[LangRef] nnan and ninf produce poison.
Clarify that violating nnan and ninf can lead to undefined behavior.
This allows more aggressive optimizations based on those assumptions.
Differential Revision: https://reviews.llvm.org/D47963
llvm-svn: 337323
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 1f4641c..4dc010d 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -2350,13 +2350,13 @@
``nnan``
No NaNs - Allow optimizations to assume the arguments and result are not
- NaN. Such optimizations are required to retain defined behavior over
- NaNs, but the value of the result is undefined.
+ NaN. If an argument is a nan, or the result would be a nan, it produces
+ a :ref:`poison value <poisonvalues>` instead.
``ninf``
No Infs - Allow optimizations to assume the arguments and result are not
- +/-Inf. Such optimizations are required to retain defined behavior over
- +/-Inf, but the value of the result is undefined.
+ +/-Inf. If an argument is +/-Inf, or the result would be +/-Inf, it
+ produces a :ref:`poison value <poisonvalues>` instead.
``nsz``
No Signed Zeros - Allow optimizations to treat the sign of a zero