver/Toolchains/Toolchain.swift
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Expand Up @@ -376,6 +376,43 @@ 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(.irProfileGenerateEQ),
let path = options.getLastArgument(.irProfileGenerateEQ)?.asSingle {
args.append("-fprofile-generate=\(path)")
}

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)")
}

if options.contains(.irProfileUse),
let path = options.getLastArgument(.irProfileUse)?.asMultiple.last {
args.append("-fprofile-use=\(path)")
}

return args
}

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

@_spi(Testing) public enum ToolchainError: Swift.Error {
Expand Down
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