Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -24952,7 +24952,12 @@
 bit mask where each bit specifies floating-point class to test. For example, the
 value 0x108 makes test for normal value, - bits 3 and 8 in it are set, which
 means that the function returns ``true`` if ``op`` is a positive or negative
-normal value. The function never raises floating-point exceptions.
+normal value. The function never raises floating-point exceptions. The
+function does not canonicalize its input value and does not depend
+on the floating-point environment. If the floating-point environment
+has a zeroing treatment of subnormal input values (such as indicated
+by the ``"denormal-fp-math"`` attribute), a subnormal value will be
+observed (will not be implicitly treated as zero).
 
 
 General Intrinsics