From b43e06fa56dd96e6eb3bccc49be71bccae9d2aa1 Mon Sep 17 00:00:00 2001
From: Ted Kremenek <kremenek@apple.com>
Date: Wed, 31 Mar 2010 18:45:04 +0000
Subject: [PATCH] For reverse data flow analyses, enqueue the blocks in reverse
 order. This more likely matches with the ideal order the blocks should be
 visited. This shaves another 1% off the -fsyntax-only time for compare.c
 (403.gcc).

llvm-svn: 100030
---
 .../Analysis/FlowSensitive/DataflowSolver.h   | 21 +++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/clang/include/clang/Analysis/FlowSensitive/DataflowSolver.h b/clang/include/clang/Analysis/FlowSensitive/DataflowSolver.h
index ebfa4e997b82..3c762011a657 100644
--- a/clang/include/clang/Analysis/FlowSensitive/DataflowSolver.h
+++ b/clang/include/clang/Analysis/FlowSensitive/DataflowSolver.h
@@ -196,10 +196,7 @@ private:
   /// SolveDataflowEquations - Perform the actual worklist algorithm
   ///  to compute dataflow values.
   void SolveDataflowEquations(CFG& cfg, bool recordStmtValues) {
-    // Enqueue all blocks to ensure the dataflow values are computed
-    // for every block.  Not all blocks are guaranteed to reach the exit block.
-    for (CFG::iterator I=cfg.begin(), E=cfg.end(); I!=E; ++I)
-      WorkList.enqueue(&**I);
+    EnqueueBlocksOnWorklist(cfg, AnalysisDirTag());
 
     while (!WorkList.isEmpty()) {
       const CFGBlock* B = WorkList.dequeue();
@@ -209,6 +206,22 @@ private:
     }
   }
 
+  void EnqueueBlocksOnWorklist(CFG &cfg, dataflow::forward_analysis_tag) {
+    // Enqueue all blocks to ensure the dataflow values are computed
+    // for every block.  Not all blocks are guaranteed to reach the exit block.
+    for (CFG::iterator I=cfg.begin(), E=cfg.end(); I!=E; ++I)
+      WorkList.enqueue(&**I);
+  }
+
+  void EnqueueBlocksOnWorklist(CFG &cfg, dataflow::backward_analysis_tag) {
+    // Enqueue all blocks to ensure the dataflow values are computed
+    // for every block.  Not all blocks are guaranteed to reach the exit block.
+    // Enqueue in reverse order since that will more likely match with
+    // the order they should ideally processed by the dataflow algorithm.
+    for (CFG::reverse_iterator I=cfg.rbegin(), E=cfg.rend(); I!=E; ++I)
+      WorkList.enqueue(&**I);
+  }
+
   void ProcessMerge(CFG& cfg, const CFGBlock* B) {
     ValTy& V = TF.getVal();
     TF.SetTopValue(V);