Index: llvm/include/llvm/CodeGen/ISDOpcodes.h
===================================================================
--- llvm/include/llvm/CodeGen/ISDOpcodes.h
+++ llvm/include/llvm/CodeGen/ISDOpcodes.h
@@ -408,17 +408,20 @@
     /// lengths of the input vectors.
     CONCAT_VECTORS,
 
-    /// INSERT_SUBVECTOR(VECTOR1, VECTOR2, IDX) - Returns a vector
-    /// with VECTOR2 inserted into VECTOR1 at the (potentially
-    /// variable) element number IDX, which must be a multiple of the
-    /// VECTOR2 vector length.  The elements of VECTOR1 starting at
-    /// IDX are overwritten with VECTOR2.  Elements IDX through
-    /// vector_length(VECTOR2) must be valid VECTOR1 indices.
+    /// INSERT_SUBVECTOR(VECTOR1, VECTOR2, IDX) - Returns a vector with VECTOR2
+    /// inserted into VECTOR1. Let the type of VECTOR2 be T, then IDX is first
+    /// scaled by the same runtime scaling factor of T to form IDX_0, which
+    /// represents the starting element number at which VECTOR2 will be
+    /// inserted. The elements of VECTOR1 starting at IDX_0 are overwritten with
+    /// VECTOR2. Elements IDX_0 through (IDX_0 + vector_length(VECTOR2) - 1)
+    /// must be valid VECTOR1 indices.
     INSERT_SUBVECTOR,
 
-    /// EXTRACT_SUBVECTOR(VECTOR, IDX) - Returns a subvector from VECTOR (an
-    /// vector value) starting with the element number IDX, which must be a
-    /// constant multiple of the result vector length.
+    /// EXTRACT_SUBVECTOR(VECTOR, IDX) - Returns a subvector from VECTOR.
+    /// Let the result type be T, then IDX is first scaled by the same runtime
+    /// scaling factor of T. The resulting index represents the starting
+    /// element number from which a subvector of type T is extracted.
+    /// IDX must be a constant multiple of T's known minimum vector length.
     EXTRACT_SUBVECTOR,
 
     /// VECTOR_SHUFFLE(VEC1, VEC2) - Returns a vector, of the same type as