[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 494000.
spatel added a comment.

Soften the wording - rather than "no attempt", we offer "no guarantee" about the value of the signaling bit.


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 guarantee that the signaling bit of NaN values
+changes 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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