[PATCH] D143074: [LangRef] improve documentation of SNaN in the default FP environment
Sanjay Patel via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Feb 8 06:34:25 PST 2023
spatel updated this revision to Diff 495823.
spatel added a comment.
Patch updated:
Minimized word count and tightened the behavior/expectations for SNaN.
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
@@ -3281,15 +3281,11 @@
Floating-Point Environment
--------------------------
-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.
-
-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.
+The default LLVM floating-point environment assumes that traps are disabled and
+status flags may be set to arbitrary values. Floating-point math operations
+assume that all NaNs are quiet NaNs. Therefore, floating-point math operations
+do not have side effects and may be speculated freely. Results assume the
+round-to-nearest rounding mode.
Code that requires different behavior than this should use the
:ref:`Constrained Floating-Point Intrinsics <constrainedfp>`.
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