Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -24882,7 +24882,12 @@
 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 read canonicalized values, 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