[Driver] Clear deferred commands on each task queue iteration.

Author: graydon

lib/Driver/Compilation.cpp

@@ -222,9 +222,11 @@ namespace driver {
     }
 
     /// When a task finishes, check other Jobs that may be blocked.
-    void markFinished(const Job *Cmd) {
+    void markFinished(const Job *Cmd, bool Skipped=false) {
       if (Comp.ShowIncrementalBuildDecisions) {
-        llvm::outs() << "Job finished: " << LogJob(Cmd) << "\n";
+        llvm::outs() << "Job "
+                     << (Skipped ? "skipped" : "finished")
+                     << ": " << LogJob(Cmd) << "\n";
       }
       FinishedCommands.insert(Cmd);
 
@@ -590,8 +592,9 @@ namespace driver {
           }
 
           ScheduledCommands.insert(Cmd);
-          markFinished(Cmd);
+          markFinished(Cmd, /*Skipped=*/true);
         }
+        DeferredCommands.clear();
 
         // ...which may allow us to go on and do later tasks.
       } while (Result == 0 && TQ->hasRemainingTasks());

test/Driver/Dependencies/Inputs/only-skip-once/file1.swift

@@ -0,0 +1,3 @@
+public class Class1 {
+  public var Var1 : Int?
+}

test/Driver/Dependencies/Inputs/only-skip-once/file2.swift

@@ -0,0 +1,3 @@
+public class Class2 {
+  public var Var2c : Class1?
+}

test/Driver/Dependencies/Inputs/only-skip-once/main.swift

@@ -0,0 +1,2 @@
+var x = Class1()
+var y = Class2()

test/Driver/Dependencies/Inputs/only-skip-once/output-file-map.json

@@ -0,0 +1,23 @@
+{
+  "": {
+    "swift-dependencies": "master.swiftdeps"
+  },
+  "main.swift": {
+    "dependencies": "main.d",
+    "object": "main.o",
+    "swiftmodule": "main~partial.swiftmodule",
+    "swift-dependencies": "main.swiftdeps"
+  },
+  "file1.swift": {
+    "dependencies": "file1.d",
+    "object": "file1.o",
+    "swiftmodule": "file1~partial.swiftmodule",
+    "swift-dependencies": "file1.swiftdeps"
+  },
+  "file2.swift": {
+    "dependencies": "file2.d",
+    "object": "file2.o",
+    "swiftmodule": "file2~partial.swiftmodule",
+    "swift-dependencies": "file2.swiftdeps"
+  }
+}

test/Driver/Dependencies/only-skip-once.swift

@@ -0,0 +1,21 @@
+// XFAIL: linux
+// RUN: rm -rf %t && cp -r %S/Inputs/only-skip-once/ %t
+// RUN: touch -t 201401240005 %t/*
+
+// RUN: cd %t && %swiftc_driver -driver-show-incremental -output-file-map %t/output-file-map.json -incremental main.swift file1.swift file2.swift -j1 2>&1 | %FileCheck -check-prefix=CHECK-INITIAL %s
+
+// CHECK-INITIAL-NOT: warning
+// CHECK-INITIAL: Job finished: {compile: main.o <= main.swift}
+// CHECK-INITIAL: Job finished: {compile: file1.o <= file1.swift}
+// CHECK-INITIAL: Job finished: {compile: file2.o <= file2.swift}
+// CHECK-INITIAL: Job finished: {link: main <= main.o file1.o file2.o}
+
+// RUN: touch -t 201401240006 %t/file2.swift
+// RUN: cd %t && %swiftc_driver -driver-show-incremental -output-file-map %t/output-file-map.json -incremental main.swift file1.swift file2.swift -j1 2>&1 | %FileCheck -check-prefix=CHECK-REBUILD %s
+
+// We should skip the main and file1 rebuilds here, but we should only note skipping them _once_
+// CHECK-REBUILD: Job finished: {compile: file2.o <= file2.swift}
+// CHECK-REBUILD: Job skipped: {compile: main.o <= main.swift}
+// CHECK-REBUILD: Job skipped: {compile: file1.o <= file1.swift}
+// CHECK-REBUILD: Job finished: {link: main <= main.o file1.o file2.o}
+// CHECK-REBUILD-NOT: Job skipped: