Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -2284,6 +2284,32 @@
 seq\_cst total orderings of other operations that are not marked
 ``syncscope("singlethread")`` or ``syncscope("<target-scope>")``.
 
+.. _floatenv:
+
+Floating-Point Environment
+--------------------------
+
+The default LLVM floating-point environment assumes that floating-point
+instructions do not have side effects. No floating-point exception state is
+maintained in this environment. Results assume the round-to-nearest rounding
+mode. Therefore, there is no attempt to create or preserve invalid operation
+(SNaN) or division-by-zero exceptions in these examples:
+
+.. code-block:: llvm
+
+      %A = fdiv undef, %X
+      %B = fdiv %X, 0.0
+    Safe:
+      %A = NaN
+      %B = NaN
+
+The benefit of this exception-free assumption is that floating-point
+operations may be speculated freely without any other fast-math relaxations
+to the floating-point model.
+
+Code that requires different behavior than this should use the
+:ref:`Constrained Floating-Point Intrinsics <_constrainedfp>`.
+
 .. _fastmath:
 
 Fast-Math Flags
@@ -12895,6 +12921,8 @@
 Returns another pointer that aliases its argument but which is considered different
 for the purposes of ``load``/``store`` ``invariant.group`` metadata.
 
+.. _constrainedfp:
+
 Constrained Floating Point Intrinsics
 -------------------------------------