document new environment variables and code format

3 files changed, 24 insertions, 11 deletions

diff --git a/llvm_mode/LLVMInsTrim.so.cc b/llvm_mode/LLVMInsTrim.so.cc
index 0fddad24..229d7d24 100644
--- a/llvm_mode/LLVMInsTrim.so.cc
+++ b/llvm_mode/LLVMInsTrim.so.cc
@@ -54,7 +54,7 @@ struct InsTrim : public ModulePass {
 
  protected:
   std::list<std::string> myWhitelist;
-  uint32_t function_minimum_size = 1;
+  uint32_t               function_minimum_size = 1;
 
  private:
   std::mt19937 generator;
@@ -387,15 +387,18 @@ struct InsTrim : public ModulePass {
 
         }
 
-	if (function_minimum_size < 2) {
+        if (function_minimum_size < 2) {
+
           for (BasicBlock &BB : F) {
-            if (MS.find(&BB) == MS.end()) {
-              continue;
-            }
+
+            if (MS.find(&BB) == MS.end()) { continue; }
             IRBuilder<> IRB(&*BB.getFirstInsertionPt());
             IRB.CreateStore(ConstantInt::get(Int32Ty, genLabel()), OldPrev);
+
           }
+
         }
+
       }
 
       for (BasicBlock &BB : F) {
diff --git a/llvm_mode/MarkNodes.cc b/llvm_mode/MarkNodes.cc
index b8587826..cff6c90a 100644
--- a/llvm_mode/MarkNodes.cc
+++ b/llvm_mode/MarkNodes.cc
@@ -393,10 +393,9 @@ bool MarkSubGraph(uint32_t ss, uint32_t tt) {
     MakeUniq(TopoOrder[i]);
 
   }
-  
-   // Check if there is an empty path.
-  if (NextMarked[tt].count(TopoOrder[0]) > 0)
-    return true;
+
+  // Check if there is an empty path.
+  if (NextMarked[tt].count(TopoOrder[0]) > 0) return true;
   return false;
 
 }
@@ -422,7 +421,7 @@ void MarkVertice() {
 
   timeStamp = 0;
   uint32_t t = 0;
-  bool emptyPathExists = true;
+  bool     emptyPathExists = true;
 
   while (s != t) {
 
@@ -430,10 +429,12 @@ void MarkVertice() {
     t = DominatorTree::idom[t];
 
   }
-  
+
   if (emptyPathExists) {
+
     // Mark all exit blocks to catch the empty path.
     Marked.insert(t_Pred[0].begin(), t_Pred[0].end());
+
   }
 
 }
diff --git a/llvm_mode/README.instrim.md b/llvm_mode/README.instrim.md
index b40dbb18..5c3f32c8 100644
--- a/llvm_mode/README.instrim.md
+++ b/llvm_mode/README.instrim.md
@@ -19,6 +19,15 @@ see how often the loop has been rerun.
 This again is a tradeoff for speed for less path information.
 To enable this mode set `AFL_LLVM_INSTRIM_LOOPHEAD=1`.
 
+There is an additional optimization option that skips single block
+functions. In 95% of the C targets and (guess) 50% of the C++ targets
+it is good to enable this, as otherwise pointless instrumentation occurs.
+The corner case where we want this instrumentation is when vtable/call table
+is used and the index to that vtable/call table is not set in specific
+basic blocks.
+To enable skipping these (most of the time) unnecessary instrumentations set
+`AFL_LLVM_INSTRIM_SKIPSINGLEBLOCK=1`
+
 ## Background
 
 The paper: [InsTrim: Lightweight Instrumentation for Coverage-guided Fuzzing]