3 files changed, 21 insertions, 1 deletions
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index be59d88b73f..0d30f64b992 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -3046,6 +3046,14 @@ bool FunctionDecl::isReplaceableGlobalAllocationFunction(bool *IsAligned) const
   return Params == FPT->getNumParams();
 }
 
+bool FunctionDecl::isInlineBuiltinDeclaration() const {
+  if (!getBuiltinID())
+    return false;
+
+  const FunctionDecl *Definition;
+  return hasBody(Definition) && Definition->isInlineSpecified();
+}
+
 bool FunctionDecl::isDestroyingOperatorDelete() const {
   // C++ P0722:
   //   Within a class C, a single object deallocation function with signature
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index b23d9df5f4b..8e0604181fb 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -4621,8 +4621,15 @@ RValue CodeGenFunction::EmitSimpleCallExpr(const CallExpr *E,
 }
 
 static CGCallee EmitDirectCallee(CodeGenFunction &CGF, const FunctionDecl *FD) {
+
   if (auto builtinID = FD->getBuiltinID()) {
-    return CGCallee::forBuiltin(builtinID, FD);
+    // Replaceable builtin provide their own implementation of a builtin. Unless
+    // we are in the builtin implementation itself, don't call the actual
+    // builtin. If we are in the builtin implementation, avoid trivial infinite
+    // recursion.
+    if (!FD->isInlineBuiltinDeclaration() ||
+        CGF.CurFn->getName() == FD->getName())
+      return CGCallee::forBuiltin(builtinID, FD);
   }
 
   llvm::Constant *calleePtr = EmitFunctionDeclPointer(CGF.CGM, FD);
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 038078bbe88..57beda26677 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1840,6 +1840,11 @@ void CodeGenModule::SetFunctionAttributes(GlobalDecl GD, llvm::Function *F,
   else if (const auto *SA = FD->getAttr<SectionAttr>())
      F->setSection(SA->getName());
 
+  if (FD->isInlineBuiltinDeclaration()) {
+    F->addAttribute(llvm::AttributeList::FunctionIndex,
+                    llvm::Attribute::NoBuiltin);
+  }
+
   if (FD->isReplaceableGlobalAllocationFunction()) {
     // A replaceable global allocation function does not act like a builtin by
     // default, only if it is invoked by a new-expression or delete-expression.