[PATCH] D67839: [FPEnv] Document requirement of function attributes with constrained floating point

[Kevin P. Neal via Phabricator via llvm-commits]

kpn updated this revision to Diff 221804.
kpn added a comment.

Update for review comments. Eliminate verbiage about noimplicitfloat. Add mention of strictfp preventing the addition of potentially trapping instructions.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67839/new/

https://reviews.llvm.org/D67839

Files:
  llvm/docs/LangRef.rst


Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -1786,7 +1786,8 @@
     requires strict floating-point semantics.  LLVM will not attempt any
     optimizations that require assumptions about the floating-point rounding
     mode or that might alter the state of floating-point status flags that
-    might otherwise be set or cleared by calling this function.
+    might otherwise be set or cleared by calling this function. LLVM will
+    not introduce any new floating-point instructions that may trap.
 ``"thunk"``
     This attribute indicates that the function will delegate to some other
     function with a tail call. The prototype of a thunk should not be used for
@@ -15148,6 +15149,17 @@
 vectorized into a single instruction that raises each unique exception a single
 time.
 
+Required Function Attributes:
+"""""""""""""""""""""""""""""
+
+Proper :ref:`function attributes <fnattrs>` usage is required for the
+constrained intrinsics to function correctly.
+
+All function *calls* done in a function that uses constrained floating
+point intrinsics must have the ``strictfp`` attribute.
+
+All function *definitions* that use constrained floating point intrinsics
+must have the ``strictfp`` attribute.
 
 '``llvm.experimental.constrained.fadd``' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


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