Index: llvm/trunk/test/tools/llvm-profdata/input-dir.test
===================================================================
--- llvm/trunk/test/tools/llvm-profdata/input-dir.test
+++ llvm/trunk/test/tools/llvm-profdata/input-dir.test
@@ -0,0 +1,22 @@
+# Create an input file.
+RUN: echo "#" > %t.input
+RUN: echo "%t.dir1" >> %t.input
+RUN: echo "2,%t.dir2" >> %t.input
+
+RUN: mkdir -p %t.dir1
+RUN: mkdir -p %t.dir2/subdir
+
+RUN: echo ' ' > %t.dir1/bar
+RUN: echo ' ' > %t.dir1/foo
+RUN: echo ' ' > %t.dir2/bar
+RUN: echo ' ' > %t.dir2/foo
+RUN: echo ' ' > %t.dir2/subdir/baz
+
+RUN: llvm-profdata merge -f %t.input -dump-input-file-list -o /dev/null | FileCheck %s
+RUN: llvm-profdata merge -weighted-input=2,%t.dir2 -dump-input-file-list -o /dev/null %t.dir1 | FileCheck %s
+
+CHECK: 1,{{.*}}.dir1/bar
+CHECK-NEXT: 1,{{.*}}.dir1/foo
+CHECK-NEXT: 2,{{.*}}.dir2/bar
+CHECK-NEXT: 2,{{.*}}.dir2/foo
+CHECK-NEXT: 2,{{.*}}.dir2/subdir/baz
Index: llvm/trunk/test/tools/llvm-profdata/input-filenames.test
===================================================================
--- llvm/trunk/test/tools/llvm-profdata/input-filenames.test
+++ llvm/trunk/test/tools/llvm-profdata/input-filenames.test
@@ -1,17 +1,19 @@
 # Create an input file.
 RUN: echo '# comment 1' > %t.input
 RUN: echo ' # comment 2' >> %t.input
-RUN: echo 'bar' >> %t.input
-RUN: echo ' baz' >> %t.input
+RUN: echo " %t.bar" >> %t.input
+RUN: echo " %t.baz" >> %t.input
 RUN: echo "2,%t.weighted" >> %t.input
 
-# Create the weighted file, since these actually need to exist.
 RUN: echo ' ' > %t.weighted
+RUN: echo ' ' > %t.foo
+RUN: echo ' ' > %t.bar
+RUN: echo ' ' > %t.baz
 
-RUN: llvm-profdata merge -f %t.input -dump-input-file-list -o /dev/null foo | FileCheck %s
-RUN: llvm-profdata merge -input-files %t.input -dump-input-file-list -o /dev/null foo | FileCheck %s
+RUN: llvm-profdata merge -f %t.input -dump-input-file-list -o /dev/null %t.foo | FileCheck %s
+RUN: llvm-profdata merge -input-files %t.input -dump-input-file-list -o /dev/null %t.foo | FileCheck %s
 
-CHECK: 1,foo
-CHECK-NEXT: 1,bar
-CHECK-NEXT: 1,baz
+CHECK: 1,{{.*}}.foo
+CHECK-NEXT: 1,{{.*}}.bar
+CHECK-NEXT: 1,{{.*}}.baz
 CHECK-NEXT: 2,{{.*}}.weighted
Index: llvm/trunk/tools/llvm-profdata/llvm-profdata.cpp
===================================================================
--- llvm/trunk/tools/llvm-profdata/llvm-profdata.cpp
+++ llvm/trunk/tools/llvm-profdata/llvm-profdata.cpp
@@ -109,12 +109,12 @@
 }
 
 struct WeightedFile {
-  StringRef Filename;
+  std::string Filename;
   uint64_t Weight;
 
   WeightedFile() {}
 
-  WeightedFile(StringRef F, uint64_t W) : Filename{F}, Weight{W} {}
+  WeightedFile(const std::string &F, uint64_t W) : Filename{F}, Weight{W} {}
 };
 typedef SmallVector<WeightedFile, 5> WeightedFileVector;
 
@@ -305,10 +305,6 @@
   if (WeightStr.getAsInteger(10, Weight) || Weight < 1)
     exitWithError("Input weight must be a positive integer.");
 
-  if (!sys::fs::exists(FileName))
-    exitWithErrorCode(make_error_code(errc::no_such_file_or_directory),
-                      FileName);
-
   return WeightedFile(FileName, Weight);
 }
 
@@ -324,6 +320,33 @@
   return std::move(*BufOrError);
 }
 
+static void addWeightedInput(WeightedFileVector &WNI, const WeightedFile &WF) {
+  StringRef Filename = WF.Filename;
+  uint64_t Weight = WF.Weight;
+  llvm::sys::fs::file_status Status;
+  llvm::sys::fs::status(Filename, Status);
+  if (!llvm::sys::fs::exists(Status))
+    exitWithErrorCode(make_error_code(errc::no_such_file_or_directory),
+                      Filename);
+  // If it's a source file, collect it.
+  if (llvm::sys::fs::is_regular_file(Status)) {
+    WNI.emplace_back(Filename, Weight);
+    return;
+  }
+
+  if (llvm::sys::fs::is_directory(Status)) {
+    std::error_code EC;
+    for (llvm::sys::fs::recursive_directory_iterator F(Filename, EC), E;
+         F != E && !EC; F.increment(EC)) {
+      if (llvm::sys::fs::is_regular_file(F->path())) {
+        addWeightedInput(WNI, {F->path(), Weight});
+      }
+    }
+    if (EC)
+      exitWithErrorCode(EC, Filename);
+  }
+}
+
 static void parseInputFilenamesFile(MemoryBuffer *Buffer,
                                     WeightedFileVector &WFV) {
   if (!Buffer)
@@ -339,9 +362,9 @@
       continue;
     // If there's no comma, it's an unweighted profile.
     else if (SanitizedEntry.find(',') == StringRef::npos)
-      WFV.emplace_back(SanitizedEntry, 1);
+      addWeightedInput(WFV, {SanitizedEntry, 1});
     else
-      WFV.emplace_back(parseWeightedFile(SanitizedEntry));
+      addWeightedInput(WFV, parseWeightedFile(SanitizedEntry));
   }
 }
 
@@ -387,9 +410,9 @@
 
   WeightedFileVector WeightedInputs;
   for (StringRef Filename : InputFilenames)
-    WeightedInputs.emplace_back(Filename, 1);
+    addWeightedInput(WeightedInputs, {Filename, 1});
   for (StringRef WeightedFilename : WeightedInputFilenames)
-    WeightedInputs.emplace_back(parseWeightedFile(WeightedFilename));
+    addWeightedInput(WeightedInputs, parseWeightedFile(WeightedFilename));
 
   // Make sure that the file buffer stays alive for the duration of the
   // weighted input vector's lifetime.