From b4c2d54fee5a287a0afbb2851e6438a474917d84 Mon Sep 17 00:00:00 2001
From: trevor_hansen <trevor_hansen@e59a4935-1847-0410-ae03-e826735625c1>
Date: Sat, 29 May 2010 05:04:50 +0000
Subject: [PATCH] Simplifyin BVSX to CONCAT if the topmost bit of the thing
 being extended is known.

git-svn-id: https://stp-fast-prover.svn.sourceforge.net/svnroot/stp-fast-prover/trunk/stp@800 e59a4935-1847-0410-ae03-e826735625c1
---
 src/simplifier/simplifier.cpp | 15 ++++++++++++++-
 src/simplifier/simplifier.h   |  2 ++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/simplifier/simplifier.cpp b/src/simplifier/simplifier.cpp
index 21a6031..9f23495 100644
--- a/src/simplifier/simplifier.cpp
+++ b/src/simplifier/simplifier.cpp
@@ -2158,9 +2158,22 @@ namespace BEEV
           if (a0.GetValueWidth() == len)
             {
               //nothing to signextend
-              return a0;
+              output =  a0;
+              break;
             }
 
+          // If the msb is known. Then puts 0's or the 1's infront.
+          if (mostSignificantConstants(a0) > 0)
+          {
+        	  if (getConstantBit(a0,0) == 0)
+        		  output = _bm->CreateTerm(BVCONCAT, len, _bm->CreateZeroConst(len-a0.GetValueWidth()), a0);
+        	  else
+        		  output = _bm->CreateTerm(BVCONCAT, len, _bm->CreateMaxConst(len-a0.GetValueWidth()), a0);
+
+        	  break;
+          }
+
+
           switch (a0.GetKind())
             {
             case BVCONST:
diff --git a/src/simplifier/simplifier.h b/src/simplifier/simplifier.h
index bda86df..9b64944 100644
--- a/src/simplifier/simplifier.h
+++ b/src/simplifier/simplifier.h
@@ -46,6 +46,7 @@ namespace BEEV
     //Ptr to STP Manager
     STPMgr * _bm;
 
+    NodeFactory * nf;
   public:
       
     /****************************************************************
@@ -61,6 +62,7 @@ namespace BEEV
       ASTTrue  = bm->CreateNode(TRUE);
       ASTFalse = bm->CreateNode(FALSE);
       ASTUndefined = bm->CreateNode(UNDEFINED);
+      nf = bm->defaultNodeFactory;
     }
       
     ~Simplifier()
-- 
2.47.3