diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -6825,7 +6825,9 @@
     param: 4, offset: [0, 5][, calls: ((Callee)[, (Callee)]*)]?
 
 where the first ``param`` is the number of the parameter it describes,
-``offset`` is the known access range of the paramenter inside of the function.
+``offset`` is the inclusive range of offsets from the pointer parameter to bytes
+which can be accessed by the function. This range does not include accesses by
+function calls from ``calls`` list.
 
 where each ``Callee`` decribes how parameter is forwared into other
 functions and looks like:
@@ -6836,7 +6838,27 @@
 
 The ``callee`` refers to the summary entry id of the callee,  ``param`` is
 the number of the callee parameter which points into the callers parameter
-with offset known to be inside of the ``offset`` range.
+with offset known to be inside of the ``offset`` range. ``calls`` will be
+consumed and removed by thin link stage to update ``Param::offset`` so it
+covers all accesses possible by ``calls``.
+
+Pointer parameter without corresponding ``Param`` is considered unsafe and we
+assume that access with any offset is possible.
+
+Example:
+
+.. code-block:: text
+
+    params: ((param: 2, offset: [0, 15]),(param: 3, offset: [5, 5], calls: ((callee: ^3, param: 5, offset: [-1, 1]))))
+
+Parameter #0 and #1 are either not pointers or access is unknown. Parameter #2
+will not be accessed outside of 16 bytes starting from the byte pointed by the
+parameter. ``calls`` is empty, so the parameter is either not used for function
+calls or ``offset`` already covers all accesses from nested function calls. Then
+function itself can access just a single byte of the parameter #3. Additional
+access is possible when the function calls ``^3``. The function increment or
+decrement parameter pointer and pass it as the argument #5 into ``^3``. This
+record itself does not tell us how ``^3`` will access the parameter.
 
 .. _refs_summary:
 
diff --git a/llvm/include/llvm/Analysis/StackSafetyAnalysis.h b/llvm/include/llvm/Analysis/StackSafetyAnalysis.h
--- a/llvm/include/llvm/Analysis/StackSafetyAnalysis.h
+++ b/llvm/include/llvm/Analysis/StackSafetyAnalysis.h
@@ -45,6 +45,12 @@
   void print(raw_ostream &O) const;
 
   /// Parameters use for a FunctionSummary.
+  /// Function collects access information of all pointer parameters.
+  /// Information includes a range of direct access of parameters by the
+  /// functions and all call sites accepting the parameter.
+  /// StackSafety assumes that missing parameter information means possibility
+  /// of access to the parameter with any offset, so we can correctly link
+  /// code without StackSafety information, e.g. non-ThinLTO.
   std::vector<FunctionSummary::ParamAccess> getParamAccesses() const;
 };
 
diff --git a/llvm/include/llvm/IR/ModuleSummaryIndex.h b/llvm/include/llvm/IR/ModuleSummaryIndex.h
--- a/llvm/include/llvm/IR/ModuleSummaryIndex.h
+++ b/llvm/include/llvm/IR/ModuleSummaryIndex.h
@@ -553,8 +553,8 @@
     unsigned AlwaysInline : 1;
   };
 
-  /// Describes the uses of a parameter by the range of offsets accessed in the
-  /// function and all of the call targets it is passed to.
+  /// Describes the uses of a parameter by the range of byte offsets of direct
+  /// access in in the function and by all of the call targets it is passed to.
   struct ParamAccess {
     static constexpr uint32_t RangeWidth = 64;
 
@@ -564,7 +564,7 @@
     struct Call {
       uint64_t ParamNo = 0;
       GlobalValue::GUID Callee = 0;
-      ConstantRange Offsets{RangeWidth, true};
+      ConstantRange Offsets{/*BitWidth=*/RangeWidth, /*isFullSet=*/true};
 
       Call() = default;
       Call(uint64_t ParamNo, GlobalValue::GUID Callee,
@@ -573,7 +573,7 @@
     };
 
     uint64_t ParamNo = 0;
-    ConstantRange Use{RangeWidth, true};
+    ConstantRange Use{/*BitWidth=*/RangeWidth, /*isFullSet=*/true};
     std::vector<Call> Calls;
 
     ParamAccess() = default;
diff --git a/llvm/lib/Analysis/StackSafetyAnalysis.cpp b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
--- a/llvm/lib/Analysis/StackSafetyAnalysis.cpp
+++ b/llvm/lib/Analysis/StackSafetyAnalysis.cpp
@@ -748,13 +748,16 @@
   return *Info;
 }
 
-// Converts a StackSafetyFunctionInfo to the relevant FunctionSummary
-// constructor fields
 std::vector<FunctionSummary::ParamAccess>
 StackSafetyInfo::getParamAccesses() const {
+  // Implementation transforms internal representation of parameter information
+  // into FunctionSummary format.
   std::vector<FunctionSummary::ParamAccess> ParamAccesses;
   for (const auto &KV : getInfo().Info.Params) {
     auto &PS = KV.second;
+    // Parameter accessed by any or unknown offset, represented as FullSet by
+    // StackSafety, is handled as the parameter for which we have no
+    // StackSafety info at all. So drop it to reduce summary size.
     if (PS.Range.isFullSet())
       continue;
 
@@ -763,6 +766,10 @@
 
     Param.Calls.reserve(PS.Calls.size());
     for (auto &C : PS.Calls) {
+      // Parameter forwarded into another function by any or unknown offset
+      // will make ParamAccess::Range as FullSet anyway. So we can drop the
+      // entire parameter like we did above.
+      // TODO(vitalybuka): Return already filtered parameters from getInfo().
       if (C.Offset.isFullSet()) {
         ParamAccesses.pop_back();
         break;