From ccb6d1ea0cfc1c9f2e0ea651414ff80610fa12dc Mon Sep 17 00:00:00 2001
From: Ted Kremenek <kremenek@apple.com>
Date: Sat, 4 May 2013 01:13:05 +0000
Subject: [PATCH] [analyzer; alternate edges] - merge control edges where we
 descend to a subexpression and pop back out.

llvm-svn: 181085
---
 clang/lib/StaticAnalyzer/Core/BugReporter.cpp | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/clang/lib/StaticAnalyzer/Core/BugReporter.cpp b/clang/lib/StaticAnalyzer/Core/BugReporter.cpp
index b3c0dac9646d..827bf09b05f3 100644
--- a/clang/lib/StaticAnalyzer/Core/BugReporter.cpp
+++ b/clang/lib/StaticAnalyzer/Core/BugReporter.cpp
@@ -1802,6 +1802,26 @@ static bool optimizeEdges(PathPieces &path,
       hasChanges = true;
       continue;
     }
+
+    // Rule II.
+    //
+    // If we have two consecutive control edges where we decend to a
+    // subexpression and then pop out merge them.
+    //
+    // NOTE: this will be limited later in cases where we add barriers
+    // to prevent this optimization.
+    //
+    // For example:
+    //
+    // (1.1 -> 1.1.1) -> (1.1.1 -> 1.2) becomes (1.1 -> 1.2).
+    if (level1 && level2 &&
+        level1 == level4 &&
+        level2 == level3 && PM.getParent(level2) == level1) {
+      PieceI->setEndLocation(PieceNextI->getEndLocation());
+      path.erase(NextI);
+      hasChanges = true;
+      continue;
+    }
   }
 
   // No changes.