Refine the constraint for isInlineBuiltinDeclaration

Require it to be always_inline, to more closely match how _FORITFY_SOURCE
behaves.

This avoids generation of `.inline` suffixed functions - these should always be
inlined.

Author: serge-sans-paille

clang/lib/AST/Decl.cpp

@@ -3176,7 +3176,8 @@ bool FunctionDecl::isInlineBuiltinDeclaration() const {
     return false;
 
   const FunctionDecl *Definition;
-  return hasBody(Definition) && Definition->isInlineSpecified();
+  return hasBody(Definition) && Definition->isInlineSpecified() &&
+         Definition->hasAttr<AlwaysInlineAttr>();
 }
 
 bool FunctionDecl::isDestroyingOperatorDelete() const {

clang/test/CodeGen/memcpy-nobuiltin.inc

@@ -2,7 +2,7 @@
 extern void *memcpy(void *dest, void const *from, size_t n);
 
 #ifdef WITH_DECL
-inline void *memcpy(void *dest, void const *from, size_t n) {
+inline __attribute__((always_inline)) void *memcpy(void *dest, void const *from, size_t n) {
   char const *ifrom = from;
   char *idest = dest;
   while (n--)
@@ -11,7 +11,7 @@ inline void *memcpy(void *dest, void const *from, size_t n) {
 }
 #endif
 #ifdef WITH_SELF_REFERENCE_DECL
-inline void *memcpy(void *dest, void const *from, size_t n) {
+inline __attribute__((always_inline)) void *memcpy(void *dest, void const *from, size_t n) {
   if (n != 0)
     memcpy(dest, from, n);
   return dest;