diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -1922,7 +1922,8 @@
     A function with the ``ssp`` attribute but without the ``alwaysinline``
     attribute cannot be inlined into a function without a
     ``ssp/sspreq/sspstrong`` attribute. If inlined, the caller will get the
-    ``ssp`` attribute.
+    ``ssp`` attribute. ``call``, ``invoke``, and ``callbr`` instructions with
+    the ``alwaysinline`` attribute force inlining.
 ``sspstrong``
     This attribute indicates that the function should emit a stack smashing
     protector. This attribute causes a strong heuristic to be used when
@@ -1950,7 +1951,9 @@
     A function with the ``sspstrong`` attribute but without the
     ``alwaysinline`` attribute cannot be inlined into a function without a
     ``ssp/sspstrong/sspreq`` attribute. If inlined, the caller will get the
-    ``sspstrong`` attribute unless the ``sspreq`` attribute exists.
+    ``sspstrong`` attribute unless the ``sspreq`` attribute exists.  ``call``,
+    ``invoke``, and ``callbr`` instructions with the ``alwaysinline`` attribute
+    force inlining.
 ``sspreq``
     This attribute indicates that the function should *always* emit a stack
     smashing protector. This overrides the ``ssp`` and ``sspstrong`` function
@@ -1970,7 +1973,8 @@
     A function with the ``sspreq`` attribute but without the ``alwaysinline``
     attribute cannot be inlined into a function without a
     ``ssp/sspstrong/sspreq`` attribute. If inlined, the caller will get the
-    ``sspreq`` attribute.
+    ``sspreq`` attribute.  ``call``, ``invoke``, and ``callbr`` instructions
+    with the ``alwaysinline`` attribute force inlining.
 
 ``strictfp``
     This attribute indicates that the function was called from a scope that
diff --git a/llvm/lib/IR/Attributes.cpp b/llvm/lib/IR/Attributes.cpp
--- a/llvm/lib/IR/Attributes.cpp
+++ b/llvm/lib/IR/Attributes.cpp
@@ -2159,16 +2159,6 @@
 /// If the inlined function had a higher stack protection level than the
 /// calling function, then bump up the caller's stack protection level.
 static void adjustCallerSSPLevel(Function &Caller, const Function &Callee) {
-#ifndef NDEBUG
-  if (!Callee.hasFnAttribute(Attribute::AlwaysInline)) {
-    assert(!(!Callee.hasStackProtectorFnAttr() &&
-             Caller.hasStackProtectorFnAttr()) &&
-           "stack protected caller but callee requested no stack protector");
-    assert(!(!Caller.hasStackProtectorFnAttr() &&
-             Callee.hasStackProtectorFnAttr()) &&
-           "stack protected callee but caller requested no stack protector");
-  }
-#endif
   // If upgrading the SSP attribute, clear out the old SSP Attributes first.
   // Having multiple SSP attributes doesn't actually hurt, but it adds useless
   // clutter to the IR.
diff --git a/llvm/test/Transforms/Inline/inline_nossp.ll b/llvm/test/Transforms/Inline/inline_nossp.ll
--- a/llvm/test/Transforms/Inline/inline_nossp.ll
+++ b/llvm/test/Transforms/Inline/inline_nossp.ll
@@ -35,3 +35,18 @@
   %2 = call i32 @nossp_alwaysinline()
   ret i32 %2
 }
+
+; The alwaysinline attribute can also appear on the CallBase (ie. the call
+; site), ie. when __attribute__((flatten)) is used on the caller. Treat this
+; the same as if the caller had the fn attr alwaysinline and permit inline
+; substitution, despite the mismatch between caller and callee on ssp attrs.
+;
+; Curiously, the always_inline attribute on a CallInst is only expanded by the
+; inline pass, but not always_inline pass!
+define i32 @nossp_alwaysinline_caller() {
+; CHECK-INLINE-LABEL: @nossp_alwaysinline_caller(
+; CHECK-INLINE-NEXT:    ret i32 42
+;
+  %1 = call i32 @ssp() alwaysinline
+  ret i32 %1
+}