[polly] r210753 - Check for an empty error log.

[Andreas Simbuerger]

Author: simbuerg
Date: Thu Jun 12 02:25:08 2014
New Revision: 210753

URL: http://llvm.org/viewvc/llvm-project?rev=210753&view=rev
Log:
Check for an empty error log.

Fixes #19976.

The error log does not contain an error, in case we reject a candidate
without generating a diagnostic message by using invalid<>(...). This is
the case for the top-level region of a function.

The patch comes without a test-case because adding a useful one requires
additional code just for triggering it. Before the patch it would only trigger,
if we try to print the CFG with Scop error annotations.

Modified:
    polly/trunk/lib/Analysis/ScopDetection.cpp

Modified: polly/trunk/lib/Analysis/ScopDetection.cpp
URL: http://llvm.org/viewvc/llvm-project/polly/trunk/lib/Analysis/ScopDetection.cpp?rev=210753&r1=210752&r2=210753&view=diff
==============================================================================
--- polly/trunk/lib/Analysis/ScopDetection.cpp (original)
+++ polly/trunk/lib/Analysis/ScopDetection.cpp Thu Jun 12 02:25:08 2014
@@ -219,7 +219,14 @@ std::string ScopDetection::regionIsInval
   // Get the first error we found. Even in keep-going mode, this is the first
   // reason that caused the candidate to be rejected.
   RejectLog Errors = RejectLogs.at(R);
-  return (*Errors.begin())->getMessage();
+
+  // This can happen when we marked a region invalid, but didn't track
+  // an error for it.
+  if (Errors.size() == 0)
+    return "";
+
+  RejectReasonPtr RR = *Errors.begin();
+  return RR->getMessage();
 }
 
 bool ScopDetection::isValidCFG(BasicBlock &BB,