Index: lib/Sema/SemaDeclAttr.cpp
===================================================================
--- lib/Sema/SemaDeclAttr.cpp	(revision 224006)
+++ lib/Sema/SemaDeclAttr.cpp	(working copy)
@@ -3136,6 +3136,51 @@
                          Attr.getAttributeSpellingListIndex()));
 }
 
+AlwaysInlineAttr *Sema::mergeAlwaysInlineAttr(Decl *D, SourceRange Range,
+                                              unsigned AttrSpellingListIndex) {
+  if (D->hasAttr<OptimizeNoneAttr>()) {
+    Diag(Range.getBegin(), diag::warn_attribute_ignored) << "'always_inline'";
+    return nullptr;
+  }
+
+  if (D->hasAttr<AlwaysInlineAttr>())
+    return nullptr;
+
+  return ::new (Context) AlwaysInlineAttr(Range, Context,
+                                          AttrSpellingListIndex);
+}
+
+MinSizeAttr *Sema::mergeMinSizeAttr(Decl *D, SourceRange Range,
+                                    unsigned AttrSpellingListIndex) {
+  if (D->hasAttr<OptimizeNoneAttr>()) {
+    Diag(Range.getBegin(), diag::warn_attribute_ignored) << "'minsize'";
+    return nullptr;
+  }
+
+  if (D->hasAttr<MinSizeAttr>())
+    return nullptr;
+
+  return ::new (Context) MinSizeAttr(Range, Context, AttrSpellingListIndex);
+}
+
+OptimizeNoneAttr *Sema::mergeOptimizeNoneAttr(Decl *D, SourceRange Range,
+                                              unsigned AttrSpellingListIndex) {
+  if (AlwaysInlineAttr *Inline = D->getAttr<AlwaysInlineAttr>()) {
+    Diag(Inline->getLocation(), diag::warn_attribute_ignored) << Inline;
+    D->dropAttr<AlwaysInlineAttr>();
+  }
+  if (MinSizeAttr *MinSize = D->getAttr<MinSizeAttr>()) {
+    Diag(MinSize->getLocation(), diag::warn_attribute_ignored) << MinSize;
+    D->dropAttr<MinSizeAttr>();
+  }
+
+  if (D->hasAttr<OptimizeNoneAttr>())
+    return nullptr;
+
+  return ::new (Context) OptimizeNoneAttr(Range, Context,
+                                          AttrSpellingListIndex);
+}
+
 static void handleAlwaysInlineAttr(Sema &S, Decl *D,
                                    const AttributeList &Attr) {
   if (checkAttrMutualExclusion<OptimizeNoneAttr>(S, D, Attr))
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp	(revision 224006)
+++ lib/Sema/SemaDecl.cpp	(working copy)
@@ -2154,6 +2154,12 @@
     NewAttr = S.mergeMSInheritanceAttr(D, IA->getRange(), IA->getBestCase(),
                                        AttrSpellingListIndex,
                                        IA->getSemanticSpelling());
+  else if (const auto *AA = dyn_cast<AlwaysInlineAttr>(Attr))
+    NewAttr = S.mergeAlwaysInlineAttr(D, AA->getRange(), AttrSpellingListIndex);
+  else if (const auto *MA = dyn_cast<MinSizeAttr>(Attr))
+    NewAttr = S.mergeMinSizeAttr(D, MA->getRange(), AttrSpellingListIndex);
+  else if (const auto *OA = dyn_cast<OptimizeNoneAttr>(Attr))
+    NewAttr = S.mergeOptimizeNoneAttr(D, OA->getRange(), AttrSpellingListIndex);
   else if (isa<AlignedAttr>(Attr))
     // AlignedAttrs are handled separately, because we need to handle all
     // such attributes on a declaration at the same time.
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp	(revision 224047)
+++ lib/CodeGen/CodeGenModule.cpp	(working copy)
@@ -769,9 +769,10 @@
     // OptimizeNone wins over OptimizeForSize, MinSize, AlwaysInline.
     assert(!F->hasFnAttribute(llvm::Attribute::OptimizeForSize) &&
            "OptimizeNone and OptimizeForSize on same function!");
-    // FIXME: Change these to asserts.
-    F->removeFnAttr(llvm::Attribute::MinSize);
-    F->removeFnAttr(llvm::Attribute::AlwaysInline);
+    assert(!F->hasFnAttribute(llvm::Attribute::MinSize) &&
+           "OptimizeNone and MinSize on same function!");
+    assert(!F->hasFnAttribute(llvm::Attribute::AlwaysInline) &&
+           "OptimizeNone and AlwaysInline on same function!");
 
     // Attribute 'inlinehint' has no effect on 'optnone' functions.
     // Explicitly remove it from the set of function attributes.
Index: test/SemaCXX/attr-optnone.cpp
===================================================================
--- test/SemaCXX/attr-optnone.cpp	(revision 224006)
+++ test/SemaCXX/attr-optnone.cpp	(working copy)
@@ -6,9 +6,21 @@
 int baz() __attribute__((always_inline)) __attribute__((optnone)); // expected-error{{'always_inline' and 'optnone' attributes are not compatible}}
 int quz() __attribute__((optnone)) __attribute__((always_inline)); // expected-error{{'optnone' and 'always_inline' attributes are not compatible}}
 
+__attribute__((always_inline)) int baz1(); // expected-warning{{'always_inline' attribute ignored}}
+__attribute__((optnone)) int baz1() { return 1; }
+
+__attribute__((optnone)) int quz1();
+__attribute__((always_inline)) int quz1() { return 1; } // expected-warning{{'always_inline' attribute ignored}}
+
 int bay() __attribute__((minsize)) __attribute__((optnone)); // expected-error{{'minsize' and 'optnone' attributes are not compatible}}
 int quy() __attribute__((optnone)) __attribute__((minsize)); // expected-error{{'optnone' and 'minsize' attributes are not compatible}}
 
+__attribute__((minsize)) int bay1(); // expected-warning{{'minsize' attribute ignored}}
+__attribute__((optnone)) int bay1() { return 1; }
+
+__attribute__((optnone)) int quy1();
+__attribute__((minsize)) int quy1() { return 1; } // expected-warning{{'minsize' attribute ignored}}
+
 __forceinline __attribute__((optnone)) int bax(); // expected-error{{'__forceinline' and 'optnone' attributes are not compatible}}
 __attribute__((optnone)) __forceinline int qux(); // expected-error{{'optnone' and '__forceinline' attributes are not compatible}}
 
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h	(revision 224006)
+++ include/clang/Sema/Sema.h	(working copy)
@@ -2005,6 +2005,12 @@
                               int FirstArg, unsigned AttrSpellingListIndex);
   SectionAttr *mergeSectionAttr(Decl *D, SourceRange Range, StringRef Name,
                                 unsigned AttrSpellingListIndex);
+  AlwaysInlineAttr *mergeAlwaysInlineAttr(Decl *D, SourceRange Range,
+                                          unsigned AttrSpellingListIndex);
+  MinSizeAttr *mergeMinSizeAttr(Decl *D, SourceRange Range,
+                                unsigned AttrSpellingListIndex);
+  OptimizeNoneAttr *mergeOptimizeNoneAttr(Decl *D, SourceRange Range,
+                                          unsigned AttrSpellingListIndex);
 
   /// \brief Describes the kind of merge to perform for availability
   /// attributes (including "deprecated", "unavailable", and "availability").
Index: include/clang/Basic/AttrDocs.td
===================================================================
--- include/clang/Basic/AttrDocs.td	(revision 224006)
+++ include/clang/Basic/AttrDocs.td	(working copy)
@@ -1264,7 +1264,8 @@
 specified function can improve the quality of the debugging information
 for that function.
 
-This attribute is incompatible with the ``always_inline`` attribute.
+This attribute is incompatible with the ``always_inline`` and ``minsize``
+attributes.
   }];
 }