Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -1537,7 +1537,7 @@
   unsigned ArgNo = 0;
   for (Value *V : CS.args()) {
     if (!CS.paramHasAttr(ArgNo+1, Attribute::NonNull) &&
-        isKnownNonNull(V)) {
+        isKnownNonNullAt(V, CS.getInstruction(), DT, TLI)) {
       AttributeSet AS = CS.getAttributes();
       AS = AS.addAttribute(CS.getInstruction()->getContext(), ArgNo+1,
                            Attribute::NonNull);
Index: test/Transforms/InstCombine/call_nonnull_arg.ll
===================================================================
--- /dev/null
+++ test/Transforms/InstCombine/call_nonnull_arg.ll
@@ -0,0 +1,17 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+; InstCombine should mark null-checked argument as nonnull at callsite
+declare void @dummy(i32*)
+
+define void @test(i32* %a) {
+; CHECK-LABEL: @test
+; CHECK: call void @dummy(i32* nonnull %a)
+entry:
+  %cond = icmp eq i32* %a, null
+  br i1 %cond, label %is_null, label %not_null
+not_null:
+  call void @dummy(i32* %a)
+  ret void
+is_null:
+  unreachable
+}