diff --git a/Makefile.common b/Makefile.common
index b13db1802d8..eb251b9d622 100644
--- a/Makefile.common
+++ b/Makefile.common
@@ -23,10 +23,22 @@
 #===-----------------------------------------------------------------------====
 
 # These are options that can either be enabled here, or can be enabled on the
-# make command line (make ENABLE_PROFILING=1)
+# make command line (ie, make ENABLE_PROFILING=1)
+#
+
+# When ENABLE_PROFILING is enabled, the llvm source base is built with profile
+# information to allow gprof to be used to get execution frequencies.
 #
 #ENABLE_PROFILING = 1
+
+# When ENABLE_PURIFY is enabled, the LLVM tools are linked with purify (which
+# must be locally installed) to allow for some automated memory error debugging.
+#
 #ENABLE_PURIFY    = 1
+
+# When ENABLE_OPTIMIZED is enabled, Release builds of all of the LLVM code are
+# turned on, and Debug builds are turned off.
+#
 #ENABLE_OPTIMIZED = 1
 
 ifdef SHARED_LIBRARY
diff --git a/Makefile.rules b/Makefile.rules
index b13db1802d8..eb251b9d622 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -23,10 +23,22 @@
 #===-----------------------------------------------------------------------====
 
 # These are options that can either be enabled here, or can be enabled on the
-# make command line (make ENABLE_PROFILING=1)
+# make command line (ie, make ENABLE_PROFILING=1)
+#
+
+# When ENABLE_PROFILING is enabled, the llvm source base is built with profile
+# information to allow gprof to be used to get execution frequencies.
 #
 #ENABLE_PROFILING = 1
+
+# When ENABLE_PURIFY is enabled, the LLVM tools are linked with purify (which
+# must be locally installed) to allow for some automated memory error debugging.
+#
 #ENABLE_PURIFY    = 1
+
+# When ENABLE_OPTIMIZED is enabled, Release builds of all of the LLVM code are
+# turned on, and Debug builds are turned off.
+#
 #ENABLE_OPTIMIZED = 1
 
 ifdef SHARED_LIBRARY