[clang] Restrict Inline Builtin to non-static, non-odr linkage

Inline builtins have a very special behavior compared to other
functions, it's better if we keep them restricted to a minimal set of
functions.

Add a linkage check which prevents considering ODR definitions as inline
builtins.

Fix llvm#62958

Differential Revision: https://reviews.llvm.org/D148723

Author: serge-sans-paille

clang/lib/AST/Decl.cpp

@@ -3314,8 +3314,23 @@ bool FunctionDecl::isInlineBuiltinDeclaration() const {
     return false;
 
   const FunctionDecl *Definition;
-  return hasBody(Definition) && Definition->isInlineSpecified() &&
-         Definition->hasAttr<AlwaysInlineAttr>();
+  if (!hasBody(Definition))
+    return false;
+
+  if (!Definition->isInlineSpecified() ||
+      !Definition->hasAttr<AlwaysInlineAttr>())
+    return false;
+
+  ASTContext &Context = getASTContext();
+  switch (Context.GetGVALinkageForFunction(this)) {
+  case GVA_Internal:
+  case GVA_DiscardableODR:
+  case GVA_StrongODR:
+    return false;
+  case GVA_AvailableExternally:
+  case GVA_StrongExternal:
+    return true;
+  }
 }
 
 bool FunctionDecl::isDestroyingOperatorDelete() const {

clang/test/CodeGen/inline-builtin-comdat.c

@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -triple x86_64-windows -S -emit-llvm -disable-llvm-passes %s -o - | FileCheck %s
+// Inline builtin are not supported for odr linkage
+// CHECK-NOT: .inline
+
+double __cdecl frexp( double _X, int* _Y);
+inline __attribute__((always_inline))  long double __cdecl frexpl( long double __x, int *__exp ) {
+  return (long double) frexp((double)__x, __exp );
+}
+
+long double pain(void)
+{
+    long double f = 123.45;
+    int i;
+    long double f2 = frexpl(f, &i);
+    return f2;
+}