From 496b09a3771f7b607ddbaac9e0824d9ea7bbb3f1 Mon Sep 17 00:00:00 2001
From: Reijo Tomperi <aggro80@users.sourceforge.net>
Date: Sun, 21 Dec 2008 19:24:21 +0000
Subject: [PATCH] Remove reduntant if sentences that are never executed.

---
 testtokenize.cpp |   2 +-
 tokenize.cpp     | 122 +++++++++++++++++++++++++++++++++++++++++++++++
 tokenize.h       |   7 +++
 3 files changed, 130 insertions(+), 1 deletion(-)

diff --git a/testtokenize.cpp b/testtokenize.cpp
index 27f5bfa27..1c1bc07dc 100644
--- a/testtokenize.cpp
+++ b/testtokenize.cpp
@@ -217,7 +217,7 @@ private:
         std::ostringstream ostr;
         for (const TOKEN *tok = tokenizer.tokens(); tok; tok = tok->next())
             ostr << " " << tok->str();
-        ASSERT_EQUALS( std::string(" void f ( ) { if ( true ) ; }"), ostr.str() );
+        ASSERT_EQUALS( std::string(" void f ( ) { ; }"), ostr.str() );
     }
 
     void simplify_known_variables()
diff --git a/tokenize.cpp b/tokenize.cpp
index 63bd42d5f..508ed7fe2 100644
--- a/tokenize.cpp
+++ b/tokenize.cpp
@@ -1033,10 +1033,132 @@ void Tokenizer::simplifyTokenList()
         modified |= simplifyCasts();
         modified |= simplifyFunctionReturn();
         modified |= simplifyKnownVariables();
+        modified |= removeReduntantConditions();
     }
 }
 //---------------------------------------------------------------------------
 
+bool Tokenizer::removeReduntantConditions()
+{
+    bool ret = false;
+
+    for ( TOKEN *tok = _tokens; tok; tok = tok->next() )
+    {
+        if (!TOKEN::Match(tok, "if ( %bool% )"))
+            continue;
+
+        // Find matching else
+        const TOKEN *elseTag = 0;
+        if( TOKEN::Match( tok->tokAt( 4 ), "{" ) )
+        {
+            // Find the closing "}"
+            int indentLevel = 0;
+            for ( const TOKEN *closing = tok->tokAt( 5 ); closing; closing = closing->next() )
+            {
+                if( TOKEN::Match( closing, "{" ) )
+                {
+                    indentLevel++;
+                    continue;
+                }
+
+                if( TOKEN::Match( closing, "}" ) )
+                    indentLevel--;
+
+                if( indentLevel >= 0 )
+                    continue;
+
+                // Closing } is found.
+                elseTag = closing->next();
+                break;
+            }
+        }
+        else
+        {
+            // Find the closing ";"
+            for ( const TOKEN *closing = tok->tokAt( 4 ); closing; closing = closing->next() )
+            {
+                if( TOKEN::Match( closing, ";" ) )
+                {
+                    elseTag = closing->next();
+                    break;
+                }
+            }
+        }
+
+        bool boolValue = false;
+        if( tok->tokAt( 2 )->str() == "true" )
+            boolValue = true;
+
+        if( elseTag && TOKEN::Match( elseTag, "else" ) )
+        {
+            if( TOKEN::Match( elseTag->next(), "if" ) )
+            {
+                // Handle "else if"
+                if( boolValue == false )
+                {
+                    // Convert "if( false ) {aaa;} else if() {bbb;}" => "if() {bbb;}"
+                    TOKEN::eraseTokens( tok, elseTag->tokAt( 1 ) );
+                    ret = true;
+                }
+                else
+                {
+                    // Keep first if, remove every else if and else after it
+
+                    // TODO, implement
+                }
+            }
+            else
+            {
+                // Handle else
+                if( boolValue == false )
+                {
+                    // Convert "if( false ) {aaa;} else {bbb;}" => "{bbb;}" or ";{bbb;}"
+                    if( tok->previous() )
+                        tok = tok->previous();
+                    else
+                        tok->setstr( ";" );
+
+                    TOKEN::eraseTokens( tok, elseTag->tokAt( 1 ) );
+                    ret = true;
+                }
+                else
+                {
+                    // Convert "if( true ) {aaa;} else {bbb;}" => "{aaa;}"
+
+                    // TODO, implement
+                }
+            }
+        }
+        else
+        {
+            // Handle if without else
+            if( boolValue == false )
+            {
+                // Remove if and its content
+                if( tok->previous() )
+                    tok = tok->previous();
+                else
+                    tok->setstr( ";" );
+
+                TOKEN::eraseTokens( tok, elseTag );
+            }
+            else
+            {
+                // convert "if( true ) {aaa;}" => "{aaa;}"
+                if( tok->previous() )
+                    tok = tok->previous();
+                else
+                    tok->setstr( ";" );
+
+                TOKEN::eraseTokens( tok, tok->tokAt( 5 ) );
+            }
+
+            ret = true;
+        }
+    }
+
+    return ret;
+}
 
 bool Tokenizer::simplifyConditions()
 {
diff --git a/tokenize.h b/tokenize.h
index e31af952a..76345146a 100644
--- a/tokenize.h
+++ b/tokenize.h
@@ -101,6 +101,13 @@ private:
      */
     bool simplifyConditions();
 
+    /** Remove reduntant code, e.g. if( false ) { int a; } should be
+     * removed, because it is never executed.
+     * @return true if something is modified
+     *         false if nothing is done.
+     */
+    bool removeReduntantConditions();
+
     /** Simplify casts
      * @return true if something is modified
      *         false if nothing is done.