+Describing Language Specific Properties
+=======================================
+
+When translating a source language to LLVM, finding ways to express concepts and guarantees available in your source language which are not natively provided by LLVM IR will greatly improve LLVM's ability to optimize your code. As an example, C/C++'s ability to mark every add as "no signed wrap (nsw)" goes along way to assisting the optimizer in reasoning about loop induction variables.
+
+The LLVM LangRef includes a number of mechanisms for annotating the IR with additional semantic information. It is *strongly* recommended that you become highly familiar with this document. The list below is intended to highlight a couple of items of particular interest, but is by no means exhaustive.
+
+#. Add nsw/nuw flags as appropriate. Reasoning about overflow is
+ generally hard for an optimizer so providing these facts from the frontend
+ can be very impactful.
+
+#. Use fast-math flags on floating point operations if legal. If you don't
+ need strict IEEE floating point semantics, there are a number of additional
+ optimizations that can be performed. This can be highly impactful for
+ floating point intensive computations.
+
+#. Use inbounds on geps. This can help to disambiguate some aliasing queries.
+
+#. Add noalias/align/dereferenceable/nonnull to function arguments and return
+ values as appropriate
+
+#. Mark functions as readnone/readonly or noreturn/nounwind when known. The
+ optimizer will try to infer these flags, but may not always be able to.
+ Manual annotations are particularly important for external functions that
+ the optimizer can not analyze.
+
+#. Use the lifetime.start/lifetime.end and invariant.start/invariant.end
+ intrinsics where possible. Common profitable uses are for stack like data
+ structures (thus allowing dead store elimination) and for describing
+ life times of allocas (thus allowing smaller stack sizes).
+
+#. Use pointer aliasing metadata, especially tbaa metadata, to communicate
+ otherwise-non-deducible pointer aliasing facts
+
+#. Mark invariant locations using !invariant.load and TBAA's constant flags
+
+#. If you language uses range checks, consider using the IRCE pass. It is not
+ currently part of the standard pass order.
+
+#. For languages with numerous rarely executed guard conditions (e.g. null
+ checks, type checks, range checks) consider adding an extra execution or
+ two of LoopUnswith and LICM to your pass order. The standard pass order,
+ which is tuned for C and C++ applications, may not be sufficient to remove
+ all dischargeable checks from loops.
+
+If you didn't find what you were looking for above, consider proposing an piece of metadata which provides the optimization hint you need. Such extensions are relatively common and are generally well received by the community. You will need to ensure that your proposal is sufficiently general so that it benefits others if you wish to contribute it upstream.