Merge pull request #34231 from CodaFi/skippy

Skip Merge-Modules When We Can

Author: CodaFi

include/swift/Driver/Action.h

@@ -130,23 +130,40 @@ class JobAction : public Action {
 class IncrementalJobAction : public JobAction {
 public:
   struct InputInfo {
-    enum Status {
+    /// The status of an input known to the driver. These are used to affect
+    /// the scheduling decisions made during an incremental build.
+    ///
+    /// \Note The order of cases matters. They are ordered from least to
+    /// greatest impact on the incremental build schedule.
+    enum class Status {
+      /// The input to this job is up to date.
       UpToDate,
-      NeedsCascadingBuild,
+      /// The input to this job has changed in a way that requires this job to
+      /// be rerun, but not in such a way that it requires a cascading rebuild.
       NeedsNonCascadingBuild,
+      /// The input to this job has changed in a way that requires this job to
+      /// be rerun, and in such a way that all jobs dependent upon this one
+      /// must be scheduled as well.
+      NeedsCascadingBuild,
+      /// The input to this job was not known to the driver when it was last
+      /// run.
       NewlyAdded
     };
 
   public:
-    Status status = UpToDate;
+    Status status = Status::UpToDate;
     llvm::sys::TimePoint<> previousModTime;
 
     InputInfo() = default;
     InputInfo(Status stat, llvm::sys::TimePoint<> time)
         : status(stat), previousModTime(time) {}
 
     static InputInfo makeNewlyAdded() {
-      return InputInfo(Status::NewlyAdded, llvm::sys::TimePoint<>::max());
+      return {Status::NewlyAdded, llvm::sys::TimePoint<>::max()};
+    }
+
+    static InputInfo makeNeedsCascadingRebuild() {
+      return {Status::NeedsCascadingBuild, llvm::sys::TimePoint<>::min()};
     }
   };
 
@@ -166,7 +183,8 @@ class IncrementalJobAction : public JobAction {
 
 public:
   static bool classof(const Action *A) {
-    return A->getKind() == Action::Kind::CompileJob;
+    return A->getKind() == Action::Kind::CompileJob ||
+           A->getKind() == Action::Kind::MergeModuleJob;
   }
 };
 
@@ -263,12 +281,12 @@ class REPLJobAction : public JobAction {
   }
 };
 
-class MergeModuleJobAction : public JobAction {
+class MergeModuleJobAction : public IncrementalJobAction {
   virtual void anchor() override;
 public:
-  MergeModuleJobAction(ArrayRef<const Action *> Inputs)
-      : JobAction(Action::Kind::MergeModuleJob, Inputs,
-                  file_types::TY_SwiftModuleFile) {}
+  MergeModuleJobAction(ArrayRef<const Action *> Inputs, InputInfo input)
+      : IncrementalJobAction(Action::Kind::MergeModuleJob, Inputs,
+                             file_types::TY_SwiftModuleFile, input) {}
 
   static bool classof(const Action *A) {
     return A->getKind() == Action::Kind::MergeModuleJob;

lib/Driver/Compilation.cpp

@@ -446,7 +446,7 @@ namespace driver {
 
     std::vector<const Job*>
     reloadAndRemarkDeps(const Job *FinishedCmd, int ReturnCode,
-                             const bool forRanges) {
+                        const bool forRanges) {
       const CommandOutput &Output = FinishedCmd->getOutput();
       StringRef DependenciesFile =
           Output.getAdditionalOutputForType(file_types::TY_SwiftDeps);
@@ -458,7 +458,8 @@ namespace driver {
         // coarse dependencies that always affect downstream nodes), but we're
         // not using either of those right now, and this logic should probably
         // be revisited when we are.
-        assert(FinishedCmd->getCondition() == Job::Condition::Always);
+        assert(isa<MergeModuleJobAction>(FinishedCmd->getSource()) ||
+               FinishedCmd->getCondition() == Job::Condition::Always);
         return {};
       }
       const bool compileExitedNormally =
@@ -907,6 +908,7 @@ namespace driver {
         return everyIncrementalJob;
       };
 
+      const Job *mergeModulesJob = nullptr;
       CommandSet jobsToSchedule;
       CommandSet initialCascadingCommands;
       for (const Job *cmd : Comp.getJobs()) {
@@ -915,6 +917,11 @@ namespace driver {
           continue;
         }
 
+        if (isa<MergeModuleJobAction>(cmd->getSource())) {
+          assert(!mergeModulesJob && "multiple scheduled merge-modules jobs?");
+          mergeModulesJob = cmd;
+        }
+
         const Optional<std::pair<bool, bool>> shouldSchedAndIsCascading =
             computeShouldInitiallyScheduleJobAndDependendents(cmd, forRanges);
         if (!shouldSchedAndIsCascading)
@@ -936,6 +943,15 @@ namespace driver {
            collectIncrementalExternallyDependentJobsFromDependencyGraph(
                forRanges))
         jobsToSchedule.insert(cmd);
+
+      // The merge-modules job is special: it *must* be scheduled if any other
+      // job has been scheduled because any other job can influence the
+      // structure of the resulting module. Additionally, the initial scheduling
+      // predicate above is only aware of intra-module changes. External
+      // dependencies changing *must* cause merge-modules to be scheduled.
+      if (!jobsToSchedule.empty() && mergeModulesJob) {
+        jobsToSchedule.insert(mergeModulesJob);
+      }
       return jobsToSchedule;
     }
 
@@ -1031,6 +1047,13 @@ namespace driver {
     /// But returns None if there was a dependency read error.
     Optional<std::pair<Job::Condition, bool>>
     loadDependenciesAndComputeCondition(const Job *const Cmd, bool forRanges) {
+      // merge-modules Jobs do not have .swiftdeps files associated with them,
+      // however, their compilation condition is computed as a function of their
+      // inputs, so their condition can be used as normal.
+      if (isa<MergeModuleJobAction>(Cmd->getSource())) {
+        return std::make_pair(Cmd->getCondition(), true);
+      }
+
       // Try to load the dependencies file for this job. If there isn't one, we
       // always have to run the job, but it doesn't affect any other jobs. If
       // there should be one but it's not present or can't be loaded, we have to
@@ -1163,7 +1186,12 @@ namespace driver {
           continue;
         }
 
-        // Can we run a cross-module incremental build at all? If not, fallback.
+        // Is this module out of date? If not, just keep searching.
+        if (Comp.getLastBuildTime() >= depStatus.getLastModificationTime())
+          continue;
+
+        // Can we run a cross-module incremental build at all?
+        // If not, fall back.
         if (!Comp.getEnableCrossModuleIncrementalBuild()) {
           fallbackToExternalBehavior(external);
           continue;
@@ -1609,8 +1637,8 @@ namespace driver {
           CompileJobAction::InputInfo info;
           info.previousModTime = entry.first->getInputModTime();
           info.status = entry.second ?
-            CompileJobAction::InputInfo::NeedsCascadingBuild :
-            CompileJobAction::InputInfo::NeedsNonCascadingBuild;
+            CompileJobAction::InputInfo::Status::NeedsCascadingBuild :
+            CompileJobAction::InputInfo::Status::NeedsNonCascadingBuild;
           inputs[&inputFile->getInputArg()] = info;
         }
       }
@@ -1627,7 +1655,7 @@ namespace driver {
 
           CompileJobAction::InputInfo info;
           info.previousModTime = entry->getInputModTime();
-          info.status = CompileJobAction::InputInfo::UpToDate;
+          info.status = CompileJobAction::InputInfo::Status::UpToDate;
           inputs[&inputFile->getInputArg()] = info;
         }
       }

lib/Driver/CompilationRecord.h

@@ -59,12 +59,12 @@ inline static StringRef getName(TopLevelKey Key) {
 inline static StringRef
 getIdentifierForInputInfoStatus(CompileJobAction::InputInfo::Status Status) {
   switch (Status) {
-  case CompileJobAction::InputInfo::UpToDate:
+  case CompileJobAction::InputInfo::Status::UpToDate:
     return "";
-  case CompileJobAction::InputInfo::NewlyAdded:
-  case CompileJobAction::InputInfo::NeedsCascadingBuild:
+  case CompileJobAction::InputInfo::Status::NewlyAdded:
+  case CompileJobAction::InputInfo::Status::NeedsCascadingBuild:
     return "!dirty";
-  case CompileJobAction::InputInfo::NeedsNonCascadingBuild:
+  case CompileJobAction::InputInfo::Status::NeedsNonCascadingBuild:
     return "!private";
   }
 
@@ -76,11 +76,11 @@ getIdentifierForInputInfoStatus(CompileJobAction::InputInfo::Status Status) {
 /// compilation record file (.swiftdeps file).
 inline static Optional<CompileJobAction::InputInfo::Status>
 getInfoStatusForIdentifier(StringRef Identifier) {
-  return llvm::StringSwitch<Optional<
-      CompileJobAction::InputInfo::Status>>(Identifier)
-    .Case("", CompileJobAction::InputInfo::UpToDate)
-    .Case("!dirty", CompileJobAction::InputInfo::NeedsCascadingBuild)
-    .Case("!private", CompileJobAction::InputInfo::NeedsNonCascadingBuild)
+  using InputStatus = CompileJobAction::InputInfo::Status;
+  return llvm::StringSwitch<Optional<InputStatus>>(Identifier)
+    .Case("", InputStatus::UpToDate)
+    .Case("!dirty", InputStatus::NeedsCascadingBuild)
+    .Case("!private", InputStatus::NeedsNonCascadingBuild)
     .Default(None);
 }