[PATCH] D143074: [LangRef] improve documentation of SNaN in the default FP environment

[Sanjay Patel via Phabricator via llvm-commits]

spatel updated this revision to Diff 493975.
spatel added a comment.

Updated:

1. Avoid controversy by not using the term "undef".
2. Make it clearer that math ops may not quiet an SNaN (intentionally avoiding the use of "set" or "clear" of bits).


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D143074/new/

https://reviews.llvm.org/D143074

Files:
  llvm/docs/LangRef.rst


Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -3284,8 +3284,10 @@
 The default LLVM floating-point environment assumes that floating-point
 instructions do not have side effects. Results assume the round-to-nearest
 rounding mode. No floating-point exception state is maintained in this
-environment. Therefore, there is no attempt to create or preserve invalid
-operation (SNaN) or division-by-zero exceptions.
+environment. Therefore, there is no attempt to create, clear, or preserve
+exceptions. There is also no attempt to set/clear the signaling bit of NaN
+values as specified by IEEE-754. In particular, math operations may not
+quiet a signaling NaN.
 
 The benefit of this exception-free assumption is that floating-point
 operations may be speculated freely without any other fast-math relaxations


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