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+# laf-intel instrumentation
+
+## Introduction
+
+This originally is the work of an individual nicknamed laf-intel.
+His blog [Circumventing Fuzzing Roadblocks with Compiler Transformations]
+(https://lafintel.wordpress.com/) and gitlab repo [laf-llvm-pass]
+(https://gitlab.com/laf-intel/laf-llvm-pass/)
+describe some code transformations that
+help afl++ to enter conditional blocks, where conditions consist of
+comparisons of large values.
+
+## Usage
+
+By default these passes will not run when you compile programs using 
+afl-clang-fast. Hence, you can use AFL as usual.
+To enable the passes you must set environment variables before you
+compile the target project.
+
+The following options exist:
+
+`export AFL_LLVM_LAF_SPLIT_SWITCHES=1`
+
+Enables the split-switches pass.
+
+`export AFL_LLVM_LAF_TRANSFORM_COMPARES=1`
+
+Enables the transform-compares pass (strcmp, memcmp, strncmp,
+strcasecmp, strncasecmp).
+
+`export AFL_LLVM_LAF_SPLIT_COMPARES=1`
+
+Enables the split-compares pass.
+By default it will 
+1. simplify operators >= (and <=) into chains of > (<) and == comparisons
+2. change signed integer comparisons to a chain of sign-only comparison
+and unsigned integer comparisons
+3. split all unsigned integer comparisons with bit widths of
+64, 32 or 16 bits to chains of 8 bits comparisons.
+
+You can change the behaviour of the last step by setting
+`export AFL_LLVM_LAF_SPLIT_COMPARES_BITW=<bit_width>`, where 
+bit_width may be 64, 32 or 16. For example, a bit_width of 16
+would split larger comparisons down to 16 bit comparisons.
+
+A new experimental feature is splitting floating point comparisons into a
+series of sign, exponent and mantissa comparisons followed by splitting each
+of them into 8 bit comparisons when necessary.
+It is activated with the `AFL_LLVM_LAF_SPLIT_FLOATS` setting.
+Please note that full IEEE 754 functionality is not preserved, that is
+values of nan and infinity will probably behave differently.
+
+Note that setting this automatically activates `AFL_LLVM_LAF_SPLIT_COMPARES`
+
+You can also set `AFL_LLVM_LAF_ALL` and have all of the above enabled :-)
+