[PATCH] D67360: [FPEnv] Document that constrained FP intrinsics cannot be mixed with non-constrained

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

kpn updated this revision to Diff 219937.
kpn added a comment.

Address review comment. Mention the possibility of the restrictions mentioned here changing in the future, but don't make any promises.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D67360/new/

https://reviews.llvm.org/D67360

Files:
  docs/LangRef.rst


Index: docs/LangRef.rst
===================================================================
--- docs/LangRef.rst
+++ docs/LangRef.rst
@@ -15051,11 +15051,18 @@
 accurately preserve exception behavior without compromising LLVM's ability to
 optimize FP code when the default behavior is used.
 
+If any FP operation in a function is constrained then they all must be
+constrained. This is required for correct LLVM IR. There are currently no
+FP barrier instructions in LLVM IR, and optimizations that move code around
+can create miscompiles if mixing of constrained and normal operations is
+done. This restriction may be relaxed in the future, but for now must be
+followed.
+
 Each of these intrinsics corresponds to a normal floating-point operation.  The
-first two arguments and the return value are the same as the corresponding FP
+first arguments and the return value are the same as the corresponding FP
 operation.
 
-The third argument is a metadata argument specifying the rounding mode to be
+The next argument is a metadata argument specifying the rounding mode to be
 assumed. This argument must be one of the following strings:
 
 ::
@@ -15086,7 +15093,7 @@
 non-dynamic rounding mode which does not match the actual rounding mode at
 runtime results in undefined behavior.
 
-The fourth argument to the constrained floating-point intrinsics specifies the
+The last argument to the constrained floating-point intrinsics specifies the
 required exception behavior.  This argument must be one of the following
 strings:
 


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