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+# InsTrim
+
+InsTrim: Lightweight Instrumentation for Coverage-guided Fuzzing
+
+## Introduction
+
+InsTrim uses CFG and markers to instrument just what is necessary in the
+binary in llvm_mode. It is about 20-25% faster but as a cost has a lower
+path discovery.
+
+## Usage
+
+Set the environment variable `AFL_LLVM_INSTRIM=1`.
+
+There is also an advanced mode which instruments loops in a way so that
+afl-fuzz can see which loop path has been selected but not being able to
+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`.
+
+## Background
+
+The paper: [InsTrim: Lightweight Instrumentation for Coverage-guided Fuzzing]
+(https://www.ndss-symposium.org/wp-content/uploads/2018/07/bar2018_14_Hsu_paper.pdf)