diff --git a/include/llvm/Support/SlowOperationInformer.h b/include/llvm/Support/SlowOperationInformer.h
index da6bcbbc618..d05792672ac 100644
--- a/include/llvm/Support/SlowOperationInformer.h
+++ b/include/llvm/Support/SlowOperationInformer.h
@@ -17,9 +17,7 @@
 // appears on the screen (ie, the cursor should be at the start of the line).
 //
 // If the user presses CTRL-C during the operation, the next invocation of the
-// progress method with throw an std::string object indicating that the
-// operation was cancelled.  As such, client code must be exception safe around
-// the progress method.
+// progress method return true indicating that the operation was cancelled.
 //
 // Because SlowOperationInformers fiddle around with signals, they cannot be
 // nested, and interact poorly with threads.  The SIGALRM handler is set back to
@@ -46,19 +44,20 @@ namespace llvm {
     SlowOperationInformer(const std::string &Name);
     ~SlowOperationInformer();
 
-    /// progress - Clients should periodically call this method when they are in
-    /// an exception-safe state.  The Amount variable should indicate how far
+    /// progress - Clients should periodically call this method when they can
+    /// handle cancellation.  The Amount variable should indicate how far
     /// along the operation is, given in 1/10ths of a percent (in other words,
-    /// Amount should range from 0 to 1000).
-    void progress(unsigned Amount);
+    /// Amount should range from 0 to 1000).  If the user cancels the operation,
+    /// this returns true, false otherwise.
+    bool progress(unsigned Amount);
 
     /// progress - Same as the method above, but this performs the division for
     /// you, and helps you avoid overflow if you are dealing with largish
     /// numbers.
-    void progress(unsigned Current, unsigned Maximum) {
+    bool progress(unsigned Current, unsigned Maximum) {
       assert(Maximum != 0 &&
              "Shouldn't be doing work if there is nothing to do!");
-      progress(Current*uint64_t(1000UL)/Maximum);
+      return progress(Current*uint64_t(1000UL)/Maximum);
     }
   };
 } // end namespace llvm
diff --git a/lib/Debugger/ProgramInfo.cpp b/lib/Debugger/ProgramInfo.cpp
index 3bbb0ec9362..66d38f73ca8 100644
--- a/lib/Debugger/ProgramInfo.cpp
+++ b/lib/Debugger/ProgramInfo.cpp
@@ -280,7 +280,8 @@ ProgramInfo::getSourceFiles(bool RequiresCompleteMap) {
   // mapping.
   for (unsigned i = 0, e = TranslationUnits.size(); i != e; ++i) {
     getSourceFile(TranslationUnits[i]);
-    SOI.progress(i+1, e);
+    if (SOI.progress(i+1, e))
+      throw "While building source files index, operation cancelled.";
   }
 
   // Ok, if we got this far, then we indexed the whole program.
@@ -361,7 +362,8 @@ ProgramInfo::getSourceFunctions(bool RequiresCompleteMap) {
   // Loop over all of the functions found, building the SourceFunctions mapping.
   for (unsigned i = 0, e = Functions.size(); i != e; ++i) {
     getFunction(Functions[i]);
-    SOI.progress(i+1, e);
+    if (SOI.progress(i+1, e))
+      throw "While functions index, operation cancelled.";
   }
 
   // Ok, if we got this far, then we indexed the whole program.
diff --git a/lib/Support/SlowOperationInformer.cpp b/lib/Support/SlowOperationInformer.cpp
index 4dafa2c5a1b..bfdfe8808f4 100644
--- a/lib/Support/SlowOperationInformer.cpp
+++ b/lib/Support/SlowOperationInformer.cpp
@@ -37,18 +37,18 @@ SlowOperationInformer::~SlowOperationInformer() {
 /// an exception-safe state.  The Amount variable should indicate how far
 /// along the operation is, given in 1/10ths of a percent (in other words,
 /// Amount should range from 0 to 1000).
-void SlowOperationInformer::progress(unsigned Amount) {
+bool SlowOperationInformer::progress(unsigned Amount) {
   int status = sys::AlarmStatus();
   if (status == -1) {
     std::cout << "\n";
     LastPrintAmount = 0;
-    throw "While " + OperationName + ", operation cancelled.";
+    return true;
   }
 
   // If we haven't spent enough time in this operation to warrant displaying the
   // progress bar, don't do so yet.
   if (status == 0)
-    return;
+    return false;
 
   // Delete whatever we printed last time.
   std::string ToPrint = std::string(LastPrintAmount, '\b');
@@ -62,4 +62,5 @@ void SlowOperationInformer::progress(unsigned Amount) {
 
   LastPrintAmount = OS.str().size();
   std::cout << ToPrint+OS.str() << std::flush;
+  return false;
 }